I'm officially derailing this thread since the author has abandoned the project.
The rev limit used to be 19k in F1. New rules for this year limit the engines to 18000 rpm. MOST of the KERS systems store energy as electricity obtained under braking in large capacity batteries. When put to use, the electricity is fed to a motor (an electric motor, not the engine Nascar guys ) that is somehow hooked up with the drivetrain to provide a boost when used.
The exception is one of the Bimmer teams which uses some sort of sophisticated flywheel to obtain or store energy.
I think.