 This made it impossible for Mercedes-Benz to use the engines from its previous Group C cars.Also, to produce similar power to the Group C cars a 3.5 litre naturally aspirated engine had to be very high-revving and be constructed from different materials in order to rev highly.Unlike Jaguar's XJR-14 who had the readily available and proven Ford HB V8 engine from the Benetton B190B Formula One car (the engine regulations for the new 3.5 litre formula were identical to Formula One), Mercedes-Benz had to design an all-new purpose-built racing engine and its M-291 3.5L Flat-12 unit was the result.