The Ford Escort RS Cosworth part 4

Of course the first series (big turbo) of the Escort RS Cosworth was the "homologation" base used for the rally cars. The major competitors in WRC (those with the most sponsors and subsequently the most important budgets) had cars which remotely resembled the base (production) car but were light years away from it mechanically. Here are the major changes in the Group A car as compared to the production car:

Chassis are reinforced (roll cage), seam welded and many new welding points are applied.
The suspension housing tunnels are reinforced with welded upper aluminum/titanium plates to allow suspension angle adjustment
The suspension layout is modified (it has to retain the same principle as the production car i.e. McPherson) so that all angles as well as the ride height are adjustable in situ. The rear suspension also uses a McPherson layout which was later replaced by a multilink layout in the Escort WRC car. Shock absorbers are liquid cooled and non linear (progressive) springs are used
The brake system is completely free in GroupA. No ABS or servo assistance is used. There are two brake circuits and two master cylinders. The front brakes (depending on the type of rally) are usually Ø378mm with 8! pot calipers and 4 brake pads each. Rear brakes are Ø315 with 4 pot calipers. The front brake calipers are water cooled with separate water pumps, radiators and reservoirs. Braking force bias (front/rear) can be changed from the cabin
The gear box used is an MS95 7 speeder (non sequential) with the first ratio removed. Dual plate carbon dry clutches are used. The gear box uses an oil pump and an oil radiator to keep cool. (Note that this gearbox was replaced by an X-Trac sequential one since the New Zealand '97 rally)
The steering is a rack and pinion based high ratio (12:1) with 2.4 turns from lock to lock. Servo steering assistance is available. The steering oil uses a radiator for cooling
A bigger intercooler is fitted in a different location than in the production car. Additional cooling is provided by an external water spray system. Air intake temperature is always around 40°C ! Water injection is also fitted
The fuel tank is re-located inside the car's trunk and is compliant to FIA regulations (80 lt. capacity)
The engine is heavily modified. The crankshaft is made of a single piece of steel and is lightened and balanced. Titanium driveshafts are used as well as forged aluminum pistons. The outlet valves have lithium inlays. The engine head is polished and wider valves are used throughout. The camshafts are specific, the compression ratio must be around 8.5. An FIA 34 mm restrictor is used on the turbo. Two high pressure fuel pumps are used. Two supplementary liters of oil are used, compared to the production car (a total of 8lt). Magnesium oil sump. Turbo boost pressure is in the 2.5 bar+ region. Bang-bang switchable from the cabin
The transmission system is also completely different than the one fitted in the stock car. Three self locking differentials are used. The center and front ones are computer managed. Two hydraulic pumps feed them with pressure (0-50 bars). The computer management can be overridden by the driver who can adjust the torque distribution, between the front and rear axle using an onboard button. The center differential is automatically disconnected whenever the driver pulls the parking brake. All differentials are connected to oil coolers
The electrical system is completely redesigned and complies with aviation standards (i.e. pricey)
18" magnesium wheels are used on tarmac
The car's laden weight is 1230Kg

You realize why works cars used to cost from US 500,000 up and why only few drivers could get their hands on them. There are extremely few parts that have their origin in the street version, if any.

The Garrett T35 turbocharger and Cosworth YBT engine

Ford says that the engine's output is 300 Bhp with the 34mm turbo restrictor fitted (as does Lancia, Mitsubishi, Subaru, Toyota and others since this number is the maximum set by FIA regulations). Of course no one believes them since you can get that kind of output from a stock Escort Cosworth with minor engine management modifications. I'll quote Didier Auriol's co-driver, Denis Giraudet, who once declared: "Last year we had 300PS. This year we still have 300PS after changing almost all engine parts and running at least 1 sec faster/Km..."

A better guess is that these cars must have an output of at least 350 Bhp with the 34 mm turbo restrictor fitted. Ford Motorsport claim a 3s 0-100 Km/h in any conditions (including gravel)!

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