The Vehicle


The Vehicle
The RM Dirtstar has been specifically designed to travel as fast as possible over cross-country courses with out falling apart or breaking (hopefully!).

It consists of a full tubular steel space frame chassis, built to RAC MSA specification with double wishbone suspension front and rear. The suspension has been designed with long travel (15″ front & 17″ rear) and the ability to cope with hitting hidden rocks at speed.

The transmission is a permanent four wheel drive arrangement with limited slip differential in the rear axle and an open one in the front.

The motor chosen was the Jaguar S-type V-6 due to its lightweight and potential for tuning.The engine is been fitted with a 5 stage dry sump system for optimum reliability as well as keeping the centre of gravity as low as possible; the prop shaft now runs through the centre of the dry sump pan!

Other engine modifications include worked heads and bottom end by CMT in London, Pauter conrods from the USA and 12.5:1 pistons from Wossner. Piper have supplied the camshafts with solid lifters to a spec that enables the original torquey motor characteristics to be retained. The whole assembly has been balanced by CMT and is safe to 9,000 RPM!

The gearbox is now an Elite IL300 4×4 unit, which is a 6 speed sequential unit featuring a built in transfer case and changable ratio’s.

 Due to the extra power and torque outputs BMW M3 EVO differentials are now employed front and back, these are fitted with shot peened and chemically hardened gears.

The suspension has also been updated with extra shock absorbers being added to each wheel and the geometry altered to give more rising rate on bump. The chassis was originally designed to have a 97″ wheel base, this has been extended by the redesigning of the wishbones on the rear to give 100.5″, making the car more stable at speed and over high speed bumps.

The radiator has also been located in the front of the car to change the weight distribution, this has improved the handling, especially on fast sweeping bends.

Further modifications have been carried out specifically for racing in France, these include fitting doors (great for cold wet meetings), fitting FIA seats and a bag tank, the rear frame has also been re-designed to allow a spare wheel to be carried within the confines of the bodywork rather than on the roof where it would raise the centre of gravity too much.

The work was carried out in 2007, with the car being ready for the end of this season. The results and times obtained have proved the car is one of the fastest in the UK showing good reliability and scope for more speed in the future.

One area that will be looked at is aerodynamics with a new body package being designed for increasing cornering speeds by using downforce and spoilers.

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