Its my understanding (or misunderstanding) that the FD rotors are lighter and slightly lower compression (9.0:1 vs 9.1:1). I'm in the planning stages (well actually collecting all the parts) of building a turbo motor for my GXL. I recently purchased a J-Spec FD motor which will be going in my FD, so I have some FD parts lying around.

I would put the FD motor in the FC but dont feel like tapping holes in the housings to match the motor mounts and I believe I'd have to modify the oil pan as well.

So basically my thought is to use the FD rotors in the J-Spec TII motor to run higher boost and use an FD transmission. Does this sound reasonable or is it a waste of time.

 

Uh, no.

All 89 - 91 FC turbo...
93+ FD...
All Cosmo 13B and 20B turbo...
...use 9.0:1 compression ratio rotors with identical weights.

The castings have subtle differences, but it's the CR and weights that make the most difference to keep the engine from shaking itself to pieces.


-Ted

 

So you think it would be worthwhile to rip the J-Spec apart and put in the FD rotors or should I just hold out until its time to rebuild anyway.

 

I wouldn't use FD rotors, period.
FD rotors dent under detonation.
If you're going to be running high boost, I'd even drop down to a Zenki S4 FC turbo rotors @ 8.5:1, slightly heavier, and stronger - i.e. resists detonation better.

No reason to run FD rotors over the S5 FC turbo rotors though.


-Ted

 

Amen.

 

I agree also with the above statements. And if you plan on running very much boost don't even consider high compression rotors.

-Destin

 

more people should pay attention to this.

 

more people should pay attention to proper balancing