The Fuel and Engine Bible - how engines work including 2 stroke, 4 stroke and wankel (rotary) engines, fuel, octane rating, power, bhp, gas types and grades, carburettors, fuel injection, tuning, tweaking, nitrous, turbos, superchargers, chipping, hybrids, how to keep your engine running at peak fitness and much more.

Page 2

Page 3

And so to fuel (or gasoline or petrol)

Petrol (or gasoline if you're American) is a distilled and refined oil product made up of hydrogen and carbons - a hydrocarbon. A long-chain hydrocarbon to be exact (so don't get it on your skin - its carcinogenic). It's designed to be relatively safe to handle, if you're careful. ie. it doesn't spontaneously combust without extreme provocation. When you have a petrol fire, it's not the petrol itself that is burning, it's the vapour, and this is the key to fueling an engine. The carburettor or fuel injectors spray petrol into an air stream. The tiny particles of petrol evaporate into a vapour extremely quickly, and combined in a cloud with the air, it becomes extremely combustible. The smaller the particles from the carburettor jet or fuel injector, the more efficiently the mixture burns.

This will be replaced by the player.

Detonation, pre-ignition, pinking, pinging and knocking.

Remember I said petrol doesn't spontaneously combust? Well it can if the conditions are right, and the conditions are extreme heat and pressure - exactly the conditions you find in the combustion chamber. When this happens, it's called detonation or pre-ignition. Diesel engines rely on this process because they don't have a spark plug in the traditional sense of the word. However in petrol engines, when this happens (also known as dieseling), it's a Very Bad Thing. Engines are designed to have the fuel-air mix burn at a fixed point in the cycle, not explode randomly. Whilst it might look like an explosion, if you could film it on a super high-speed camera, you'd see the mixture actually burns up very quickly rather than exploding. The video on the right is just that - in-cylinder video of the 4 stroke combustion cycle. The intake valve is on the right, the exhaust valve on the left. Detonation, dieseling or pre-ignition are all terms for what happens when the fuel-air mix spontaneously explodes rather than burning. Normally this happens when the mixture is all fouled up, and the engine is running hot. The temperature and pressure build up too quickly in the combustion chamber and before the piston can reach the top of its travel, the mixture explodes. This explosion tries to counteract the advancing piston and puts an enormous amount of stress on the piston, the cylinder walls and the connecting rod. From the outside of the engine, you'll hear it as a knocking or pinging sound. The precise sound is very hard to describe because every engine sounds slightly different when it happens. But the best way I can describe it is a constant 'toc toc toc' type knocking sound.

Video credit: Original source unknown. Video also available on YouTube and Google Video.

Compression ratio.

The compression ratio of an engine is the measurement of the ratio between the combined volume of a cylinder and a combustion chamber when the piston is at the bottom of its stroke, and the same volume when the it's at the top of its stroke. The higher the compression ratio, the more mechanical energy an engine can squeeze from its air-fuel mixture. Similarly, the higher the compression ratio, the greater the liklihood of detonation.

Octane ratings - how to stop detonation

So you know that a fuel-air mix, given the right conditions, can spontaneously combust. In order to control this property, all petrols have chemicals mixed in with them to control how quickly the fuel burns. This is known as the octane rating of the fuel. The higher the rating, the slower and more controlled the fuel burns.
Put on the geek-shades for a moment and I'll explain octane in more depth. If you don't like being blinded by science, skip down a few paragraphs. For the rest of you, octane is measured relative to a mixture of isooctane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane. An 87-octane gasoline has the same knock resistance as a mixture of 87% isooctane and 13% n-heptane. The octane value of a fuel used to be controlled by the amount of tetraethyl lead in it, but in the 70s and 80s when it became apparent that lead was pretty harmful, lead-free petrol appeared and other substances were introduced to control octane instead.

Measuring octane - RON, MON and the difference between America and the rest of the world.

octane decal or sticker Just so you know, the octane number is actually an imprecise measure of the maximum compression ratio at which a particular fuel can be burned in an engine without detonation. There are actually two numbers - RON (Research octane number) and MON (Motor Octane Number). The RON simulates fuel performance under low severity engine operation. The MON simulates more severe operation that might be incurred at high speed or high load and can be as much as 10 points lower than the RON. In Europe, what you'll see on the petrol pumps is the RON. However, in America, what you'll see on the petrol pump is usually the "mean" octane number - notified as (R+M)/2 - the average of both the RON and MON. This is why there is an apparent discrepancy between the octane values of petrol in America versus the rest of the world. Euro95 unleaded in Europe is 95 octane but it's the equivalent of American (R+M)/2 89 octane.
In America, low altitude petrol stations typically sell three grades of petrol with octane ratings of 87, 89 and 91. High altitude stations typically also sell three grades, but with lower values - 85, 87 and 89.

What factors affect detonation?

There's a bunch of things that can affect how likely an engine is to have detonation problems. The common ones are ambient air temperature, humidity, altitude, your engine's ability to stay cool (ie. the cooling system) and spark timing. Fortunately, nowadays the engine management system of modern cars can compensate for almost all of these by advancing and retarding the ignition timing. This is where the computer slightly adjusts the point in the ignition cycle at which the spark is generated at the spark plug. With older engines that used mechanical points to send current to the spark plugs, adjusting the timing was a manual affair that involved adjusting the distributor cap orientation.
Knock sensors. Most modern cars have knock sensors screwed into the engine at multiple places. These actually detect the vibration or shock caused by detonation (rather than trying to detect the sound) and can signal the engine management system to change the ignition timing to reduce or eliminate the problem.

Octane and altitude

The higher the altitude above sea level, the lower the octane requirement. As a general rule of thumb, for every 300m or 1000ft above sea level, the RON value can go down by about 0.5. For example an 85 octane fuel in Denver will have about the same characteristics as an 87 octane fuel on the coast in Los Angeles. As a practical example of this, I currently live in Salt Lake City which is at around 4,200ft. We travel to Las Vegas from time to time which is at around 2,000ft. Our Subaru has a minimum octane requirement of 89 at sea level - so about 87 where we live. Last time we drove to Vegas, the petrol station we stopped at had run out of 'premium' products so we had to fill up with 85 octane. This, combined with the drop in altitude caused the 'check engine' light to come on because we'd effectively taken the engine from 87 octane at altitude to the equivalent of 83 octane at altitude - way below the minimum required by our car.
The following graph gives a rough idea of how the three main grades of petrol in America perform with respect to octane at altitude.

Octane and power

It's a common misconception amongst car enthusiasts that higher octane = more power. This is simply not true. The myth arose because of sportier vehicles requiring higher octane fuels. Without understanding why, a certain section of the car subculture decided that this was because higher octane petrol meant higher power.
The reality of the situation is a little different. Power is limited by the maximum amount of fuel-air mixture that can be jammed into the combustion chamber. Because high performance engines operate with high compression ratios they are more likely to suffer from detonation and so to compensate, they need a higher octane fuel to control the burn. So yes, sports cars do need high octane fuel, but it's not because the octane rating is somehow giving more power. It's because it's required because the engine develops more power because of its design.
There is a direct correlation between the compression ratio of an engine and its fuel octane requirements. The following table is a rough guide to octane values per engine compression ratio for a carburettor engine without engine management. For modern fuel-injected cars with advanced engine management systems, these values are lowered by about 5 to 7 points.

Compression ratio	Octane
5:1	72
6:1	81
7:1	87
8:1	92
9:1	96
10:1	100
11:1	104
12:1	108

Octane and gas mileage

Here's a good question : can octane affect gas mileage. The short answer is absolutely, yes it can, but not for the reasons you might think. The octane value of a fuel itself has nothing to do with how much potential energy the fuel has, or how cleanly or efficiently it burns. All it does is control the burn. However, if you're running with a petrol that isn't the octane rating recommended for your car, you could lose gas mileage. Why? Lets say your manufacturers handbook recommends that you run 87 octane fuel in your car but you fill it with 85 instead, trying to save some money on filling up. Your car will still work just fine because the engine management system will be detecting knock and retarding the ignition timing to compensate. And that's the key. By changing the ignition timing, you could be losing efficiency in the engine, which could translate into worse gas mileage. Again as a practical example, my little tale above about our trip to Vegas on low octane gas. (Whether you want to believe some bloke on the internet or not is up to you). On the low octane gas on the trip down, we could barely get 23.5mpg out of the Subaru. Once I was able to fill it up again with premium at the recommended octane rating, we got 27.9mpg on the way back. A difference of 4.4mpg over 450 miles of driving.
Doing the maths, you can figure out that by skimping on the price during fill-up, you may save a little money right there and then, but it costs in the long term because you're going to be filling up more often to do the same mileage. My advice? Do what the handbook tells you. After all it's in the manufacturers better interests that you get the most performance out of your car as you can - they don't want you badmouthing them, and in this day and age of instant internet gratification, you can bad-mouth a large company very quickly and get a lot of publicity.

Octane boosters

In some extreme cases, the highest octane fuel available might not solve a knocking or detonation problem. That's normally a symptom of a deeper problem in the engine involving carbon deposits on the cylinder heads, bad spark timing, faulty engine management systems or similar. In these cases, some people choose to add octane booster to their petrol. Basically you fill the tank as normal, then put in a measured amount of octane booster and it further raises the octane level in an attempt to stop the detonation. One of the downsides of this is that it can make the engine harder to start from cold, because the octane booster has made the fuel so much less volatile that it's hard to get it to ignite on the first couple of strokes. Products like Klotz and Redex octane boosters are readily available over the counter in most auto parts stores. Octane boosters are typically used by mis-educated motorcyclists who believe the myth (explained above) that high octane = more power.
Octane boosters tested by Fifth Gear. To try to lay the myth about octane boosters giving more power to bed for once and for all, in 2007 the UK TV show Fifth Gear picked four likely candidates and subjected them to rigorous testing. They picked Nitro Hot Shot, NOS Race Only Octane Booster, Wynn's Power Booster and STP Power Booster. All four products make the usual wild claims about increased gas mileage, more bhp and so on and so forth. They took the products to Oxford Brooks University's engine testing lab. The engine was static-mounted so measurements were made at the flywheel. The throttle was computer controlled so they could reproduce the same scenario over and over again. They first did a baseline test to find out peak bhp with regular unleaded petrol. This involved various constant-throttle settings as well as acceleration and deceleration testing, and a 1-hour constant-speed run to emulate driving on a motorway in clear traffic. Each product was tested using the identical setup, with a 15 minute 'pure' petrol flush being used in between each test to ensure there was no cross-contamination. The results were interesting. Nitrox Hot Shot, NOS Race Only Octane Booster and Wynn's Octane Booster all reduced the overall power by 2bhp. STP Power Booster reduced it by 6%. Now remember this was measured at the flywheel so by the time you induce all the drag of the gearbox and driveline into that equation, you'd likely be looking at a 5% to 10% drop at the wheels. Impressive results for products that claim to increase your engine's power.

In England, octane boosters are typically also sold as "lead replacements" or "4 star additive". A lot of European cars relied on the lead in 4-star petrol for the increased octane. Lower octane unleaded fuels caused a lot of problems when they first appeared, especially with cars that didn't have engine management systems. Knocking and detonation became evident in a lot of cars and for some reason French and German engines were more susceptible than most. Dumping a shot of octane booster in the tank when filling up solved the problem by raising the RON a few points to make it the equivalent of what old leaded petrol had been. Eventually, by the late 90s, most English and European petrol stations introduced LRP - lead replacement petrol, and the problem went away. Well. Sort of......

