Heres some info about the group b rally cars.
Audi Quattro sport-
Came in as the first AWD rally car and took the world by storm. nobody could match its pace. An equally wild engine.
The 2133 c.c. all-alloy 5-cylinder unit had 4-valve head plus a big turbocharger. Maximum power in race car reached 500 bhp, while the road car still managed to put out 300 bhp.
In terms of technology involved, it was quite advanced - spaceframe chassis, mid-mounted engine, Kelvar body for race car or honeycomb-structured glass-fibre body panels for the road car, 4-wheel drive, twin absorbers in each corner.
The engine was a 1.8-litre 16V turbocharged four-cylinder, made 250 bhp in road trim, but suffered a huge turbo lag due to the high inertia turbo attached for more power. Not very successful.
Lancia Delta S4-
the Delta was built for only one and one purpose only. Beating the Audi and peugeot. And it would have done it if it wasn't for fate.
Mid-engined layout.The engine was longitudinally mounted behind the front seats, directly driving the viscous-coupling LSD which transfered 30% torque to front wheels and 70% to the rear. Space frame chassis.
Engine was another Marvel.
It used a Turbocharger and a Supercharger simultaneously!!
Turbocharger is generally regarded as the most efficient means of forced induction, but it requires higher revs (hence a lot of exhaust gas) to operate. The result is poor low-speed power and the presense of turbo lag. On the contrary, supercharger performs strongly and instantly right from idle, but it is rahter inefficient in high rpm. For a rally car, a flat torque curve over a wide range of rpm is always very crucial, since rally car has to brake to very slow in tight corners and then accelerate to near top speed in 10 seconds. Therefore Lancia spent a lot money with Abarth to develop a system combining both turbocharger and supercharger to get a perfect output. It employed twin intercoolers, one for the turbo and one for the supercharger. The supercharger worked at low speed. Once the turbo cut in, a bypass valve relieved the pressure from the supercharger so that energy efficiency was be lifted.
This system was not only complex, but also faced great difficulties during development. The biggest problem was the transition between supercharging and turbocharging, since a short zero-boost period existed. However, after further developement, this problem was eventually solved.
As a result, the 1.8-litre engine of the rally car had at least 470 bhp on tap.
Peugeot 205 Turbo 16-
Peugeot 205 T16 represented a new generation of Group B cars which could eat the old generation (headed by Audi Quattro Sport) for breakfast. While Quattro Sport was still front-engined, with a heavy monocoque chassis, Peugeot redefined the rules as mid-engined with a space frame chassis.
The 1.8-litre 16 valves turbocharged four generated up to 440 hp in race form, and had a unique center differential which enable on-board selection of different torque slit ratio between front and rear axle.