[silversprint]

Depends how much you willl remove from the car. A full race car with the most of the dash, interior, door glass, and rubberized insulation inside the car removed will weigh around 2500lbs bare. Adding a full cage race seat, and fire system will still keep the car under 3000lbs.

If you are still keeping the car a street car and then it will be probably 3000lbs. Most of the rear shelf stuff has to be removed to install a proper cage in the car.

Everything in a Z4 is heavy as with any modern BMW. They are meant to be cushy street car marketed as sports car. There is a lot of weight that can come out.

The car would be competitive however it's expensive to build one.