Picture credits: Halfords and Channel 5

Lead Replacement Petrol (LRP) and valve seats

Whilst LRP solved the problem of lower octane unleaded petrol, it introduced a new problem. The lead in leaded petrol also had a secondary function and that was to lubricate the valve seats - the top of the engine block where the valves "park" when not being opened by the cams. With the advent of LRP, detonation went away but the chemicals used to increase octane didn't have any lubricating function. Some older engines started to suffer from increased wear to the valve seats, to the point where the valves could no longer properly close and seal the intake and exhaust ports. There were a couple of high profile cases before I left for America in 2001 but I've never been able to find out the end result. If you have any information on what happened in these cases, drop me a line and I'll include the info here.

The supermarket petrol debate

tesco petrol station During the 90s, in England, supermarkets started a price war with the mainstream fuel vendors by opening their own petrol stations and undercutting the Esso's and Shell's of the world by as much as 5%. People flocked to these cheap outlets without doing any proper research and after a couple of years, a lot of vehicles began to suffer as a result. There's an old saying that begins "if it's too good to be true....." In the case of supermarket petrol, there was an obvious reason why it was cheaper - it was the lower grade fuel that the mainstream outlets wouldn't take. Stuff which had been rejected in quality control, or had less additives and detergents than what you might get from Texaco or Philips66. As a result, engines started clogging up and failing emissions test. Gas mileage went down. Engines became lumpy and rough running and eventually the supermarkets were forced to fall in line with the Big Boys, so much so that nowadays they're normally less than 1% cheaper.
Skip forwards to 2005 and the first summer of high fuel prices in America. Lo and behold, supermarkets started to sprout petrol stations and a lot of people were in the same "cheap fuel" euphoria that the English were in 10 years previously. The American market did it slightly differently though. Whereas in England, they started out with utterly sub-standard petrol, in the US it seems to be down to the additive and detergent blends (the same system used in the UK now). Typically, pipeline companies pipe in and store the petrol for distribution by filling up the various trucks that deliver to the various petrol stations. So branded and unbranded trucks are filled from the same supply. The difference is that when a truck from one of the majors fills up, they stop at the small company pump where that company's special detergent and additive mix is then pumped into the truck prior to the main fill-up. I'm not entirely clear on the percentages here, but I've had emails from some readers claiming that it's as little has half a gallon of branded additive for each 9000 gallon truck (0.0028% additive).
This raises an interesting question then - are you better off to go branded, or to use the cheapest stuff you can find and then every couple of months, get a bottle of Chevron Techron additive (or whatever) and run that through your car?
costco petrol station As a substitute for genuinely cheaper fuel, a lot of European supermarket chains now offer cheaper fuel at a price. The catch is that you have to shop with them. Once you buy a certain amount of stuff from their store, they'll knock off a percentage of the price of petrol if you buy it from them. The fuel isn't the cheap and nasty sub-standard stuff of yesteryear that they used to use - it's good, mainstream product. But they can hide the price drop in the cost of the groceries and other items you buy in store. From your perspective, you save £2 a tank when filling up. From the store's perspective, you just spent £100 in shopping so giving you £2 back on your tank of gas is pocket change.
In America, some of the big-box chains, like CostCo and Sam's Club are now doing the same thing. Rather than go the "dodgy crappy petrol" route, they're offering discounted petrol for shopping in their stores, discounting the petrol by a couple of cents per gallon as long as you've bought more than $50 of products from them.

Fuel filters - without them, all this means nothing

plastic fuel filter As all this information about petrol and gasoline is starting to run out of your ears, it's worth bringing up the topic of fuel filters. Without fuel filters, none of this information on petrol is worth anything. Why? In an ideal world, every time you fill your tank, the petrol would come from brand new underground tanks, through brand new hoses and nozzles, down a pristeen filler tube into a brand new gas tank. However, back in the real world, that simply isn't the case. Tiny bits of metal flake off components. Things rust. Grit and grime gets into the fuel through many different sources. For the most part, this sediment settles at the bottom of the underground tanks in a petrol station, and at the bottom of the petrol tank in your car. If you're unlucky enough to fill up just after the petrol station has received a load of fuel from a tanker though, all that sediment will be nicely mixed into the petrol, and you'll get a petrol-sediment mix in your petrol tank. Similarly, if you insist on running your petrol tank down to the 'E' mark on the fuel gauge, you'll be sucking up petrol-sediment mix from the bottom of your own tank. It's a good job then that the men in lab coats decided to put in-line fuel filters in your car. These are relatively simple little devices that come in two basic flavours.

Carburettor engine fuel filters. These are the plastic in-line fuel filters. They look like a little plastic container with a wavy yellow pad in them. They're typically designed to have the fuel sucked through them via a mechanical crank-driven fuel pump up near the carburettor. In some tuner vehicles you'll find this has been replaced with a tasty little aluminium item, usually anodised in a nice colour, designed to make it nearly impossible to find.

Fuel injection filters. These are the metal cannister-type fuel filters that are normally buried under the car somewhere. They're designed to have the fuel pushed through them by an electric high-pressure fuel pump, and so the pressure in the fuel line is much higher. This is why they're made of metal. Internally, the filter material is normally finer too.

Why filter the fuel? Won't the debris just burn?

Generally speaking, unless it's metal filings, then yes, most debris that you'd find in a fuel system would burn during combustion but that's not the problem. The problem is getting the fuel into the engine in the first place. Further back up this page you (hopefully) learned about carburettors and fuel injectors. The one thing common to both is the tiny hole at the end of the line where the fuel is finally atomised into the air. A good sized grain of sand would be all it took to block that tiny hole and once that happens, it doesn't matter how clever your engine is, it won't be getting any petrol. That is why you have to filter fuel - to keep particulates from clogging areas of the fuel system vital to its operation.
Most manufacturers will tell you that fuel filters are sealed-for-life, or life-time-of-the-car items. Excuse my French but that's total bollocks. In normal operating conditions, in 'first-world' countries, you should change your fuel filter every 75,000 miles (120,000km) or so. If you're into extreme motoring, like round-the-world touring, or working in 'third-world' countries, your fuel filter might need changing as much as every 5,000 miles. That's not a slur on those countries, it's just a fact that the cleanliness of petrol station holding and delivery systems isn't really a hot priority in those countries. Plus, if you're involved in that sort of driving, chances are most of your petrol will come from a rusty metal jerry can.

Why change the filter?

The job of an in-line fuel filter is to filter out sediment and particulates in the petrol that might otherwise cause problems further down the line in the engine. If you think about it, the average car probably has 40 to 50 litres of petrol go through the fuel filter every week. It stands to reason then that eventually the filter is going to become clogged with debris. Once your filter gets clogged, you start to get all sorts of followon problems. In carburettor cars, you'll get sporadic and weak fuel supply which will lead to a stuttering engine, or an engine that seems to have no power under acceleration. In a fuel injection system where the fuel line pressures are much greater, a clogged filter can lead to a burned out petrol pump or a blown fuel line connection on top of the fuel starvation problems.
So just bear it in mind when you get to around 75,000 miles. If you're doing your own servicing, change the filter. If you're using a dealer, insist it gets changed despite their protests (and they will protest).

Where is my fuel filter?

You might as well ask me to explain Unified Field Theory to you here. Locating the fuel filter on any vehicle is a dark art known only to the robot that put your car together. The filter can literally be anywhere in between the tank and the engine. For carburettor engines it's most likely to be in the engine bay, probably with 50cm of where the fuel line comes up from under the car, and clipped to some other tube or cable. For injection filters, it's most likely to be attached to the chassis or a suspension component underneath the car at the back axle, close to the fuel pump and petrol tank.

The 'sock' filter.

More often than not, there will be a mesh 'sock' on the pickup tube inside the petrol tank itself. This is a much trickier filter to change as it's a sort of pre-filter to catch the really large stuff. For the most part, these mesh filters don't block easily - anything sucked up against them will normally wash off with the natural movement of the petrol in the tank. Where it's possible to change the external filters yourself, doing the internal one is probably a job best left to a decent mechanic.

The carburettor internal filter.

Some carburettors have a last line of defence in the form of a metal gause filter just inside the fuel intake. If you take the fuel line off a carburettor and peer inside, that's the most likely place for this to be if there is one. It's worth knowing about this little joy because if you go to all the trouble of changing your other in-line filter(s) and still have a fuel starvation problem, it could be this last little bugger that's blocked. Now you know.

The magnet-on-your-fuel-line gimmick, only with a twist (thank you M.Night Shyamalan).

Elsewhere on this page you'll see how skeptical I am about the magnet-on-your-fuel-line gimmick. Generally speaking, these are a complete scam, trying to tempt you with wild claims of increased gas mileage and more power. That being said, there is one manufacturer who sells a product which entirely makes sense. FilterMAG do magnetic sleeves for engine oil filters (see magnetised oil traps) but they now also do the same sort of sleeve for fuel filters. The idea is really simple - stick a bunch of powerful rare-earth magnets on the outside of your fuel filters, and any metal particles in your fuel system will end up stuck to the inside of the filter because of the magnets outside. I know from experience that FilterMAG's oil filter product works a charm, so I have no reason to believe their petrol filter magnet would work any differently. My advice - if you're serious about the cleanliness of your fuel, or you know you're going to be taking your car or bike somewhere where the fuel supply might be dodgy, grab one of these FilterMAG products and stuff it on your in-line fuel filter for peace of mind. FilterMAG fuel filter magnet.

E85 Ethanol - the magic bullet?

