I've recently popped the motor in my third gen do to lack of fuel system. I a upgrading the fuel system and are just about to rebuild the motor. A fellow in town is recommending I use the lower compression rotors from a 87 or 88 (can't remember) turbo II second gen. He also has mentioned that besides being lower compression (8.5/1 ???), they are lighter meaning faster rev's ect.... What I am concerned about is since the compression of the motor will be dropped, the boost will need to be raised. But.... since the stock turbos aren't effecient at levels above 16psi won't this possibly hurt my performance unless I go to a single turbo? Am I in left field?

Right now my setup consists of.

Street ported motor with 3mm seals.

Downpipe, midpipe, exhaust, large ic.

Non-sequential's

pettit ecu..... but are ordering a haltech, 1600cc inj's, and fuel pump

I'm know the 1600's are over kill for my current setup, but I am looking to go single turbo in the near future.

My current setup is putting down 355rwhp on 13psi and pump gas. (well it's actually broken at the moment, but it did a few weeks back.)

Any insight?

 

While they are lower compression (8.5:1 vs. 9:1 on all '89-present turbo RX-7s) they are NOT lighter. '87-88 rotors are about 1/2lb heavier than the later rotors.

 

Stick with the newer rotors and the same weight. You could use lower compression but you will have to run more boost to make the same ammount to power, making the car use more fuel. It isn't worth it. The rotors out of an 89-91 TII are the same weight as your 3rd gen rotors and compression.

 

This really isn't recommended unless you run TONS of boost.&nbsp Yes, the 1986-1988 FC3S turbo rotors are HEAVIER.&nbsp Most people don't know that they are also a lot more STRONGER due to the extra weight.&nbsp Heavy boosted Japan rotary engines run the FC3S Zenki rotors due to their ability to resist deformation from detonation.&nbsp The FC3S Kouki and FD3S rotors seem to easily deform (on their leading rotor faces) from detonation at high boost.&nbsp I wouldn't recommend changing out the rotors unless you regularly seeing over 20psi of boost.&nbsp If you're keeping it around 14psi (or under 20psi), you'll be at an advantage to use the higher compression rotors.

FC3S Zenki = 1986-1988, or Aussies call them Series IV.
FC3S Kouki = 1989-1991, or Aussies call them Series V.



-Ted