RALLYCROSS – WHAT’S THE SECRET?

What is it that makes a Rallycross engine capable of such monumental power? We had a brief chat with Julian Godfrey to find out. He couldn’t give all his secrets away of course, but he did explain the importance of building a strong engine. With this in place, the upgrades to fuelling, turbocharging and cooling can all play a part in making lots of reliable horsepower.

The engine in Tim’s car is built on a 4x4 200 block because it physically has the material for a long-stud conversion, which prevents the cylinder head from lifting off the block. The block itself is strengthened by one of Julian’s own dry sump systems, which also provides a more reliable source of lubrication under the immense G-forces that slick tyres can give. The bores have Nikasil liners and the bottom- end components are billet aluminium and methodically balanced, so the engine spins up really quickly.

Julian says the turbo is fairly straight-forward, essentially a T04S with a 61mm compressor wheel. You can see the turbine housing is ceramic- coated to keep the heat in. Perhaps surprisingly, Julian also says the 58mm restrictor that Tim has to run for the Motorsport News Championship probably restricts the engine to around 800bhp. It’s not really an issue for a Cossie, it seems more of a preventative measure against big- capacity monsters.

The motorbike-like idle sound is probably a result of the cams, mixed with the lightweight rotating assembly inside the engine. The cylinder head is a CNC’d thing of beauty, another Julian Godfrey piece of the highperformance puzzle. However, Julian says the cams are not actually a really aggressive profile, not when compared to the latest Rallycross engines which run even more overlap for example.

All this power runs through a Quaife 87G gearbox, a super lightweight clutch and flywheel and eventually through huge, clunking differentials front and rear. The same diffs as you’d find in a GT racer, according to Tim. A strong set of diffs and driveshafts is critical to matching all that torque with the grip of sticky slicks.