With the spiralling cost of fuel prices brought on by George Bush's "War On Terror", people are looking at everything to get cheaper fuel, and one of the silver bullets seems to be E85 Ethanol-blend gasoline. I say 'seems to be' because once you do some research, which is what you're doing right here by reading this, you'll learn it's not quite the magic solution everyone would have you believe.
E85 is a blend of regular unleaded petrol with between 70% and 83% ethanol depending on the geographic location and time of year. (If you must know, Google for ASTM D 5798-99). Simply blending ethanol and petrol normally results in a product with too low a vapour pressure, especially in the winter, which is why it is a process best left to people in white labcoats in refineries.
It's designed for so-called Flexible Fuel vehicles, and as such has been classified by the US Department of Energy as an alternative fuel. The facts on E85 are a little hard to come by, so I've tried to collect together and put as many as I can right here so that you, dear reader, can try to cut to the chase. So what is a flexible fuel vehicle (FFV)? Well, it's a vehicle with an engine and emissions system designed to be able to run on a blend of unleaded petrol and ethanol up to a maximum of 85% ethanol. If E85 isn't available, you can run them on just plain old petrol though. If you read all the hoopla surrounding E85, you'll see this statement crop up time and time again: "It is a renewable source of energy and reduces the crude oil imports needed to fuel America's transportation system. Ethanol is a clean, environmentally friendly fuel.". Weeeeelllllll yes. But more specifically, "sort of". It's true that it is partly based on a renewable source of energy - ethanol is basically distilled corn oil (or wheat, barley, or potatoes. Brazil, the world's largest ethanol producer, makes the fuel from sugarcane), and yes, it's a cleaner and slightly more environmentally friendly fuel. There's a few 'buts' to go with all this, and they're a big 'buts' - of Jennifer Lopez proportions. First, there isn't enough farmland to grow enough corn to produce enough ethanol to meet gasoline demands, and it wouldn't be a good use of it even if there was. Second, there's a huge hidden cost in water - it takes 10 tons of water to process 1 ton of grain for ethanol [Ref: Plan B 2.0: Rescuing a Planet Under Stress and a Civilization in Trouble by Lester R Brown. ISBN 0393328317]. Third, in 2007, in a report on the impact of biofuels, the Organization for Economic Cooperation and Development (OECD) said biofuels may "offer a cure that is worse than the disease they seek to heal"."The current push to expand the use of biofuels is creating unsustainable tensions that will disrupt markets without generating significant environmental benefits," the OECD said. "When acidification, fertiliser use, biodiversity loss and toxicity of agricultural pesticides are taken into account, the overall environmental impacts of ethanol and biodiesel can very easily exceed those of petrol and mineral diesel," it added. And finally, in bold because it's the important part of this paragraph. E85 Ethanol-blend fuel has horrible gas mileage.
What does this mean to you? Well it means you'll need a lot more of it for a start. Sure it may be cheaper than regular petrol, but there's a reason - it's a terrible way to run a vehicle. Even the governments own figures back that statement up. Check out one of their lists of flexible-fueled vehicles for yourself. On average, putting E85 in a flexible fuel vehicle will return a nauseating 25% worse gas mileage. E85 doesn't burn as efficiently as regular petrol because it contains less energy per volume - 75,760btu per gallon as oppose to 115,400btu per gallon for plain old petrol. This accounts for the 30% increase in the amount of fuel required in the fuel-air mix during combustion, and the corresponding drop in gas mileage. All this comes with an average drop of only 10% in greenhouse gas emissions. If you go by historical precedent, and assume we all move to FFV's, the income from regular petrol will drop so the oil companies will simply increase the cost of E85. At that point, you're getting terrible gas mileage but paying what you used to for just plain vanilla unleaded petrol. Remember - nothing is free. Of course this doesn't need to be the case. E85's higher octane can allow the use of higher compression, more efficient engines (if optimized for use on it). Look at the race car teams - a lot of racing engines run on pure ethanol. And when engineered to take advantage of it, high-compression, high-efficiency engines can reduce the gas-mileage deficit to about 10% less than their petrol counterparts, which is much closer. But for ethanol to be successful it must be priced below petrol so that the cents per mile cost is favorable taking into account the drop in economy.

But what about Brazil?

For a while now, Brazil (the country, not the Terry Gilliam film) has managed to be largely independent of the world's fluctuating oil prices. By law, all Brazillian petrol must be at least 25% ethanol - E25 - created from sugar-cane-fed biorefineries. By 2007, almost all cars available in Brazil ought to be able to run on 100% ethanol. (It's worth noting that Ethanol-only cars were sold in Brazil in significant numbers between 1980 and 1995). No longer dictated-to by Big Oil, the price of their E100 is relatively low and thus it offsets the lower gas-mileage quite nicely. One argument put forth in America is that using E85 will reduce the reliance on foreign imports - specifically oil. But you need to look at the whole picture. E85 comes from corn, currently a crop used to feed people. Assuming that America has enough spare capacity to farm corn for E85 for the current demand, what happens when more people start using it? You can't increase farmland, or drop production of corn for food, so the next alternative is importing it. At which point, even using E85, you become dependent on foreign imports again. Brazil doesn't have this problem because their system is in balance and so they supply themselves with enough surplus to export their product. Most likely to America.

Clean exhaust - it depends on your definition of the word "clean".

Something that isn't widely publicised is the difference in emissions between corn-based ethanol, as used in America, and sugar-based ethanol, as used in Brazil. We're all told that ethanol blend fuels produce cleaner exhaust and with sugar-based ethanol, that's absolutely true. Even with corn-based ethanol, the gasses measured at an emissions check are lower (about 25% less CO₂), which still looks good. But there is something an ethanol E85 vehicle will produce through the exhaust that might surprise you. The exhaust gas contains acetaldehyde (CH₃CHO) and lots of it, especially if the fuel source or combustion process is contaminated with water (like cold-start condensation). Acetaldehyde is a known carcinogen (source, source) and suspected neurotoxin (source), and when exposed to its vapors, you or I would likely develop irritation of the eyes, skin and the respiratory tract. In fact, Acetaldehyde is ranked as one of the most hazardous compounds (worst 10%) to ecosystems and human health. It's obvious why this isn't widely publicised, but then you might ask the question "why don't we see this in the emissions test?". Simple. The emissions test doesn't look for it. You can't detect and measure something you're not looking for.
But wait - it gets better. The corn-based ethanol production process consumes more fossil fuel energy than ethanol's actual calorific value. In other words, to produce a gallon of ethanol to be used in E85, it takes more fossil fuel energy than you could simply get by putting a gallon of refined non-blend petrol in your car. And as you know, regular petrol also gives better economy.

E85 in non-flexible fuel vehicles

Two words : rotting seals. And I'm not talking about dead sealife. E85 is pretty acidic, and stuffing it in your regular petrol-engined car will do no end of damage to it. Apart from the spark timing and the fuel-air ratio being totally different, E85 has a whopping 105 octane rating to deal with the pre-igntion problems of having 30% more fuel in the fuel-air mix during combustion. The seals and gaskets in FFVs are designed to withstand the acidic deposits that E85 generates during combustion. Generally speaking, FFVs are manufactured to eliminate all bare aluminium, rubber and magnesium parts - all items which E85 is known to rot, and all items which a normal engine has by the bucketload. Another problem with E85 is that it's electrically conductive. Regular petrol fuel pumps aren't really designed to work with a conductive fuel, so using E85 with one could result in a fuel fire where the petrol is not only the fuel for the fire, but the electrical path for the spark. FFV fuel lines aren't made of rubber, but typically stainless steel lined with plastic.
So you may get cheaper petrol but you'll get worse gas-mileage and a broken car, with the possible bonus of a raging E85-fueled inferno to boot. However, there is a fly in the ointment here, and it is E10. Because of petrol company practices (see below), most fuel-injected engines designed and built since 1988 are already somewhat adapted to using ethanol, just not in the percentage you find in E85.

E10: you're using it right now

It's not widely known but a lot of petrol companies now blend up to 10% ethanol into their petrol products without really admitting to it, much less advertising the fact. If you've noticed your car runs somewhat less than the advertised gas mileage, that's part of the reason. Most of the gasoline in California is currently 5.7% ethanol (2% oxygen). Ethanol is blended into petrol for a variety of reasons including

as an oxygenate to reduce CO and HC emissions
an octane booster
to provide volume in place of MTBE

There's nothing wrong or underhanded about this, it's just a cost effective means to legitimate ends. So if the EPA tells you you should be getting 20mpg city and you're only getting 18mpg, even driving with a feather right foot, it's not you, it's the petrol companies. 10% ethanol blend will rob you of about 5% gas mileage, and EPA figures assume a pure non-ethanol petrol. Apart from the emissions regulations, money is a factor in ethanol blending - more product that is cheaper to produce but sold for the same price. You can bet your bottom dollar (or euro) that the European refineries are doing exactly the same thing.

Tax credits, subsidies and tariffs - the real story behind E85.

So given the (obscured) facts about corn-based ethanol, why the big push in America to go to E85? Simple. Money. The government is offering tax credits to the big car manufacturers to produce FFVs, even if none of them ever run on E85. Similarly, tax credits are now offered to the big oil companies to product E85 ethanol blend, even if they don't actually sell it. And when they do sell it, it will make the more money because you and I will need more of it to go the same distance. Finally, corn growers receive federal subsidies for growing corn for ethanol production. Couple that with the 54¢ per gallon tariff that is currently levied on Brazillian imports, and it shows how the corn-based ethanol has cornered the American market and is keeping the cheaper, cleaner, sugar-cane ethanol at bay.

What's that you say? You want fuel efficiency and less cost?

Well that's the conundrum isn't it? The oil and car companies aren't going to give stuff away free. So you have to choose. Do you want less cost at the point where you're putting the petrol into your car, or less cost-of-ownership? It's like comparing financial planning. If you get a flexible fuel vehicle, your immediate cost is much less - you could be spending 30% less per fill-up. But the long-term costs become negligible because of the bad gas mileage. On the other hand, if you take the long term investment point of view, you should be looking at vehicles like the VW Polo Bluemotion. It's a three-cylinder turbodiesel, which means at the point of filling it up, you'll actually be spending more than a regular petrol vehicle. But it returns 70mpg (max), so you'll be visiting the petrol station a lot less frequently. Don't understand the maths? Ok, lets lay it out.
I'm going to assume plain fuel costs here, so I'm not factoring in insurance, wear and tear, initial cost of the vehicle etc. Ready? Okay, we're going to compare two vehicles. Each drives 15,000 miles a year and each has a 16 gallon fuel tank. The owners of these vehicles are Barbie and Ken, and to be suitably sexist, Barbie has a pink VW Polo and Ken has a blue Ford Crown Victoria. They both fill up when the tank gets to 3 gallons left, so they drive 13 gallons at a time.

ken Ken
15,000 miles = 1250 gallons at 12mpg on E85.
1250 gallons = about $2300 assuming about $1.85 a gallon.
Ken stops and fills up every 156 miles.

barbie Barbie
15,000 miles = 225 gallons at 66.5mpg (split the values of 60mpg and 73mpg for city and highway) on diesel.
225 gallons = about $787 assuming about $3.50 a gallon.
Barbie stops and fills up every 864 miles.

So whilst Ken pays much less each time he fills up, he's filling up nearly 6 times as often, and at the end of the year, he's spent a whopping $1500 more in fuel costs on this nice, 'clean, environmentally-friendly' E85 ethanol. Now I don't know about you, but it seems to me that the pollution from 225 gallons of diesel is going to be a whole hell of a lot less than the pollution from 1250 gallons of E85.
Obviously this example is extreme, but it does use real-world facts and figures from real-world vehicles you can buy right now. I did it to illustrate how being in posession of the facts can help clear up the doublespeak and misinformation. So if you're considering an E85-fuelled vehicle, you might want to do some more homework first, because it most certainly is not the silver bullet we're all being led to believe.
For more information / propaganda, go to the official E85 fuel site.

LPG / LNG / AutoGas - Liquid Petroleum Gas / Liquid Natural Gas.

In Europe, LPG has been an option for drivers for years. In Australia, it's been around since the 60's. In England, it's still bubbling under and in America it's virtually unheard of. So what is it? Well, put simply, it's petroleum or natural gas compressed to the point where it becomes a liquid. The liquified gas is contained in a pressure vessel inside the car somewhere - normally a tank in the boot (or trunk if you're American). There's a feed line from there to the fuel injection system or carburettor and a solenoid switch connected to a fuel-cutoff switch, both of which are controlled from a button or switch on the dashboard. In one position, the LPG line is closed and the petrol line is open and the car works just like every other car on the road. In the other position, the petrol line is cut off and the LPG line is opened up. Liquid gas under pressure shoots up the line and out of an injector nozzle either screwed into the side of the carburettor, or integrated into the fuel injection system. As the gas expands out of the nozzle it cools down and becomes a gas. The gas is highly combustible and when mixed with the air going into the engine, creates a perfectly useable fuel-air mix for the engine to run on. Simple.
The gas itself is normally some derivative of butane or propane, or a combination of the two. LPG is manufactured during the process or refining crude oil, and LNG is manufactured during the refining process of extracting natural gas from the ground. Once the gas is compressed, it becomes a liquid, and this is what is carried around in the tank in the back of your car.

