Do cars with true SMG's (not semi-auto's with torque convertors) like the M3 or the MR2 have flywheels which can be chabged for lighter ones?

 

i didnt know the M3 and MR2's had true sequential gearboxes available.

as for the Prodrive and Quaife systems, yes, they have an actual clutch and flywheel.

 

That's what makes them different from the "tiptronic" automatic transmissions found on for example Preludes. "Tiptronics" are glorified automatics, using a torque converter and all that, but "clutchless" manuals actually have a clutch... just no clutch pedal. (Crappy naming convention.) They're computer-controlled manual transmissions.

 

Would the automatic clutch be able to compensate for a lighter flywheel, or just repeatedly stall the engine?

 

All depends on how smart the computer controlling it is, I suppose.

 

so does this mean you can swap flys?

 

You can, but no guarantees on it working. I'd do some research on boards for that car manufacturer before swapping... that's a lot of labor down the hole if it fails.