Formula One Trend of Design

Exhaust Systems

In the early days of racing engines, when most of them were supercharged, the exhaust gases were more or less left to their own devices to find their way out into the atmosphere, a simple tail pipe leading them away from the cockpit area, especially with front engined cars. When superchargers were discouraged and interest turned to normally aspirated engines a lot of thought was given not only to the ingoing charge, in the form of ram-pipes and air boxes, but also to the outgoing gases, and exhaust pipes took on a special art. Tuned lengths and diameters to take advantage of pressure-drop and pulsations were found to give better engine breathing and encourage higher revolutions per minute. Using one cylinder to help another one also proved important and exhaust system design was closely related to firing orders. Today the science of exhaust pipe tuning is a very exact one, and presents few problems, the main ones involving space, weight, and the dexterity of the pipe bender.

Since the interest shown in air flow over, or under the racing car, the exhaust system has taken on a new importance, not for its own sake, but for the sake of the air-flow and its interruption by the pipework. A close look at today’s Formula One cars will show very little similarity in design or layout, every designer having his own ideas on how to get rid of the exhaust gases without disturbing the air flow over or under the car. On those cars using the Cosworth V8 engine there are seven distinct differences of opinion. Basically they all conform to the system whereby the two exhaust valves to each cylinder feed into a single manifold pipe, and the four pipes each side join into a single tail pipe, with the convolutions of the four manifold pipes made such that they are all the same length between the valves and the junction with the tail pipe. Each bank of cylinders carries the same layout, and before the advent of under-car air-flow the tail pipes found their way out through the rear suspension members to protrude out the back on each side of the gearbox. When Harvey Postlethwaite and Colin Chapman started work on their clean-air-under-the-car theory the first obstruction they removed was the exhaust system. This they did by curving the “header” pipes upwards around the cylinder head and then in to the centre of the car, where the four pipes joined, and the tail pipe then protruded rearwards close to the centre-line of the car. This layout was used on Wolf WR5 and WR6 and on the Lotus 79. It was a very neat and effective system which allowed a lot of air to flow under the car on each side of the engine and has been copied on the Tyrrell 009, the ATS, the Williams FW07, the Ligier JS11 and the Merzario, all of them having the two tail pipes close together above the differential housing, with individual variations as the angle at which the pipes point rearwards. The Tyrrell and Williams point upwards at an angle of about 30-degrees, while the Ligier point rearwards almost horizontally. The Lotus 80 has a similar configuration but with the two tail pipes pointing almost vertical. Some designers are conscious of the blast from the pipes and its effect on the flow of air across the tail, others do not bother.

On the 1979 Wolf, the McLaren M28 and the latest A2 Arrows the right and left systems are kept entirely apart. From each cylinder head the four “headers” curl up and over, join into a tail pipe and then run rearwards. The Wolf WR7 and WR8 have elliptical section tail pipes that rest on top of the rear suspension cross-beams and are almost invisible to the casual glance, the whole system being concealed beneath the honeycomb upper body panels and the tail pipe not extending beyond the cross-member. The McLaren M28 uses a similar layout, but with a circular tail pipe and it merely lays across the rear suspension members. The A2 Arrows has its tail pipes protruding through the body panels and pointing upwards at quite a steep angle. The ill-fated Fittipaldi F6 of Ralph Bellamy took a unique and novel approach, with the “headers” joining together inside the side-pod and the tail pipe running forwards and then turning at a right-angle to protrude through the side of the pod. The old F5A Fittipaldi which was designed on the pre-ground-effects principles, has the tail pipes running rearwards through the rear suspension members at a low level, and the Shadow DN9 has a similar layout.

The three 12-cylinder engines in Formula One, namely the flat-12 Ferrari, the flat-12 Alfa Romeo and the V12 Alfa Romeo have only one thing In common and that is four tail pipes, each fed by three cylinders. The T4 Ferrari is a masterpiece of intricate pipe work, especially when it is born in mind that the exhaust ports are underneath the engine, as on the flat-12 Alfa Romeo. The Ferrari uses four small diameter tail pipes, two on each side of the car, curling up and over the transmission. With all four systems having the same tuned length it results in two seemingly long tail pipes from the rear half of the engine and two seemingly short tail pipes from the front half of the engine, each pipe being served by three cylinders. The short pipe on the left is served by cylinders 1-2-3 and the long pipe by cylinders 4-5-6, and similarly on the right-hand bank. The flat-12 Alfa Romeo engine was not concerned with serious ground-effects so the four tail pipes end in megaphones, under the rear suspension, two on each side of the gearbox and the “headers” are like the Ferrari in groups of threes. The V12 Alfa Romeo engine was conceived principally to encourage air-flow under the car and through the side-pods, so the exhaust system was important. Still in groups of threes to a tail-pipe the pipes on each side curl up and over and turn in to the centre of the car and then turn rearwards to form a cluster over the gearbox, pointing slightly upwards and at the pillar supporting the rear aerofoil. At Dijon these tail pipes were fitted with deflectors held on by clips, to take the hot gases away from the rear aerofoil.

Entirely on its own is the V6 Renault-Gordini engine, for it uses its exhaust gases rather than disperse them regardless. Each bank of three cylinders, like all the other engines with two exhaust valves per cylinder, feeds into a large-diameter tail pipe which is fed into the turbine part of a turbo-charger installation. Having driven the turbine the gases then exhaust out through another tail pipe which ends in a megaphone, to encourage extractor effect. The wastegate, or blow-off valve of the compressor unit has its own tail pipe and this runs parallel and to the outside of the main exhaust system also ending in a megaphone. The result is that the Renault presents four tail pipes pointing rearwards over the gearbox, two large-diameter ones emitting exhaust gases and two small-diameter ones emitting highly compressed air when the turbines generate more pressure than the system wants. On the first two twin-turbocharger cars all four pipes ended in megaphones, in a shape that encouraged the gases to rise upwards; the third car has the pipes ending in very shallow megaphones.

All these configurations aimed to get the pipes out of the under-car air-flow have brought about additional problems such as the ability to assemble the system, let alone make it, but the main one has been heat dissipation, especially on those that have the pipes totally concealed within the bodywork. Fortunately aircraft heat-resisting aluminium foil does a good job and everything is lined with this, but even so you still get the smell of burning fibreglass in the pits occasionally. The Ferrari and Alfa Romeo engines use Titanium tubing and sheet for their exhaust systems, to negate the handicap of four more cylinders than the Cosworth, but it costs a lot of money. The V12 Alfa Romeo also holds each “header” on with a single stud situated between the two exhaust ports of each cylinder, in another weight-saving detail. The art of bending exhaust pipes is a highly specialised one and the current crop of Formula One cars gives the specialist pipe-bender the opportunity to demonstrate his art to a very high order. — D.S.J.