The pros and cons of LPG

LPG is popular because for the most part, it's cheaper than petrol and it gives a pretty good gas-mileage. There are three key issues that bother most people considering LPG conversions. The first is the tank - it takes up a lot of space in your car. For some this isn't an issue, but for others, they need the space and they don't like the idea of an ugly pressure tank up on the roof of the car. The second issue is availability. On mainland Europe this isn't a problem but in most of the rest of the world, you'd be more likely to win the lottery than just stumble across an LPG filling station. The good news though is that by flicking the switch on the dashboard, you can go back to regular petrol (as long as you've got some in the tank) and keep filling up like that until you do come across another LPG station. The third issue is cost. It costs a fair amount to get an LPG conversion done. LPG is cheaper and in the long run you'll recover the costs and start saving money, but that can take 50,000km or more. Another issue which some people don't like is the idea of the pressurisation system. To fill up an LPG tank, you need to hook on a pressurised hose to a special filler cap on the outside of the car. It's easy enough to do, and it holds itself in place whilst you're refuelling, but for some, they just don't like it. The tank itself will normally be fitted with an automatic fill limiter which looks a lot like a toilet bowl float. When the tank is nearly full, the float operates a lever which severely restricts the flow of gas into the tank. This causes enough backpressure for the pump to realise that it's time to cut off the flow.

Hydrogen.

Hydrogen has been touted as the Next Big Thing in terms of eco-friendly fuels for our cars but the hype surrounding hydrogen is quite a long way removed from the reality. Hydrogen can be used either in internal-combustion form similar to burning petrol, or as a fuel source for a fuel cell which would generate electricity for electric drive motors. In both cases they really don't hold up to scrutiny right now. Future developments will change that but at this point in time, hydrogen is not The Next Big Thing. So why is this?
To start with, hydrogen does not exist as a source of energy without refining. It needs to be extracted from something else in order to be used. This extraction process can be costly and dirty, and in the case of using hydrocarbons as the source, the resulting hydrogen is more polluting than petrol or diesel engines once burned. The more likely method of extracting hydrogen is using water as the source and electrolysis as the method which is both more expensive and slower. Whilst it's true that for the most part the only exhaust from a hydrogen vehicle is water, the problem is that the energy required and pollutants released during the processes describes above are no more appealling than the processes used in refining petrol.
hydrogen BMW The cost of the vehicles is currently prohibitive for all but the developers. Currently all the development vehicles are over $1,000,000 a piece. There are only 20 hydrogen fueled cars in America and even less in Europe and Asia. Arnold Schwarzenegger's Hydrogen Hummer is a one-off $1,200,000 vehicle and isn't representative of anything a consumer could buy. Part of the reason is that to keep hydrogen in liquid form, it needs to be supercooled to -253°C. This means you need either an extremely well-insulated in-vehicle tank, or an in-vehicle chiller to keep the hydrogen at that temperature.
Assuming you could own a hydrogen vehicle, you then face the lack of infrastructure. California's much-touted Hydrogen Highway is a pipedream that'll never happen because of the cost. Even if it did, when you got to the pump, you'd be raped blind for the cost. All that expense in refining, transportation and storage would be passed on to the consumer.
That's assuming you could reach a filling station in the first place. Hydrogen can only be compressed so far and only has so much energy in it. It has a very low volumetric energy especially when compared to petrol. To get a car with a 400 mile range or more (typical for a modern vehicle) you'd need a hydrogen tank bigger than the car itself. The current demonstrator vehicles have hydrogen tanks that fill most of the trunk and a lot of the rear passenger space, and can barely squeeze out 100 miles between fill ups. The GM and Toyota hydrogen demonstrators are always trailered to their demonstrations simply because they would never get there if they were actually driven. The highest range to date from a hydrogen vehicle is BMW's hydrogen demonstrator which managed 240 miles.
The fuel cells for hydrogen-electric cars are another problem yet to be overcome. Whilst they might increase the paltry range further, you need a lot of fuel cells to produce a usable amount of electricity. Stack enough together and they have the equivalent weight of the same number of batteries required to make a pure-electric vehicle but, with the overhead of the pure cost of fuel cells. The fuel cells themselves are expensive to produce and very fragile. They don't take well to bumps and jolts - exactly the environment they're used in when placed in a vehicle, and they require relatively large amounts of relatively rare substances like platinum to make their catalysts.
There's also the issue of storage. Hydrogen molecules are very small and can actually leak through the steel walls of a container - the fuel tank. Kawasaki performed an experiment in Japan where they drove a truck full of cooled hydrogen around and lost about 6% of the payload through leakage. Until a better way is found of storing cooled hydrogen, the leakage problem could be the dealbreaker.
Then there's that whole Hindenburg thing. Sure, the hydrogen didn't cause the fire, but it fueled it. Imagine now crashing in a vehicle with fragile fuel cells, plumbing lines and pressurised tanks full of hydrogen. The manufacturers are keen to point out that their systems are super safe which is a fair comment but what about the 1 in 1000 crash that will happen every now and then if the vehicles are delivered to the public ?

The "Run your car on water" brigade - HHO

You might have come across ads on the web - maybe even ones that Google have fed to this very page - claiming you can buy a kit to make your own car run on water. As a matter of fact you can, and it uses high school physics to do it. It relies on simple electrolysis - the process of using electric current to dissociate water molecules. The resulting gas is oxyhydrogen (sometimes called Brown's Gas or HHO). It's what is used in some cutting torches. With a little fuel-line plumbing and some basic handyman skills, you can fit such a device to any engine, fill the extra tank with water, and be generating hydrogen in no time. The gas is fed into the combustion chamber along with your normal fuel-air mix and for the most part, I believe it will actually give you better gas mileage. However - remember that you use three times the amount of energy to extract hydrogen from water as is contained in the resulting gas. The law of conservation of energy means you're not getting anything for free. In the case of these kits, you're using electricity from the car's battery to generate the hydrogen. A lot of electricity. Enough that it will add increased load on the electrical system, which means more load on the alternator, which means more drag on the engine to turn the alternator, which means a less efficient engine. So what's the net outcome? My guess would be that taking into account the loss of efficiency in the engine due to electrical load, and the increase in efficiency from the hydrogen, you're probably not going to see more than an 8 to 10% increase in economy (the difference in energy contained in the water vs. the car running on petrol alone), if that. I could be wrong though. If you have one of these HHO kits running successfully on your car, I'd like to hear from you.
To quote something I saw on a forum post talking about this sort of thing:
Generating H2 + O from water = easy
Running a car on it = not too hard
Getting more energy out of the H2 + O than you put in to split it = impossible.

The slightly more 'out there' version of running your car on water

No article on water powered cars would be complete without mentioning Stan Meyer or any number of other people who claim to have made cars run on water alone. Stan Meyer's idea was more unique than most - rather than generating hydrogen and storing it to be burned later, he claimed his system was a water splitter that fractured water into hydrogen and oxygen instantaneously to be burned. The water never got hot and he claimed it wasn't pure electrolysis because he was using very low current. He spent a lot of time selling the idea and getting patents for a system of electronics and oscillating radio frequencies coupled to his separation chamber. It sounded too good to be true. When he started telling the press that he'd been offered $1bn by the Arabs to sit on his invention, and that he was getting 1700% more energy out than he was putting in, it looked more and more like those badly-spelled emails from "your friend George" in Nigeria who promises cheap drugs, a giant penis, and more money that you've ever seen as long as you send him $10,000 in cash right now. I believe Meyer was eventually convicted of fraud for all this in 1996 and then died in mysterious circumstances in 1998. Conspiracy theorists will tell you that he was seen off by Big Oil.
The problem is that you have to remember other huge 'scientific breakthroughs' in this area, like like Martin Fleischmann and Stanley Pons claiming to have solved cold fusion. Something else that seemed to be too good to be true and in the end turned out to be just that. I've got to stick to current scientific thinking on this for the time being, that being the law of conservation of energy again. Until someone can publicly demonstrate such a system that anyone can reproduce, and reproduce successfully and frequently, Meyer's water fracture device will remain a myth. That's not to say we shouldn't be open to the fact that science is wrong on this subject. Remember - everything we know is only as right as can be proven today - at one point the earth was flat and the sun revolved around it, and until it was proven otherwise, that was also scientific 'fact'.

The eBay problem

This paragraph may seem a little out of place but I have had a lot of problems with a couple of eBay members (megamanuals and lowhondaprelude) stealing my work, turning it into PDF files and selling it on eBay. Generally, idiots like this do a copy/paste job so they won't notice this paragraph here. If you're reading this and you bought this page anywhere other than from my website at www.carbibles.com, then you have a pirated, copyright-infringing copy. Please send me an email as I am building a case file against the people doing this. Go to www.carbibles.com to see the full site and find my contact details. And now, back to the meat of the subject....

Gas-mileage, mpg and why American cars can never match the EPA estimates.

Gas-mileage is the quickest indicator of how efficient a car is in terms of fuel used for distance driven. Engine size and power, driving conditions, weather (wind especially) and vehicle weight all affect mpg. Measuring gas-mileage is really easy but it's surprising how many people don't know how to do it. Basically, zero your trip counter next time you fill up, then drive as normal. When you fill up again, let the petrol pump fill to the auto-cutoff point and then make a note of the trip meter reading. Gas mileage is the number of miles on your trip meter divided by the number of gallons the petrol pump put into your tank. You'd be surprised the number of people who use the manufacturer figure for the size of the tank in that calculation instead of the amount of petrol actually put in.
In England and Europe, pumps deliver in litres, so in the UK it's miles-per-litre, although most advertising still uses miles per gallon. It's worth noting that an English gallon is 1.2 US gallons. So when you see a car in England that advertises 40mpg, it's the equivalent of 33mpg in the US.
In the rest of Europe it's normally advertised as litres per 100 km. So for example, 28mpg (UK) is about 10litres/100km. Often this is short-handed to 1-in-10, meaning 1 litre used in 10km of driving.

The EPA

The American EPA (Environmental Protection Agency) rates all cars sold in America with gas-mileage figures, advertised as EPA-rated mpg figures on the new car sticker. It's one of the things car manufacturers rely on to sell their vehicle, especially with today's high fuel prices. Not many people understand this, so I'm here to take some of that confusion away and tell you what the EPA figures really mean.
epa sticker First of all, there's the sticker you'll see in every new car in an American showroom, an example of which is seen on the right. There's a load of technical blurb on there to advertise the vehicle, but the two big numbers are the EPA-certified fuel information figures. In this case 20mpg city and 28mpg highway. So you see these figures and you get into your head a rough idea of how often you'll be filling up. The problem is that these are very rough estimates. If you read the small print, it says this:
"Actual mileage will vary with options, driving conditions, driving habits and vehicle condition. Results reported to EPA indicate that the majority of vehicle with these estimates will achieve between 17 and 23mpg in the city and between 23 and 33mpg on the highway."
Okay so it's pretty obvious that driving habits, conditions and vehicle options (like a bloody big roof rack) will affect your mpg, but what's less obvious is the "between" figures. It's basically a get-out clause. In this example, the vehicle is more likely to get 17mpg in the city and 23mpg on the motorway - the low end of the "between" figures.
In the 1980s, the EPA conducted a study on their results vs. the real world, and discovered most drivers got significantly lower mpg figures than the EPA predicted. As a result, EPA estimates on the new car labels were dropped by 10% for city and 22% for highway from their actual results. In 2006 they dropped another 8% from those figures again to try to make the numbers match more closely.
Even that isn't the end of the story though. What you really need to know is how the EPA come up with the figures in the first place. Before you carry on, you might want to put down any drinks or breakables because I know what your reaction will be at the end of this. Ready?
Congress and car company lobbyists require the EPA to measure mpg figures using the following simulated real world conditions in a lab. That's right - EPA testing happens on a dyno in a lab, not on the open road.

