The Mazda RX-8 uses a counterweight. (Actually, on the manual-transmission version it's a flywheel that has a sort of lip around the rim that's thicker on one

The Mazda RX-8 uses a counterweight. (Actually, on the manual-transmission version it's a flywheel that has a sort of lip around the rim that's thicker on one side than the other.) Aftermarket flywheels are generally symmetrical, with a way of bolting on a separate counterweight piece. (The reason I know this is that I'm working on converting an RX-8 to electric. I got the car cheap with a messed-up engine, and I bought an aftermarket flywheel to replace the lopsided stock one because I don't want the car to shake itself to pieces. I haven't gotten around to ordering the adapter plate yet, but CanEV makes an RX7/8 transmission adapter plate along with two different versions of a coupler that attaches the motor to either a tapered-shaft style flywheel, which is what the car had originally, or a six-bolt variant for some other version of the engine.)