BTCC VECTRA ENGINE

Body Shell | Aerodynamics | Engine | Transmission | Suspension | Interior

		The all new S2000 Vectra's engine is based on an L850 unit, a worldwide GM product, fitted to everyone's Vectra and Signum in 2 litre turbocharged form. The L850 is an excellent base for a naturally aspirated race engine combining an excellent cylinder head port design, a low friction valve train and a very rigid aluminium cylinder block. Eighty percent of the parts of the standard engine are replaced by parts designed according to FIA S2000 regulations in order to increase performance and achieve the required reliability. The regulations prevent the use of exotic material and limit the RPM to 8500 in order to keep development cost under control. They also limit the capacity to 2 litres, restrict the inlet and exhaust valve lift to 11mm and the compression ratio to 11 to 1 as well as specify minimum weights for the moving parts.
Engine is based on the L850 unit

The race engine development has been focussed on three areas:

Breathing efficiency:

It is the basics of engine performance increase: getting as much air as possible to fill the cylinders during each cycle, and, under S2000 technical regulations, without the help of forced induction (by turbo or supercharging)
Using a combination Computerised Fluid Dynamics and flow bench testing, the pressure losses in the inlet system, inlet and exhaust ports as well as exhaust system have been minimised.
Using Finite Element Analysis as well as specific software, the valve train is designed so that the valves are opened up to the maximum legal lift of 11 mm in the shortest possible time. The same philosophy is applied to the closing down phase. Rig testing, where dynamic spring load as well as valve position is measured accurately, is carried out to back-up the calculations and ensure reliability.
Using Performance Computerisation, the acoustic performance of both inlet and exhaust installations, valve opening duration as well as valve timing have been optimised in order to maximise the breathing efficiency between 7000 and 8500 rpm. Dyno testing backs up these simulations and concludes the breathing efficiency development phase.

Combustion & cycle efficiency: This chapter starts right back to the fuel injectors that are developed to spray the mandatory fuel as finely as possible. The position of the injectors in the inlet system as well as the timing of the injection will contribute to a good preparation of the fuel & air mixture. When the mixture travels to the combustion chamber, it needs speed. The more speed, the more it will become homogeneous. Lots of speed can be generated when the mixture passes the inlet valve, either sworl, where the mixture will be made to rotate around the cylinder axis, or tumble, where the mixture will be made to rotate around an horizontal axis. The inlet port as well as the combustion chamber shape can be altered to favour one or the other.
		The engine has undergone a rigorous testing and development program

The shape of the combustion chamber combined with the piston crown are designed so that a wide spquish area is available and so that it form a volume with as little area of heat exchange as possible in order to reduce calorific losses and therefore help the cycle efficiency.
Iginition is then the key. It is about where in the chamber the spark is positioned and when in the cycle the park is created. Both will have an influence on the combustion efficiency and moreover on the combustion duration –the shorter the better- which itself influences the cycle efficiency.
Our Performance Computeristaion helps us with the above but, most of these iterations are developed on the dyno.

Friction losses:

Finite Element Analysis helps the design of moving parts and, the reduction of plain bearing sizes. Low friction materials and coatings are used as much as the S2000 regulations will allow.
Ancillaries -water pump, oil pump, power steering pump, alternator- efficiency is minimised by design and, their drive, methods and dimensioning, is done so that, again, as less energy as possible is lost there.
Finally, it is the tightening of manufacturing tolerances that allow an engine to be assembled with precise and minimal plays between moving and static parts.
All this together will contribute to a low friction, and thus powerful, engine.

The above development programme has transformed a road car 170hp L850 into a race unit of nearly 260 Nm and 300hp.