Average highway speed : 49mph
Maximum highway speed : 60mph
Temperature : 75°F
No rapid acceleration
No air conditioning
No passengers
No rough roads
No hills
No wind
No low tyre pressures
No ethanol in gas

Well the first problem is the last point : no ethanol in gas. In America, you can't buy zero-ethanol petrol - it's all E-10 (see above) so you're already going to be down 5% on the EPA figures even if you could meet all the other requirements. And for the love of God, who drives like this? 49mph on the motorway? Maximum speed 60mph? Perhaps when the model-T Ford was the Big Thing, these were valid speeds, but nowadays (and by 'nowadays' I mean 'in the last 6 decades') motorway speeds are typically 70mph maxing out at 90mph (if you're in Europe anyway). What about the rest of it - no hills, no passengers, no rough roads? Have the EPA actually driven a vehicle in the real world recently?
As a rough benchmark, driving at 65mph instead of 49mph will decrease mpg by 20%. Driving at 75mph will take another 25% off that. In short, you should pay very little attention to the EPA estimates because they are, for the most part, completely meaningless.
Muddying the waters even further
Remember above I said that the city and highway figures were "between" figures, or the average of the high and low EPA tests? Well I'll give you one guess which figure the car manufacturers use in their print and media advertising. That's right - the high-end of the range. In the example above, the low highway figure was 23mpg and the high was 33mpg. In this case, the advertising will always publicise the 33mpg figure. You will likely get not much more than the low city figure - 17mpg.
Trying to give you a concise answer.
They say a picture speaks a thousand words. I don't have a picture for you but I do have a table. This is a quick reference for you to show all the various figures that go into the EPA estimates, the advertising and what you should expect in the real world. It's based on the Mercedes CLK320 sticker shown above. The blue row shows what you'll see on the EPA sticker in the window of the car. The red shows the figure you'll see on TV and the green row shows what you should expect when you drive this car in the real world.

	City Low	City High	City Avg.	Highway Low	Highway High	Highway Avg.	Combined Avg.
EPA LAB TEST	21.6	26.3	23.9	26.3	42.1	34.2	29
-15% (1980 correction)	18.4	25	21.7	25	35.8	30.4	26
-8% (2006 correction)	17	23	20	23	33	28	25.5
-5% (you're using E-10 petrol)	16.1	21.8	19	21.8	31.3	26.6	25.1
What you should expect	15	20	17.5	20	30	25	21.2

If you're curious about what others are getting in the real world, there's two websites that will help you out:
fueleconomy.gov is the US government's own website where people like you and I contribute to their real-world mileage database.
GreenHybrid.com which is based more on hybrid vehicles, but there are a lot of non-hybrid vehicles in there. My Honda Element is one of them. The following graphic is continuously updated based on my account. Compare my actual mileage to the claimed 21/24 that the EPA advertises for my vehicle. If you're interested in nauseating detail, clicking the graphic will take you to a tank-by-tank breakdown:

So the EPA numbers are essentially useless then?

Yes, apart from for one thing. Too many people try to perpetuate the myth that the EPA values are intended to suggest what a driver could expect to get in the real world. As I've shown in mind-numbing detail above, this is simply not the case. Instead, they are best used as a comparison between one vehicle and another, ie if one vehicle is EPA-rated at 20mpg and another is EPA-rated at 25mpg, then you can pretty safely conclude that the latter gets 25% better mileage than the former, and nothing else. For a good read on this subject see the Patrick Bedard column in the Feb 2006 issue of Car and Driver magazine.

2008 : The EPA adjust their figures.

So you've waded through all this crap about the EPA and how the estimates are pretty much irrelevant, only to come across the above heading. Yes, it's true. The EPA changed the way they measure mpg figures starting in 2008. The big changes are:

The new tests start with the car at 20°F. The old tests started at 75°F. Why the change? A cold vehicle uses more energy than a warm one. Cold temperatures are especially hard on the batteries that power hybrids, so hybrid mpg ratings dropped.
The new tests use a maximum highway speed of 80mph instead of 60mph. At that speed more engine work is done to overcome drag than to actually keep the vehicle moving at speed.
The new test includes hard acceleration. The old test used gentle acceleration. This one also affects hybrids because hard acceleration relies entirely on the regular petrol engine and uses none of the electric hybrid parts.
The new test now assumes air conditioning is used 13% of the time. The old test didn't use air conditioning at all. 13% is the mean average for all major cities across all times of year for the US.

But even with these new standards, the EPA test still takes no account of hills or wind. This has the effect of skewing the test in favour of larger vehicles like SUVs. If hills and wind were included, the results would be radically different - larger, heavier vehicles use more energy to travel into wind and up hills, ie. more fuel. The 2008 EPA estimates would be far more useful if they included these factors. Because they don't the overall fuel consumption figures for SUVs are lower than is realistic.
For example. Assume a car gets 40mpg without the hills and wind test, and 38mpg with. Now imagine an SUV doing the same tests gets 24mpg without the hills and wind, and 19mpg with. For the sake of comparison the car's 40mpg vs. the SUV's 24mpg doesn't look as bad as the car's 38mpg vs. the SUV's 19mpg. But I digress.

So what's the outcome of this? Well first of all, the new figures are closer to what you or I could get from a car. Hybrids still suffer a hit of about 30% loss of mpg for highway and 20% for city. Regular non-hybrids will drop about 12% for highway and 8% for city. It's a lot closer to the real world than it was, but is it close enough or should we still just use the EPA figures as an arbitrary comparison of vehicle mpg as measured against an arbitrary scale? Time will tell, but it could be argued that the major car manufacturers and oil companies lobbied for this change to take the shine off hybrid vehicles - after all, they're the ones that suffer the most with the new rating. If you're curious, here's an example of the 2008 window sticker:

Image credit: EPA

The transatlantic conundrum

Here's a question for you : why do identical cars, made by the same manufacturer, get less mpg in America than they do in Europe? I know a lot of you are reading this now thinking "Aha - that's because an imperial gallon is larger than a US gallon". Yes, but even adjusted for that, it's still true. Take for example the 2008 Honda Civic 1.8 i-VTEC 5-door manual. It's a good example of an average family saloon/sedan car. The trim levels are identical, as are the engine and gearbox, and power and torque figures. Oddly, the European cars weigh more for the same trim level. The following are all converted to US gallons:

	City mpg	Highway mpg	Combined mpg	Peak power	Peak torque	Kerb weight
UK	28	43	36	140hp @ 6300rpm	128lb.ft @ 4300rpm	1281kg
US	26	34	29	140hp @ 6300rpm	128lb.ft @ 4300rpm	1241kg

Another example saloon / sedan car. The 2008 Volvo S40 2.4i. Again - same trim level, engine and gearbox. Once again, the European car weighs more:

	City mpg	Highway mpg	Combined mpg	Peak power	Peak torque	Kerb weight
UK	20	37	28	170hp @ 6000rpm	170lb.ft @ 4400rpm	1481kg
US	20	28	24	168hp @ 6000rpm	170lb.ft @ 4400rpm	1460kg

Doing the test differently

Interestingly, the EU mpg test is done on the road instead of as a lab test so you would expect it to give a worse figure, not a better one because the test isn't skewed in favour of unrealistic scenarios. However, it's obvious when you look at the 2008 EPA testing methodology that they took a leaf out of the EU book. This is how the EU do their mpg tests:

Urban (city) : cold engine, accelerations, steady speeds and decelerations. The average speed is 12mph representative of city commute speeds (very harsh on mpg) and the distance is 2.5 miles.
Extra-Urban (highway) : warm engine, accelerations, steady speeds (50% of the test) and decelerations. Max speed is 75mph, average speed is 39mph, distance is 4.3 miles.

So why the huge difference? The EU regulatory body and the EPA use very similar methods of determining the mpg figure so it's not that. You'd expect the figures to be within a couple of percent of each other, but they're clearly not. In fact with the EU cars weighing more you'd expect their figures to be worse. If you think you know the true answer to this (ie, not Big Oil conspiracy), drop me a line. Suggestions so far:

Different Petrol Octane/Composition: Good idea but the calorific value of low-octane fuel is pretty much the same as high-octane.
European and Japanese cars are designed for higher-octane fuels (higher compression).: Might be true but most European vehicles run Euro95 petrol, which is the equivalent of American (R+M)/2 89 octane. Plus, the engine specs are identical - same compression ratio, same torque, same horsepower.
Different Oil Type/Viscosity used
Different 'Map' on the ECU for different emissions laws
Tyres - different rolling resistance?

For my money, the best one is the different engine map in the ECU for emission laws, although emission laws are stricter in a lot of parts of Europe than they are in the US which you'd think would make the mpg figures worse.

Reader ideas

The Transatlantic Conundrum has generated more buzz on my email than Lindsay Lohan getting out of a limo with no knickers on. Some of the ideas are quite sensible. Some are way out in left field. Scott Brereton emailed me with one of the more intelligible ideas:
Like yourself I suspect that its related to engine maps, and I think it may be a quite subtle effect of differing emissions laws.
After doing some research it turns out that in the UK emissions standards measure carbon monoxide(CO), hydrocarbons(HC) and lambda. Looking at the regulations for the US, as far as I can tell CO, HC and nitrogen oxides(NOx) are measured. Due to differing test methodologies, I can't make a direct comparison between the CO and HC figures, hence why I'm phrasing all this with lots of 'maybe's.
Since NOx is formed under lean combustion conditions, it might be the case that fuel maps in the US are tuned richer than in the UK to minimise NOx production, this will lead to higher CO and HC but if we suppose that the CO and HC standards required in the US are more relaxed then those in the UK this would not be a problem. This richer fuel map might go some way to explaining the differing fuel consumption figures seen on either side of the Atlantic.

Reader Blaine writes: It's based in the US EPA's pre-occupation with NOx levels. Recall that European smog police pay little attention to NOx, and concentrate on HC, CO, and CO2. Also recall that NOx formation occurs at extremely high temps (2700+ degrees?).
US emissions systems use a catalyst to bring down NOx levels. The problem with this catalyst is that it doesn't work at "low" temperatures - even those typically found in exhaust systems. US emissions systems make this catalyst work by dumping raw fuel (or running an exceedingly rich mixture) into the exhaust stream, to burn in this NOx catalyst to keep it hot enough to perform the reduction reaction to eliminate/reduce NOx levels. This results in somewhat excessive fuel consumption, obviously.
Tuners in the US, on OBD-II vehicles, have figured out that eliminating this fuel enrichment can result in a fairly substantial gain in fuel economy, especially when combined with fuel-map and timing tweaks designed to increase fuel economy in other circumstances.
It's the "good-fast-cheap" triangle: "good, fast, cheap; pick two". Automotive engines are governed by a similar triangle: power, economy, emissions. European ECM's can pick two; American ECM's can only pick one, by federal mandate - emissions (every other consideration - power, fuel economy, driveability, etc - comes in as a distant second place). By going to a more european style of ECM mapping, American tuners can work some pretty amazing feats, and still maintaining emissions levels.

