Formula One Trend of Design

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Forced Induction

A development that has been slow in getting under way in Formula One is that of forced induction. Up to 1950 anyone who was really serious about Grand Prix racing built engines with forced induction, the basic system used almost universally being that of the positively-driven supercharger. Until 1938 it was accepted that all right-minded designers of racing engines would force the fuel/air mixture into the cylinders with some form of pump so there was no provision in Grand Prix rules for differentiating between supercharged engines and those that relied on atmospheric pressure to get the fuel/air mixture into the cylinders. The Grand Prix formula for 1938-40 (they lasted three years in those days) made arrangements to equate supercharged and unsupercharged engines, but the French were the only ones to show interest in the unsupercharged variant. It was considered that an engine of 4 1/2-litres unsupercharged should be capable of producing equivalent power to 3-litres with supercharging. At the time this decision was made multi-stage supercharging had not been developed and a single supercharger had a natural limit of around 20 p.s.i. boost. By combining two superchargers in series it became possible to increase this figure considerably, and thus increase the engine’s power output, even though a compromise had to be made on the overall size of the supercharger layout relative to the power needed to drive the installation. For the unsupercharged engine it was “no contest”, they could not match the power output of the supercharged 3-litres.

After the cessation of racing from 1940 to 1945 activity restarted with whatever machinery was available and because Germany (Mercedes-Benz and Auto Union) had been knocked out of the running this left supercharged 1 1/2-litre “voiturette” cars from Britain and Italy and unsupercharged 4 1/2-litre cars from France. The Grand Prix formula drawn up for 1947 equated these two engine limitations and it seemed reasonable at the time. However, development in the unsupercharged field was very limited and the supercharged 1 1/2-litre cars dominated the scene, the straight-eight-cylinder Alfa Romeo being particularly successful. By 1950 Enzo Ferrari’s new firm was becoming very strong and under the leadership of Aurelio Lampredi a programme of unsupercharged engines was instituted. At the time the Alfa Romeo design was at the end of its development, some 380-400 b.h.p. being wrung out of the 1 1/2-litres. The Ferrari 4 1/2-litre V12-cylinder engine programme was meteoric and 400 b.h.p. was soon forthcoming and the Alfa Romeo had met its match. By 1951, to all intents and purposes, a racing engine of supercharged 1 1/2-litres was the equivalent to unsupercharged 4 1/2-litres.

This happy state of affairs did not last long, as Alfa Romeo withdrew and there was no-one to challenge Ferrari, so Grand Prix racing was for Formula 2 in 1952 and 1953. This category limited engines to 2-litres and superchargers were forbidden, the aim being to control the cost of racing. A new Grand Prix formula was drawn up for 1954-57 and this equated unsupercharged engines of 2 1/2-litres with supercharged engines of 3/4-litre, or 750 c.c. By this time great strides had been made with atmospheric induction and carburetters, fuel injection and gas-flow, both in and out of the engine, had received a lot of development, while the supercharger and forced induction generally had stagnated since 1951. Consequently there was no encouragement for anyone to follow the supercharged 750 c.c. route. This formula was extended through 1958, 1959 and 1960, by which time all thoughts of supercharged racing engines were long forgotten, so much so that the new formula for 1961-65 did not even encompass the supercharger. In 1940 a new Formula came into being, with unsupercharged engines permitted up to 3-litres and supercharged 1½-litres were considered to be the equivalent. The unsupercharged route was now so firmly trodden that no-one gave a thought to supercharged 1 1/2-litres and all sorts of technicians and engine designers proved in theory that a supercharged 1 1/2-litre engine could not hope to match an unsupercharged 3-litre, such was the state of the art of atmospheric induction. With 400 b.h.p. available from 3-litres without the aid of forced induction, it seemed that the supercharger was indeed dead and buried.

Outside in the industrial world, where there were no formulae or rules, engine designers were working on a compressor driven by the exhaust gases, to provide forced induction (of air) for diesel engines, principally in the search for greater torque rather than greater power, and also to improve thermal efficiency with an eye to economy. The process of using exhaust gases to revolve a turbine, with an air compressor on the other end of the turbine rotor shaft, became known as turbo-charging and with fuel-injection available it was not difficult to adapt the diesel-engine’s turbo-charger to a petrol engine. [I first saw an exhaust-driven turbine/compressor unit in about 1942 on a Pratt & Whitney radial aero engine. The Flying Fortress had four of them, two under each wing, each unit feeding its own engine with high pressure air.]

