soloracer951

Are they the same as T2 rotors (early or late)? Are they the same as FD rotors? Or are they unique to the 20B?

Jeff20B

iTrader: (13)

S5 '89-'92. Zenki or something. RETed would know that. FD rotors are probably the same.

Turbo 3

iTrader: (3)

They are the same as the FD and FC S5 TII far as I know, the have the same compression and they are interchangeable.

onefastrx7turbo

iTrader: (5)

they are the same as S5 T2 (kouki) and FD...the machining is different between the different motors, but the weight, and the compression ratio is the same

soloracer951

What do you mean by "machined different"? Does this imply that even though they are the same weight and same compression they can't be switched between engines?

RETed

Cosmo rotors are identical to Kouki FC3S turbo rotors.
Compression is 9.0:1.
Tubs are machined.

FD3S rotors are identical weight and compression.
The difference with FD3S rotors is that they are machined on the entire face.
The extensive machining is for tighter production tolerances.


-Ted

DMRH

Dude. The series-5 ran from 89-91. Production ceased in Sep-91. The series-6 started production in Nov-91 hitting Japanese streets in Dec-91. The series-6 hit the world stage in early 92 including the USA.

The JC rotors (90-95) are practically identical to the FD rotors (92-02).

REgards

Jeff20B

iTrader: (13)

Sweet!

RETed

Can you show us proof of the fully machined faces from a Cosmo engine?
So far, all the rotors I've seen out of Cosmo motors don't have machined faces but only machined tubs.


-Ted

soloracer951

When you say "machined" what do you mean exactly? Do you mean that the old rotors were "cast" and that the newer ones were machined out of billet?

And just so that I am understanding correctly you are all saying that FD and series 5 rotors can be interchanged into a 20b with no extra modifications needed? Do you need to match rotors or can you go with different rotors in each housing? Can you have a 20b running with 1 fd rotor, 1 series 5 rotor and 1 20b rotor?

Auto Illusions

i was told that they are the same as the fd rotors spec wise but the fd has a better cast and stronger stationary gears....... just what i was told!

RETed

All of those rotors are cast.
On the rotor faces, there is the "tub" sunken portion and the higher flat surface.

Older design rotors were purely cast with almost no finishing on the rotor surface.

The Kouki / S5 FC3S was the first time Mazda started to machine the tubs for tighter tolerances of the compression ratios. Previous to this, CR's could be off by as much as 0.4; after Mazda started to machine the tubs, tolerances were tightened down to 0.06.

With FD3S rotors, the entire rotor face was machined. If you look carefully on a clean rotor, you'll see the machined lines on the face.

All of the Cosmo engine rotors I've seen from 13B-RE's and 20B-REW's all had machined tubs with no machining on the rest of the rotor face. These are identical to the Kouki / S5 FC3S rotors. DMRH mentioned Cosmo rotors should be the same as the FD3S rotors, but I've never seen them in my experience.

That is basically correct.
All the rotors (make sure it's an S5 / Kouki FC3S *turbo* rotor) are 9.0:1 compression ratio with idential weights.


-Ted