Torque and BHP

There are two values that are generally published for an engine which tell you how strong the engine is, and they are torque and bhp - brake horsepower.
Torque is a measure of the twisting power of the engine. Torque is directly related to acceleration; the more torque, the quicker you'll get up to speed. Horsepower is what will keep you at speed once you've accelerated and is directly related to the torque readings. So a high-torque, low-horsepower engine will accelerate well but be unable to maintain a high speed. Similarly, a low-torque, high-horsepower engine will not have much acceleration but will be able to go at a fair clout once it's going.

The difference between horsepower and bhp

In England and the US, horsepower means Imperial horsepower. The technical definition of this is "the power a horse exerts in moving 550 pounds of cargo a distance of one foot in one second." This calculation can include just the horse and its own weight. Horsepower can be defined many ways. One horsepower equals 746 watts, and as such, proper SI units are normally used instead. The term horsepower is more a legacy term than anything else.

The term brake horsepower came about because of an apparatus called a water brake that can be used to measure horsepower. Today all manner of brakes are used from hydraulic to electrical. They all perform the same function though, and that is to load up the engine and measure the torque with strain gauges. BHP figures can be calculated from the measured torque values to determine the power of the engine at any given rotation. If bhp figures are published without any other data, you've got to assume they're measured at the crank. The problem is that once you add on clutches, flywheels, gears, driveshafts and all the other components between the engine and the wheels, the actual power at the wheel is often noticably less. So sometimes you'll see bhp figures noted as "at the wheel". This means the torque has been measured with the wheel being turned through all the above connections to give a more accurate power reading.
In the bad old days, bhp readings would be taken with the engine running in "optimum" condition, ie. with no oil or water pumps attached, direct cold-air injection, super-cooled coolant, no exhaust back pressure or catalytic converters and so on and so forth. Fortunately today there are standards that have to be maintained. Most recently, in 2005 the SAE made some changes to the test procedures to eliminate some of the 'slop' in power measurements, and for car manufacturers to be able to make valid SAE-certified bhp claims, their tests must now be monitored by SAE representatives. The results of this change were interesting if only because the bhp values for engines changed without the engines themselves being modified. For example the Honda Element engine remained exactly the same, but its bhp rating dropped from 170bhp to 165bhp, simply because of the new procedures.
It's worth pointing out that whilst the rest of the world used bhp or kW (kilowatts) to publish power figures for engines, in America they typically used to use hp(SAE) instead, meaning the rated power of the engine as installed in the vehicle, ie including all the engine components, pumps, drivetrain etc. Having said that, even today, all hp(SAE) or SAE-certified bhp figures are taken at the flywheel and thus still don't really tell you how much power is getting to the wheels. The only way to know that is to put your car on a dynomometer (a dyno) and get true at-the-wheel readings.

Calculating horsepower and bhp

The formula to calculate bhp from a given torque reading is as follows:

Pi is obviously 3.14159, the torque value should be in pounds-feet and RPS is revolutions per second - RPM/60. So do a little elementary maths and you can massively simplify the formula down to this:

The formula to calculate regular horsepower from a given torque reading is as follows:

Pi is still 3.14159, but this time the torque value should be in newton-metres. Again, simplified the formula becomes:

"Tuning" your engine - how to get more power

Not satisfied with the power your lump is giving you? There are solutions, and of course they depend almost entirely on how deep your pockets are. Almost any engine in any car can be adjusted, tweaked, modified and tuned to give more power. The more money you have to spend, the quicker your car will go.

Chipping / remapping

superchip About the simplest and easiest modification to most modern engines is called chipping. When it was first introducted, it involved removing the chip that contains the ignition map from the engine management system, and replacing it with one with a modified map. The new chip was designed for better torque, increased power, or just smoothing out flat spots in the power or torque curve of the engine. Nowadays, chipping should be more accurately referred to as Remapping. Gone are the days when you could just a whip a chip out of the ECU. That's so 90's. Today, when you cough up your hard earned cash at a tuner house, they'll plug a laptop in to your engine diagnostics port and upload new software which changes all manner of things from turbo control, fuelling maps, engine load and torque limiters all the way up to throttle-by-wire response (where applicable). They write their own software after studying (read: reverse-engineering) the car's ECU parameters using a rolling road and a laptop hooked to the diagnostics port. From there they can re-write the engine management software to do what they want rather than what the manufacturer wanted. Petrol cars respond well to remapping, but for some reason, diesels respond much better, especially VW diesels. It's not uncommon for a remapped VW ECU to generate 30% more power and torque after it's been breathed on. Add a turbo to that and you can see even wilder gains. Realistically though you ought to expect around a 5-7% increase in horsepower from a chip or remapping operation.
Getting your car remapped will take a couple of hours if you go to a reputable tuner house. They'll pop your steed on a rolling road and hook it up to a dyno to get it right. In some cases, you can get a remapping module which sits in-line with the factory-fitted ECU, and then you can download or create your own mappings and upload them to the unit yourself. Power Commander are one of the more notable manufacturers of this sort of system, although theirs is predominantly designed for motorbikes.
But how can this work? More torque and horsepower without changing anything in the engine? Well bear in mind that from the factory, most cars are sold to be more economy and comfort biased than performance biased. Most engines have a lot of slack for generating more power or torque, it's just a question of having the expertise to find it. A lot of work does go into these chips and remapping programs which is why they can cost upwards of $400 for a quality branded product. Whilst it might only be 5% by the numbers, you likely will notice some of the other effects, like smoother acceleration due to flat-spots in the torque curve being ironed out. Everyone I know who has chipped their vehicles has enjoyed the modification, and relative to what you can do to a car, it's a pretty cheap modification.
Something to be aware of : chipping or remapping your car will likely void any warranty you have on it because you're messing with the onboard computer which in turn is going to adjust the running of the engine to be "different" from factory spec. And by "different", the manufacturer normally means "no warranty". Having said that, some tuner houses have perfected their software to the point where manufacturers own diagnostics computers can't tell that an engine has been remapped. In that case it becomes a moral issue for you - is it invalidating the warranty if they can't tell?

Factory upgrades

mopar srt-4 upgrade Some manufacturers do bolt-on upgrades to their vehicles. For example Dodge introduced a bolt-on upgrade to their SRT-4 Neon in 2003. The kit comes with a modified engine management computer (the whole thing, not just the chip) along with high-flow fuel injectors. The nice thing about doing a factory upgrade is that you know for 100% certain that the parts are going to fit, and are going to work together with each other as well as your car. Since that original upgrade, Mopar have produced a veritable treasure trove of bolt-on upgrades for Dodge vehicles, and with most of them you can maintain some of the factory warranty. Factory upgrades are starting to include chips too now, competing with the aftermarket chipping business. That was a move to counter the warranty problems that some kits caused. Either way, factory bolt-ons are A Good Thing. If you want improved performance but are nervous about third-party products, getting something direct from Dodge, Ford, Toyota, Mazda etc. is a good way to go.

High-flow filters

K&N high-flow air filter Think of your engine as a breathing machine. It needs to breathe in fuel and air, and it needs to breath out exhaust gasses. Anything that gets in the way of that process is going to impede its ability to breathe. In reality of course, there are plenty of things in the way from air filters and flow sensors in the intake system, to catalysers and bizarre kinks and curves in the exhaust system. By eliminating or reducing these constrictions, you can allow your engine to breathe more easily. Sort of like Nyquil or NightNurse for an engine. By far the easiest and cheapest thing to start with is the air filter. From the factory, air filters are designed to be a compromise of filtering the guck out whilst letting the air through. Aftermarket manufacturers such as K&N and Jamex have been making high-flow air filters for years. The design of the filters is slightly different and they allow more air to pass through the filter whilst still stopping the majority of harmful particles. Again, like all these things, the claims of increased power can be hugely exaggerated. In truth, simply changing the air filter will probably add another 2 or 3hp to your engine. More air going in more easily means the engine management system will adjust the fuelling accordingly and you'll get a better fuel-air charge in the cylinder, resulting in a slight increase in power.
Exaggerating the claims. As with most bolt-on performance parts, the box will always be optimistic with their claims of power increase. A reader sent me a link to this YouTube video testing a VW Golf Mk3, 1.8 litre engine with a stock OEM air filter versus a conical high-flow filter. The filter manufacturer makes the claim that their product will increase the power of your engine by 10%. In this particular test, the horsepower went from 91.9hp with the OEM filter up to 93.6hp with the high-flow filter - a difference of 1.7hp or 1.8%. This is basically an inconclusive result given the measurement and fault tolerance of a rolling-road dyno which is normally in the 3%-5% range. It's certainly not the 10% promised on the box and is closer the 2hp-3hp I would expect from such a filter. youtube : High flow air filter test.

Cold Air Induction (CAI) kits

K&N intake kit cold air intake kit Moving on a step from simply changing the filter, you can then start looking at intake upgrade kits, also known as cold air intake or induction kits (manufactured by companies such as Injen and AEM). The basic idea with these is to make the passage from the filter to the engine less convoluted. When air is forced to go around corners, it causes turbulence which slows down the flow. By trying to make the intake pipes smoother and straighter, the idea is to give the air more chance to get to the engine and less chance of being screwed up in corners with turbulence. Cold-air kits normally remove the factory airbox from the car and poke the air intake into one of the front wings or right up front. The air in your engine bay is hot - really hot - and hot air is not conducive to good combustion. By routing the intake to somewhere where it isn't going to be sucking hot air from under the hood, you get cooler air going into your engine. Because cooler air is denser, you can get a better fuel-air charge into the cylinder than you can by simply changing the stock air filter. Cold-air intake kits can add another 3 or 4hp of raw power to the engine but more often than not, you'll notice an increase in torque lower down the rev range too. The photo to the right was snaffled from a tuning forum but it shows a nice example of a cold-air intake kit once fitted.

Throttle body heater bypass

Cold air induction kits work pretty well but you need to do your homework first. A lot of cars have throttle body heaters, whereby coolant from the engine is circulated around the throttle body casing. The idea is to warm up the throttle body to prevent icing in cold weather. The problem is that these systems are hard-wired and don't take account of external air temperature, so even in the heat of summer, hot coolant is routed around the throttle body. This is a problem for CAI kits because you've gone to all the trouble of putting a nice kit in to suck cooler air into the engine, but at the final hurdle it runs through a 75°C throttle body which heats it up again, negating the whole point of the CAI kit in the first place. The solution to this is a throttle body heater bypass, which essentially involves pulling the coolant hoses off either side of the throttle body and patching them together with a length of copper pipe and two hose clamps. When you do this, the throttle body stays at ambient temperature and the CAI kit gets a chance to do its job. The only downside to this is if you live in a cold, humid climate, you might suffer from icing in the winter. But hey - if you do, reconnect the coolant hoses for the winter...

