Fuel's paradise

The high performance juice that shifts F1 cars is still basically the same stuff you put in your VW Polo, says Michael Scarlett

Today's Formula 1 cars are powered by what is in many ways the most highly developed of all forms of petrol engine. Compared to a good 3-litre production car engine, an F1 motor produces around four times as much horsepower.

Today's Formula 1 cars are powered by what is in many ways the most highly developed of all forms of petrol engine. Compared to a good 3-litre production car engine, an F1 motor produces around four times as much horsepower.

Remembering that power is defined as how fast work is done, one of the reasons why F1 engines develop such power is that they run three times faster in engine speed. The 3-litre unsupercharged engine of a BMW 330i is good for 228 James Watt horsepower (228 bhp) when its crankshaft is whirling round 5,900 times a minute (5,900 rpm). The same size engine of a Grand Prix car turns out approaching 900 bhp at 18,000 rpm.

At 5,900 rpm, the petrol-air mixture has roughly one hundredth of a second to ignite and expand in the power-producing stroke of the four-stroke cycle. At 18,000 rpm, it has three-thousandths of a second to do the same. So you might think that the racers have to use some pretty fancy brews in their tanks.

Even the petrol you buy for your car is a cocktail of different chemicals. Fuel for racing engines was once extremely specialised, but today's Grand Prix engines have to run on what the FIA (Fédération Internationale de l'Automobile), who set the F.1 rules, say is "not far removed from that used in regular road cars." The regulations are "intended to ensure the use of fuels which are predominantly composed of compounds normally found in commercial fuels, and to prohibit the use of specific power-boosting chemical compounds".

The rules specify how much of what chemicals are permitted. To summarise just two main points of a deeply technical list, the petrol can be up to 102 RM octane in its anti-knock rating (standard unleaded is 95 RM, super-unleaded 98 RM), and it has to be what is loosely called unleaded.

Two five-litre fuel samples of whatever is brewed up for any Grand Prix car before the race must be provided for the FIA for analysis and approval. And the FIA can then take more samples during the event to "ensure there is no discrepancy between the fuel being used and that previously supplied in the samples" - in plainer English, that there is no fiddling of the formula.

You might also assume that the engine designer's sole object is to make the engine produce as much power as possible. As the great engineer Ferdinand Porsche is reputed to have said, "The perfect racing car is one designed to cross the finish line in first place, which then falls to pieces." That was not far off what used to happen.

Recently, in an effort to reduce the huge cost of building racing cars, the FIA's regulations require that the same engine must be used for all practice and qualifying laps as well as the race distance. No team may replace the engine used for qualifying with a brand new engine for the race. Next season, each engine has to "do" qualifying and racing distances of two entire events, totalling 1,500 km (over 900 miles). So F1 engines these days are designed to be reliable.

Secondly, although there is no maximum tank capacity regulation, the amount of fuel a Formula 1 car may carry is limited by rules about where fuel may be stored. In any case, as a spokesman for the Jordan F1 team said, "No team could afford to store the 200kg of fuel needed to run a whole Grand Prix race non stop, because the weight penalty would slow the car too much." Hence pit stops for refuelling.

The less fuel a Grand Prix car carries, the faster it will accelerate, which can be useful to help a car in the right hands to lead from the start, and build an increasing gap between it and its rivals. But if too little fuel is carried, and used up too quickly, that car will lose its lead in an early pit stop. So today's F1 car has to also be designed to be, of all things most contrary to motor racing, economical.

"Economical," when extracting circa 900 bhp from a 3-litre engine driven most of the time, flat-out, at a racing fuel consumption of around 4 mpg, is a somewhat relative term. When the composition of the fuel is tightly limited, prohibiting the addition of any substance capable of increasing the fuel's energy content, engineers have to look elsewhere for any efficiency improvement.

As Mike Evans, chemist in charge of Shell's Formula 1 fuel development programme working with F1 World Champion manufacturers Ferrari says, "The teams are really working hard on fuel economy - it is actually a big area. They want to go as far as possible in the race on the amount of fuel they have on board, before they have to stop to refuel. The more economical it is, the less fuel has to be carried, so the less heavy the car becomes. A lot of work on the engine, reducing internal friction, coatings on rubbing surfaces and so on, is all about improving efficiency."

The fuel men can help however. "You want the fuel going into the inlet ports of the engine to vaporise as quickly as possible, you don't want droplets of liquid fuel entering the combustion chamber." In a road car engine, one popular way that any liquid as opposed to vaporised fuel entering the combustion chamber is helped to vaporise is by inducing "swirl" in the chamber - literally stirring the air-fuel mixture as violently as possible, as in cooking.

An F1 racing engine is designed with a very wide cylinder so that as many as five of the largest-possible valves can be fitted in. At the same time, it is made to compress the mixture into as small a volume as possible, for better efficiency. The smallness and narrowness of that space, and the very much more limited time to burn it properly, prevents swirl effects to be used. Therefore as Mike Evans explains, "We can assist by optimising the rate of fuel ignition and expansion by playing around with the evaporative ability of the fuel, its volatility, within the regulations."

He and his team in fact are involved closely with the Ferrari engine designers, right from the start of the design task. In spite of the restrictions of the rules, using the chemical equivalent of the computer-aided design and predictive analysis of modern mechanical engineering, the fuel composition is "designed" simultaneously with that of the engine design - "something never dreamt of in the earlier days."