while there's a lot in common between the 1983 10V turbo engine and
the 91 turbo 20V, i think there's even more differences. as you've
noted there's a slight capacity increase..
other major differences that i can think of:
- much more advanced electronics to manage
boost/ignition/injection. the spectacular 2000 rpm torque peak and
near elimination of lag is in large part achieved by smart wastegate
- and also a very very high (for a turbo) compression ratio of
9.3 to 1. i believe the original turbo was only 7 to 1.. so new
pistons (?) and knock sensing electronics have to be added.
- water cooled turbo for long life though i suppose you can pass
- the flywheel is now a compound dual mass, liquid damped one and
it is also lighter, so the engine can now spin more freely as well as more
though i know very little about modifications, this project seems
really ambitious.. personally i would explore instead the idea of
transplanting a complete 20 v turbo either from an s4 or 91 200Q
rather than try to use the existing engine.. now that i think of it,
i don't even know if there are any parts in common between the 83 10V
turbo and the 91 20V turbo..
good luck and keep us informed..