Modifications
Drivetrain
ESS Tuning Twin Screw 2 supercharger system
ESS Tuning is Europe's premier BMW supercharging specialist. The company is highly regarded for its supercharger kits for the M52 and M54 six cylinder engines, which used in BMW models between 1994 and 2005. No off the shelf supercharger kits for the Alpina Roadster S existed before the Roadster S Supercharged project was finished. The hand built Alpina E5/2 engine in the Roadster S is based on the iron-block S52B32 that was used in the North American E36 M3 and is closely related to the USA-spec M52 engine. Thanks to these close family ties the ESS Twin Screw supercharger system for the M52 engine could be fitted to the Alpina engine with relative ease.
The twin screw supercharger system for the Alpina Roadster S was developed as a custom project at the ESS facilities in Norway. The car was delivered to Norway in the first week of October 2008. Six weeks later the conversion was finished. The twin screw design creates a high boost-pressure at lower engine rpm, significantly increasing bottom and mid range torque. The Alpina intake manifold was replaced with the cast aluminium ESS intake manifold, which integrates a liquid intercooling system consisting of three 500mm Laminova cores. The liquid intercooler coolant is pumped through a high capacity front mounted heat exchanger. No modifications to the engine internals were made. The Alpina engine already uses light weight Mahle pistons to enable a redline of 7200 rpm and is equipped with a more aggressive camshaft profile than the ESS camshaft upgrade for M52 and M54 engines. The supercharger runs at a conservative boost pressure of just 7 PSI.
The supercharger conversion proved very successful, increasing torque with 20 tot 30 percent accross the rpm range. The system flows much better at high rotational speeds, shifting the point of maximum power from 6300 rpm all the way to the redline at 7200 rpm. Due to the increased torque at high rpm's, maximum power was raised by 39 percent to 445 HP. The stock Alpina engine already performed very well at 320 HP. Much of the character of the Alpina engine was preserved with the greatest difference the higher torque and better performance at high engine speeds. The engine is now the closest thing to a real high-revving M-engine without being one. Throttle response is very good, comparable to a naturally aspirated engine and much better than a turbocharged engine. There is still occasional off throttle kangarooring between 1100 and 1300prm, caused by the aggressive camshaft profile, but overall driveability is very good, even better than stock.
I have now driven more than 20,000 kilometers with the supercharger with the only engine related failure a cracked weld in the exhaust header.
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