High-flow exhausts

So you've eased the flow of air into the engine, what about the exhaust? Your typical exhaust setup has kinks and bends in it to make it fit the engine compartment and under the car. In some cases these can be smoothed and straightened out somewhat but more often than not, the exhaust has to take the same route as stock. In this case, the best option is for a larger exhaust. Larger diameter exhaust pipes can accommodate more gas flowing through them and hence provide less constriction to the engine when it is blowing out exhaust gasses. Typically a factory exhaust will have two constriction points. There will likely be the catalyser at the front (where the exhaust is hottest and makes the catalyser work best) and a muffler can at the back. High-flow cat-back exhaust systems are so-called because the start at the output of the catalyser and replace all the exhaust from there back. They will have larger diameter pipes and a high-flow muffler at the end. Alternatively you can get header-back exhausts which replace everything from the exhaust header to the back, typically removing the catalyser in the process. These are sometimes affectionately referred to as catless or no-kitty exhausts.
Adding a sports exhaust system like this can add another 4 to 5hp but you need to make sure you get one which is made by a well respected manufacturer with a good warranty. Because of the change in back-pressure, these exhausts can cause erratic engine problems on some cars that rely on a certain amount of back-pressure to operate properly. Note: back-pressure is the natural resistance to gas-flow in a normal exhaust.
The following picture shows an example of a typical factory-fit exhaust on the left versus a high-flow header-back exhaust on the right.

Keying your spark plugs

ignition spark There's a little known method of squeezing some more efficiency out of your engine, known as spark plug keying. The idea is simple - expose the spark to the incoming fuel-air charge. If the grounding strap on the bottom of the spark plug faces the incoming fuel-air charge, the spark is effectively 'shielded' from the mixture. The image on the left shows a Schlieren photo of a spark emanating from a spark plug tip. You can see the area behind the ground strap doesn't have as much exposure to the spark. Now I know a spark is a spark, and any spark in a fuel-air environment is going to make it burn, but if the spark is facing the intake valves, then there's nothing obstructing the mixture from getting at it. In thousandths of a second, this does actually make a difference to your burn efficiency.
The problem is that when you screw a spark plug into your cylinder head, you have no idea which way the electrode gap is pointing. For best efficiency, it needs to be facing the intake valves or ports as I mentioned above. The solution is pretty simple. Before you install the spark plug, use a marker pen to put a mark on the insulator that aligns with the electrode gap at the bottom of the plug. It's important to use a marker pen and not a pencil because pencil lead is graphite, which conducts electricity. You don't want graphite on the outside of your spark plug conductor!
tip Once the plug is marked, screw it into the cylinder head remembering that you'll need a quarter turn to snug it up. If the mark on the insulator is a quarter turn from facing the intake valves when the spark plug is finger-tight, you'll know once it's snugged down that the gap will be facing the intake valves inside the combustion chamber.
If the mark isn't in the right place, don't go over tightening the spark plug to force it into position! You can get keying kits which are basically replacement crush washers that are slightly thicker or thinner than the standard one. They come in one-third, one-quarter and one-half sizes, meaning that they can affect how far you can screw the spark plug in by the matching amount. So if you finger-tighten the spark plug and the mark on the insulator is facing totally the wrong way, once it's snugged down it will still be a quarter turn away from the intake valves. By changing the crush washer to a quarter-turn crush washer, you'll be able to get an extra quarter turn before the spark plug is tight, which will solve your problem and the electrode gap will now be facing the right way.

Gas-flowed or polished cylinder heads

If you've changed your intake system and your exhaust system, there is one other place full of nooks and crannies where intake charges and exhaust gasses can get discombobulated, and that is the internal passageways in the cylinder head (shown in red in the picture here). Most heads are cast from dies, a process where molten metal is poured into a sand or ceramic die to create the required shapes. Small bits of swarf and casting anomalies are normally dealt with where they are visible but it is possible that the airways in the head still have some rough surfaces. Gas-flowing a cylinder head involves taking it off the car and refining those airways with one of two methods. The cheaper and more basic method involves manual polishing using different grades of sanding and polishing tools. These are manually run around the passages, smoothing off rough edges and polishing the airways to a chrome-like finish. The more expensive method involves hooking the cylinder head up to a machine which pumps superheated plasma through the airways, which literally melts a thin layer of them off based on the actual flow of the plasma itself (which mimics airflow). Both methods achieve the same results - teflon-smooth air passages for the intake charge and exhaust gasses. Getting gas-flowed heads can add another 11 to 12hp to the engine, plus if you want to put a large-bore exhaust on the car, then the gas flow method can widen the exhaust ports to match.
Rough or smooth? There's an ongoing debate about whether or not polished intakes actually are the best thing for airflow. Some people go with the 'smooth is best' whilst some reckon that a rough intake is better. Chroming or polishing the intakes gives a smooth surface which impedes the airflow less, whilst the rough surface generates turbulent surface 'bubbles' which move slowly, but allow the air on top to skip over them quickly. The point of polished intakes isn't so much to give a smooth surface to the actual intake as it is to make sure there are no kinks, metal seams or casting burrs that will act as a restriction to the airflow.

High-lift or lightweight cams

You can squeeze even more power out of your lump if you change the cam or cams at the top of the engine. Lightweight cams weigh less (duh!) and so impose less mechanical drag on the internal parts of the engine. Less weight and less drag mean less power lost to friction and driving the cams themselves. High-lift cams take a slightly different approach. If you look at the 4 stroke diagram way back at the top of the page, you'll see the lobes on the cams are what force the valves to open. The lobes on a normal cam are egg-shaped. On a high-lift cam, they are more rounded-rectangular shapes. The result is that as the lobe spins round, it begins to open the valve sooner, keeps it open longer and then closes it later. The principal is simple : if the valve is open longer, the engine can suck more fuel-air mix in before the combustion cycle. The picture below shows an (exaggerated) example of high-lift cams. The camshaft on the right shows a regular lobe shape and the one on the left shows how a high-lift lobe might look. The difference is subtle but the one on the left would result in the valve opening sooner, staying open longer and closing later.

If I'm starting to sound like a scratched record, then you've noticed the overriding theme of getting more power - getting more fuel-air mix into your cylinders by any method possible. As they say on naff informercials But wait - there's more! Let the scratched record continue......

Even more power

Water injection cooling

As weird as this sounds, you can actually make most engines perform better in some circumstances by injecting water directly into the fuel-air mixture. It sounds counterintuitive but the principal is really simple. Vapourising water into the fuel-air mix will cause the air to become denser and cooler. Cool, dense air results in a better charge into the cylinder head, which results in a more powerful burn during combustion. This naturally results in more power. Water injection is used on WRC (World Rally Championship) cars but is detrimental to power when the charge air temperature is below 42°C and boost pressure is below 0.6BAR. Because of this a triggering / shut off system is used on some WRC cars that triggers on at 42°C and shuts back off at 38°C, only triggering when boost is above 0.6BAR.

Intercooling

Intercooling takes a slightly different poke at the "cooling the fuel-air mix" equation. Intercoolers are normally found on turbo engines and are designed so that atmospheric air flowing around the outside of them cools the air charge from the turbo inside them. The cooler air for the outside can be direct- or indirect-flow. Direct flow designs have the intercooler mounted at the front of the car in the airflow. Indirect-flow units are mounted somewhere in the engine bay with hoses and scoops to get the air to them.

Water-assisted intercooling

An enhancement to standard intercooling is water-assisted intercooling as found on the Subaru WRX STi. Rather than using water injection into the fuel-air charge, it has an intercooler water spray system that sprays water onto the outside of the intercooler to improve the efficiency of the charge air cooling. The auto version found on the top spec models is ECU-controlled to give 5 second bursts of cooling water when boost is high enough to warrant it. The lower spec versions have a manual switch on the dash that triggers a 5 second burst every time you press the button.

Charge cooling

Charge coolers are a more sophisticated derivative of water-assisted intercooling. Rather than just spraying water around the outside of the intercooler, they have a water jacket around the core with an external water pump and independent radiator. The pump constantly circulates water through the chargecooler jacket and then out to the radiator, keeping the whole unit cool. Chargecoolers work well until the engine starts being more demanding about power - once they get to a certain point, they're overwhelmed by the amount of air being drawn into the engine.

Refrigerated intercooling / chargecooling

Rather than injecting water directly into the air flow, or cooling the body of the chargecooler or intercooler, refrigerated systems force the incoming air over a radiator-like device to cool the air. This heat exchanger is filled with a compressed-gas based and works just like your refrigerator at home. The gas is compressed into a liquid then piped into the heat exchanger. As it turns back into gas, it cools down and hence cools the air flowing over the heat exchanger. The now-gaseous coolant is re-compressed outside the intercooler where it gives off the heat via a secondary radiator positioned in the airflow.

Nitrous Oxide - NoS

Anyone in the street racing scene, or anyone who saw The Fast and the furious will be familiar with nitrous oxide (N₂O), also known by one of the trademarks NoS (Nitrous Oxide Systems - a division of Holley). NoS takes the idea of cooling the inlet charge to extremes. These systems involve an injector unit in the intake system connected via a solenoid release valve to a tank of compressed NoS somewhere else in the car - usually in the boot or trunk. When you push the 'boost' button, the solenoid opens and liquid NoS rushes to the injector. As it vapourises into a gas, it absorbs a phenomenal amount of heat, resulting in a supercooled airflow. At the same time, because it absorbs heat, it splits into oxygen and nitrogen. The normal oxygen content of air is around 20%. With NoS that is pushed up to about 33%. Adding that much oxygen to the intake means you need to also add more fuel otherwise the fuel-air ratio is way off so all NoS kits come with a fuel solenoid and injector too. When you apply the boost, NoS and fuel are forced into a y-nozzle in the airflow just in front of the throttle body. As well as all that plumbing, NoS kits can be enhanced with blow-off valves. If you're sitting at the lights on a drag strip with the NoS system pressurised, it will slowly be evaporating in the system and gaseous NoS is nowhere near as dense as the liquid, compressed form. To get the gaseous stuff out of the line, the blow-off valve is opened by a manual switch in the car to let it out and keep the lines full of liquid NoS. So now you have a highly oxygenated fuel-air mix which is supercooled and thus super dense, being blown into the combustion chamber under pressure, thus forcing more of it in there. The resulting burn is so highly potent that you can easily see a 50hp increase in instantaneous power coming from the engine. Easily.
There are however three obvious downsides. The first is that if your boost pressure is too high, you get way too much NoS into the system and the resulting fuel-air mix can burn so violently that it will blow out your head gaskets and/or melt something important inside the engine. You can safely assume about 20hp increase in power per cylinder before you need to start upgrading to racing parts. The second downside is that the very sudden increase in power from the engine can destroy a non-racing clutch, or if you have a racing clutch, it can torque the drive wheels so much that your tyres simply can't grip and more and you start to skid - not good at speed. The third is that the boost is finite. Once your NoS tank is empty, that's it, no more go-go juice. This is why it's typically only used in street or drag racing because the increase in power is very steep, but very short.
One last thing: however photogenic the neon purple and green gas was coming from the exhausts in The Fast and the furious, that was just Hollywood eye-candy. Your NoS system will not do that.

