Engine and drivetrain
Performance modifications started with an upgraded engine, which was enhanced by Lotus from the standard Opel 3.0 L (2,969 cc) 24v straight six unit (used in the GSi). The engine was enlarged to a capacity of 3,615 cc (3.6 L; 220.6 cu in). Lotus then added Garrett AiResearch T25 twin-turbochargers, which provide up to 0.7 bar (10 psi) of boost from about 1500 rpm. The original distributor ignition system of the engine was replaced with a three-coil wasted spark system. The distributor drive was re-purposed as a water pump drive for the water-air intercooler circuit. The intercooler itself is manufactured by Behr and is capable of reducing the temperature of the compressed charge from 120 °C (248 °F) to 60 °C (140 °F).
In addition to fitting two turbochargers and an intercooler system, Lotus directed a number of engineering changes to the engine so that it would perform reliably with the higher power output. To cope with the higher cylinder pressures (about 95 bar (9,500 kPa)), the external webbing on the engine block was reinforced. The crankshaft was replaced as well; early development crankshafts were machined from billet steel in Italy, but the production units were forged by Opel and sent to Maschinenfabrik Alfing Kessler for machining. The cylinder head was left mostly the same as the 4 valves per cylinder from the Opel Omega, although the combustion chamber was milled to reduce the static compression ratio to 8.2:1 (from 10.0:1). The engine is fitted with forged slipper pistons produced by Mahle. Piston connecting rods were replaced with new units made to an original Lotus design.
The same ZF 6-speed manual transmission as fitted to a contemporary Chevrolet Corvette ZR-1 was used to transfer this power to the rear wheels via a rear limited-slip differential from the V8 Holden Commodore.