Is there anything that needs to be done to run fd rotors in an fc to be able to run the bigger apex seals?

 

89-91 FC turbo rotors are practically the same as the FD rotors. You can swap them without a problem. Not sure what you mean by bigger apex seals...

 

I have an 88 t2...I mean 3mm as oppose to 2mm

 

FD rotors are 2mm, they would have to be machined to use 3mm. To install FD rotors in a S4 car you also need the front and rear counterweights (or flywheel).

 

So what car has 3mm seals stock?

 

First gens came with 3mm seals. Everything pre- '86.

 

Aiight thank you

 

technically the only 13B engines that had 3mm seals were the 74-78 early 13B engines from the REPU and RX4 as well as the 84-85 GSL-SE. those rotors are all 9.4:1 compression and are 3mm OE seals. as with any series rotors you need the counterweights from those original engines.

the early 3mm rotors were also the heaviest weighing in at about 11lbs each.

 

9.2 compression on the early rotors.

 

not sure i believe that quoted figure. the REPU pockets are .6mm shallower than S4 n/a rotors and the whole tube is cut smaller in diameter. the pockets actually most resemble S5 n/a rotors but the S5 are shallower yet but the recession cutout is larger.

GSL-SE rotors do conform to the more modern 2nd gen pocket design. you're probably right that the REPU/4 has a different CR but i'd have to do more measurements to agree that it is lower, the rotors themselves would have to be smaller to compensate or the radius less.

i've heard people even claim the GSL-SE rotors as 9.2:1 which is false, the cutout is identical to S4 n/a pocket design.

edit: checked the REPU rotor and it has the same radius and rotor dimensions, the recession is one of the smallest of all series to date so i have a hard time believing it is a 9.2:1 with the dimensions i checked against other rotors. the tochoidal face of the housings is also identical to newer housings so it wasn't lost there.

i'd almost believe they were 10:1 rotors by staring at them and comparing versus all the other rotors, the main difference is the edges slant sharply, giving it a little more volume there.

 

It's generally accepted, but could be incorrect. I was going with what Mazdatrix and Dave Atkins said. I've never actually measured them myself. Sorry I parroted there.