An Alternative to more power : less weight

Power-to-weight rato

A lot of people think only about power. They want more and more power but they overlook one thing. The speed and acceleration of your car is directly related to the power-to-weight ratio. This is a measure of how powerful your engine is compared to the weight of the vehicle. So a massive V8 lump in a beefy 60's American muscle car might seem like a good idea, but it might easily be outrun by a highly-tuned 2 litre 4-cylinder engine in a super lightweight Japanese car. The actual units of power-to-weight ratio don't really matter, as long as you use the same units when comparing any two vehicles. So you can't use bhp and weight in kilos to measure one vehicle and hp and weight in pounds for the other. So to illustrate power-to-weight ratio, consider the following example. Subaru do several vehicles in their Impreza lineup. From their 2007 range:

Impreza 2.5i 173hp, 3067 lbs kerb weight
Impreza WRX 224hp, 3296 lbs kerb weight
Impreza WRX STi 293hp, 3351 lbs kerb weight

(Kerb weight is the total weight of a vehicle with standard equipment, all necessary operating consumables (such as motor oil and coolant), a full tank of fuel).
You can see as you go up the range, the weight of the vehicles increases, but so does the horsepower. Power-to-weight ratio is a two-sided equation. A vehicle will go faster with less weight, or or more or a combination of the two. With the Subaru example, the power-to-weight ratios look like this:

Impreza 2.5i = 1:17.72
Impreza WRX = 1:14.71
Impreza WRX STi = 1:11.43

The figures are easy to come by - divide the weight by the power to get the ratio. You can see that despite the higher-end cars getting heavier, the increase in engine power brings the power-to-weight ratio down so the car becomes quicker. This explains why motorbikes are so quick compared to cars. For example if you compare the 2007 Honda CBR600RR to the 2007 Subaru WRX STi, it becomes readily apparent why the bike will win every time:

Impreza WRX STi = 293hp, 3351 lbs kerb weight = 1:11.43 power-to-weight ratio
CBR600RR = 118hp, 345 lbs kerb weight = 1:2.93 power-to-weight ratio

So it's not that the bike is more powerful - it's not. The engine is only 600cc and it produces almost a third the horsepower of the car. But the bike weighs so much less that the weight side of the equation drops to the point where the ratio plummets.

Weight is everything

So in a car, weight is everything. It can be expensive to start beefing up the engine to give you more power, but it can be really cheap to reduce the weight. As a rough guide, for every 100lbs (45kg) of weight you remove from the average car, you will drop 1/10 second from a timed quarter mile. For the ultimate sports car or street racer, beef up the engine and reduce the weight; increase the power side of the equation and decrease the weight side of the equation and the power-to-weight ratio becomes more favourable.
So how do you reduce the weight of your car. Well again it depends on how far you want to go. If you don't care about carrying passengers, toss out the rear and passenger seats. Don't mind getting a flat and calling a tow-truck? Get rid of the spare tyre and jack. If you're going for a true drag-strip car, take out the glass windows and replace them with plastic ones. Remove the dashboard, carpet, headliner, etc.etc.etc. Beginning to get the idea? There's really no limit to how far you can go. One of the most popular weight-saving mods is a carbon fibre hood. If you're interested enough in this topic to have reached this point on the page, then you'll likely have seen cars with carbon hoods - they're very obvious because the hood is almost always black.

But why this particular item? Well, the hood of your car provides no structural strength, and it has no crash-absorbing properties in a front-end wreck. It's basically an engine cover. Swapping your factory hood for a carbon fibre one can save something like 4kg (8.8lbs) of weight. Doesn't sound like much? Put 4 bags of sugar in a plastic bag and hold it out at arm's length. That's 4 kilos.
People really underestimate the value of weight in a car. It's why race cars are made of sheet aluminium and carbon fibre. It's why they don't have passenger seats. If you're serious about racing your car, shedding weight every bit is as good as adding power. Swap steel wheels for alloys - less unsprung weight and they look better. Swap steel brake discs for carbon-fibre reinforced ceramic ones (standard equipment on some Porsches) and save weight there. Or if you're totally loaded with cash and don't know what to do with it, get pure carbon-carbon discs instead for even more weight saving. Although if you do that, you'll need a healthy disposable income. Carbon-ceramic and carbon-carbon brake rotors do wear annoyingly quickly but you absolutely will stop on a dime.

A second alternative to more power : less load on the engine

In an ideal world, the engine in your car would do one thing - propel you forward. In real life of course it's doing a lot more than that. It's driving the alternator to charge your battery and in most cars now, it's also driving the air conditioning compressor (when active). Both of these items increase the load on the engine. As a rough guide, every 25amps of load on the alternator equals 1hp of load on the engine, whilst running the a/c can typically sap 5% of the engine's power. Automobile blog dyno'd a BMW Z4 with the a/c on and off and registered 232hp / 212lb-ft torque with the a/c off and 221hp / 204lb-ft of torque with the a/c on - quite a drop.
So imagine you have a 150hp engine in a vehicle in the summer with the a/c on, running the radio and the seatback DVD player and LCDs for the ankle-biters. You're dropping a couple of horsepower for the electronics in the vehicle (electric power steering, power seats, radio, LT circuit, lights etc) and 7½hp because you're running the air conditioner. Your 150hp engine is now performing like a 140hp engine - you've lost a lot of power there. But what can you do? Well the most obvious thing is turn off the a/c. Unless it's genuinely hot outside, don't use it. For example, in the winter, when you're defrosting the windows on a cold morning - don't turn the a/c on - leave it off. Ok the air won't be so dry but you'll also not be sapping that power from your engine. After that you can look at separate charging and battery circuits for things like the radio or ICE install that only load the engine when they need to charge. Upgrade your alternator to a super lightweight item with professional grade ballbearings on the alternator shaft; this makes the alternator easier to turn and induces less drag on the alternator belt (fractionally).
Grounding kits You could also look at grounding kits although the jury is still out on whether these actually work or not (see one in the section at the bottom of this page). The idea with a grounding kit is that you beef up the ground straps in your vehicle to ensure an uninterrupted current flow with less resistance. I'm honestly not sure that this would produce a measurable decrease in load on the alternator but you'll find a lot of these kits being flogged on e-bay. The one thing grounding kits are good for are sorting out the electrics on older cars. For some reason the Mazda RX-7 always seems to benefit from revamping the grounding straps. Bear in mind this isn't going to magically increase the performance of your vehicle though - on an older vehicle you're simply making the electrical system closer to how it was when the car was new.

Turbos and superchargers

Most people know that a turbo or supercharged engine is more powerful, but do you know why? In simple, sexual innuendo terms, they give more suck before the squeeze, bang and blow of your engine. The basic idea behind both devices is a turbine that sits in the intake airflow. As it spins, it physically sucks more air in than the normal induction of the engine and compresses it further down the line resulting once again in more air in the intake charge, which means better burn which means more power. Both devices are known by the common description of forced induction systems. The difference is the way the two devices are driven.

Turbos

First built in 1925 by Swiss engineer Alfred Buchi, a turbo is normally driven from the exhaust gasses. The faster the exhaust gas passes through one side of the turbo, the faster the exhaust turbine spins and the more air it can force in to the engine using the intake turbine on the other side. This is the source of "turbo lag". When you put your foot down, the engine spools up and produces more exhaust pressure, which spins the turbo and accelerates the incoming air. The lag is the time between putting your foot down and the exhaust gasses getting up enough pressure to make a difference. The advantage of a turbo over a supercharger is that the turbo essentially runs on "waste product". The exhaust leaves the car anyway, so why not make use of it on the way out? A turbo can spin up to 150,000rpm and because it's in the exhaust flow, can reach 800°C in some cases.
The picture here shows a cutaway of a typical turbo. The exhaust gasses flow through the brown section at the back, passing over the blades of the centrifugal turbine and turning the shaft connected to the centrifugal intake compressor in the silver section at the front.

Anti-lag systems

As I mentioned above, turbo lag is an omnipresent problem. Anti-lag systems help to minimise this by keeping a turbo spinning whilst the throttle is closed - a condition which would normally make the turbo spool down. Anti-lag works by bleeding a little air past the throttle and dumping unburned fuel into the turbine housing to keep it spinning. When the power is required, the initial spool-up is already done and the turbo can provide power more quickly, with reduced lag. ALS can add over 200°C to the temperature of the turbo forcing it up over 1000°C.

Dump valves

Most turbo cars have dump valves in the intake system. This is a spring-loaded pressure-release valve. Because of turbo lag, you can take your foot off the accelerator intending to slow down, but the turbo can still be spooling up because of the lag. When this happens, the pressure in the intake manifold rises rapidly because the turbo is now trying to jam more air into the engine than it can handle. When the pressure gets to a certain point, the dump valve pops open and relieves the pressure. It's what gives that satisfying "pffssshhhhhhh" sound when you rev a turbo engine with the car standing still.

Superchargers

twin screw supercharger Superchargers work slightly differently in that they're normally driven directly from the crank either via a belt or via direct connection to one of the camshafts. With a supercharger, there is little or no lag because you don't have to wait for the exhaust pressure to build up. As soon as the engine starts to spin faster, the supercharger spins faster because of the direct mechanical connection. That advantage is also a disadvantage. Unlike the turbo, a supercharger is imposing a mechanical load on the engine itself, so a percentage of the increase in power is actually taken up simply in driving the supercharger itself. Modern superchargers are quite compact and can sit either on top of, or next to the cylinder head. The most common type, called a twin-screw supercharger, uses a pair of interlocking Archimedes screw compressors (shown on the right) that suck air in and compress it at the same time. Centrifugal superchargers are almost a hybrid between turbos and twin-screw superchargers. They're still driven via a direct mechanical connection, but rather than having the two screws that mesh together, they have a single centrifugal compressor that looks like the intake turbine in a turbo (above). "Classic" superchargers are what you see poking out of the hoods of souped-up 70s Americana with huge air scoops and giant belt-driven compressors. The picture to the left shows a top-mounted belt-driven supercharger.

Exhaust wrap

This little section almost needs to be considered along with turbos, above, because the two typically go hand-in-hand. When gas gets hot, it gets less dense. Less dense means less resistance to flow. It figures, then, that people who are looking at every tiny minutae of performance would want to wrap their exhaust headers. Why? Well exhaust gas exits the combustion chamber extremely hot (duh!) but it cools rapidly as it travels through the exhaust system. In doing so, two things happen. First, the gas becomes more dense and begins to resist flow, and second, as it does this, it disperses heat into the metal exhaust pipes, which in turn radiate the heat into the engine bay, raising the under-hood temperatures. The problem with the gas cooling down is obvious - it begins to slow down and provide resistance in the exhaust system. The problem with the under-hood temperatures going up is that it makes it more difficult for the engine to get a good, cold charge of air. (Colder air is more dense, which means better, more powerful combustion.) This is why you sometimes see vented hoods on cars; they're designed to let the hot air out and keep the under-hood temperatures down. So wrapping the exhaust headers with exhaust wrap helps because it basically insulates the metal exhaust pipes. This means they retain the heat better which in turn means the exhaust gas remains less dense and keeps up it's high flow rate. For turbos, this is a good thing because it means the exhaust reaching the turbo is travelling faster, which means the turbo spins faster, which means more air forced into the engine. Everything is connected, you see? So the ideal system would be a turbo, with wrapped exhaust headers, a vented hood, a cold-air unduction and an intercooler. That combination, whilst expensive, will give the coldest (and thus densest) fuel-air charge into the engine, whilst insulating the exhaust and ventilating the engine bay at the same time.
It's worth pointing out that not all exhaust wraps are made equal. If the wrap insulates too well, then the exhaust pipes get too hot and that can cause all it's own problems from engine bay fires to structural failure of the exhaust or turbo.
Point to note: It's only a rumour that exhaust wrap absorbs water and can encourage your mild steel headers to crumble away prematurely. If anyone tells you this, they're fearmongering.

Page 1

Page 2

Page 3