Originally Posted by Invadermoose
I have a 2008 Convertible M3.
The problem is you can bolt on only 15-20% horsepower short of a supercharger and you have a heavy convertible that weighs 10% more than a sedan or coupe and you need the majority of any non forced induction gain just to get you to the level of a regular M3.
The M3 is already weak on torque. Saddling it with all the extra weight of the convertible makes it even weaker.
Even the centrifugal supercharger, the only forced induction option for these cars, adds relatively little torque, so you still have to run the car to redline to make big power.
I'd look at a new twin turbo M6 convertible or the performance versions of the Camaro and Mustang convertibles that also have about 550 lbs torque. Torque is what you want for satisfaction when you have a 4000 lb car.