BMW Car magazine (August 2000, pages 22-26) has an article on a 500 bhp E39 M5. Nowack tuners (Germany) modified the car by first adding to intake hoses and free-flow air filters. Second, they lowered the charge intake pressure by coating the underside of the pancake airbox in reflective material to drop the intake air temp. by 24 degrees (20 bhp gain). Third they added to pairs of race-style exhaust headers with long primaries, which meet collectors just before a pair of free flowing metal catalyst (would this pass emissions testing in U.S.?). They also constucted 80mm diameter outlet pipes. Lastly, the cylinder heads were ported, and valves and seats reprofiled. Performance jumped to 503 bhp at 7700rpm with 465lb of torque at 3400 rpm.
My question is why can't these modifications be done by U.S. tuners (ie. Dinan or Hennessey). Dinan's website states that they can't extract any more hp from the engine, and I believe Hennessey's mods. are only good for 25-50bhp more.
My question is why can't these modifications be done by U.S. tuners (ie. Dinan or Hennessey). Dinan's website states that they can't extract any more hp from the engine, and I believe Hennessey's mods. are only good for 25-50bhp more.