While Grand Prix racing was hide-bound with the unsupercharged 3-litre engine, almost every other form of motoring competition was experimenting with turbo-charging. Drag racing never did lose interest in the conventional supercharger and high supercharger pressures were the normal thing. The turbo-charger over in American Indianapolis and similar racing, in Can-Am racing and in long-distance endurance racing. While the world of Grand Prix were exploring the aero-dynamic field almost to the exclusion of engine development, Porsche, Renault, Lancia, BMW and Cosworth were pressing on with turbo-charging and searching for more and more horsepower for use in competition other than Formula One. Eventually Renault turned their attention to Grand Prix and Formula One with their turbo-charged 1 1/2-litre V6-cylinder power unit. At first the “establishment” (especially those stuck with the Cosworth 3-litre and with no engine development facilities) laughed at Renault’s suggestion the they could match the power output of an unsupercharged 3-litre engine with a 1 1/2-litre, no matter how much forced induction was applied. When, two years later, Renault consistently produced more b.h.p. from their turbo-charged l½-litre than any 3-litre engine there were cries of “unfair”.

In the development of 520 b.h.p. from 1 1/2-litres there were two major steps that Renault made. One was “inter-cooling” of the air charge before it went into the engine and the other was the use of two small turbo-chargers rather than one big one. While those people with their heads in the sand were screaming “unfair”, others got on with the job of “joining them if you can’t beat them” and the first to go the turbo-charged 1 1/2-litre route was Ferrari, with Alfa Romeo not far behind.

At the time of writing Renault are still the only firm to have raced a turbo-charged 1 1/2-litre at Formula One, but the forced induction Ferrari is about to start its racing programme. Alfa Romeo are planning the introduction of their turbo-charged 1 1/2-litre V8 by mid-summer and already out on test are cars using turbo-charged BMW and Hart engines. After fifteen seasons of unsupercharged 3-litre engines, Formula One looks to be starting a new era of forced induction 1 1/2-litres with 4-cylinder, 6-cylinder and 8-cylinder variants. Renault showed the way into Formula One after Porsche and BMW had started it all many years ago, and few people seem to have paid attention to Indianapolis. At long last Formula One has caught up with the times and we look to be in for an interesting future.

In America the Garrett AiResearch turbo-charger led the way in units small enough to apply to a racing car engine, while in Germany the firm of Eberspach were first in the field. This German firm changed hands and became KKK (Kuhnle, Kopp and Kausch) and development is proceeding apace with both American and German units. These are the orthodox system of using the exhaust gases to revolve a small turbine wheel, with an air compressor on the same shaft, this compressor feeding high pressure air into the engine, with petrol being injected into the air stream just before the inlet valves. This system can be accurately described as “forced induction by means of an exhaust-driven turbo-charging unit” or turbo-charged for short.

In Switzerland the Brown Boveri company have been developing a new form of forced induction by a system they describe as “pressure wave supercharging” with particular reference in commercial diesel engines. Their system is patented under the trade name “Comprex” and in recent years they have been applying it to small diesel engines for passenger cars. Ferrari are experimenting with a Comprex system on their 1 1/2-litre V6 Formula One engine, with encouraging results. The Comprex system is directly driven supercharging, as distinct from exhaust-gas driven turbo-charging. Whereas in a turbocharger layout the intake pressure is proportional to the speed of the turbine, which itself is dependent on the flow of exhaust gas, the Comprex supercharger is positively driven by the engine and the exhaust gases merely provide the pressure waves to compress the incoming air on its way to the inlet-manifold. With a pure turbo-charger layout there is an inevitable lag while the turbine/compressor unit gains speed once the throttles are open and exhaust gases are flowing. With the Comprex the pressure-changing unit is always running in unit with the engine so that there is no time-lag while the unit gathers speed. The functioning of the exhaust gas pressure waves within the supercharger unit is somewhat involved and requires a knowledge of gas-flow to fully understand, but in its simplest terms the Comprex has a revolving drum into one end of which fresh air is led while high pressure exhaust gas is led into the other end. The pressure waves of the exhaust gases compress the fresh air as it passes into the drum and out again at the same end, while the spent exhaust gases exit from the same end as they entered.

Already the Ferrari drivers are enthusiasts about the installation as it does not have the lag in response that the normal turbo-charger unit has, and therefore it is much easier to drive the car. Although the well-proven unsupercharged Cosworth DFV engine will continue to hold dominance the signs are that engine development in Formula One will take a dramatic step forward in the next year or two.

Teams who are set on a turbo or super-charged programme are Renault with their V6, Ferrari with his V6, Alfa Romeo with their V8, Toleman with the 4-cylinder Hart engine and Brabham with the 4-cylinder BMW engine. Matra are developing a turbo-charged 1 1/2-litre engine for Talbot-Ligier, but as yet no details have been released. The immediate future looks interesting. – D.S. J

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