david_12121

Hi guys,
hopefully I'm posting in the right spot.

I'm putting an s1 rx8 trans on an s5 NA FC engine. I know it's weaker, it fits the application(not an FC) much better and I can get an S2 trans if it has issues.

For clutch stuff, I am unsure what I can do.
to my knowledge, the S5 NA needs an s5 NA flywheel.
And the rx8 needs a 240mm clutch from an s4 turbo.
S4 pressure plate won't bolt on an s5 NA flywheel.

Am I wrong? Is there a solution that doesn't involve a different rotating assembly?

Thanks

Dak

I thought the S1 Rx8 trans was stronger than the FC n/a one but weaker than the TII trans, but it takes high rpm's better than the TII.

As to the clutch.The S5 engine needs a S5 rear counterweight. It is built into the stock flywheel on the manual trans cars. The autos have a separate counterweight that bolts to the flex plate. So you need either a stock S5 TII or 3rd gen( 3rd gen uses the same counterweight) flywheel. You can also use an aftermarket lightweight turbo flywheel and s5 counterweight from a S5 auto trans car. Then you just use the TII clutch of your choice.

david_12121

Is the Tii S5 flywheel counterweight the same as S5 NA? Also the same as the S5 auto bolt on counterweight?
So it seems like I can just get flywheel, clutch, pressure plate for an s5 Tii. And throw out bearing for s1 rx8 and I'm good to go?

Dak

Yes and no. The weight of the S5 counterweight is the same across all of them. Physically they are different. The stock flywheels have the counterweight built into them as a part of the flywheel. On the automatic it bolts to the flex plate as a separate piece. All aftermarket lightweight flywheels don't integrate the counterweight into the flywheel like stock but use the auto counter weight instead. So yes if using an aftermarket flywheel you use the same auto counterweight for the TII and the n/a. Stock it's part of the flywheel so you don't have to worry with it. So yes get the stock S5 TII flywheel or aftermarket flywheel of your choice + S5 counterweight and clutch of your choice and Rx8 throw out bearing and you're good to go. Maybe? I do recall having to do something with the slave cylinder but I don't remember if it was chassis related or it was something to do with the oil filter pedestal. There's a thread on here somewhere that talks about it.

Browse around this Mazdatrix page. https://www.mazdatrix.com/vehicle-ye...lutch-flywheel

david_12121

Got it. I'll post a confirmation when i assemble it all. Thanks guys.

david_12121

Today I tried to drive the car, having an issue.
The clutch isn't disengaging.
It is bled properly, it has almost no slack, and I adjusted it all the way up. Feels super normal but won't let me get into gear.
The internet says both the rx8 and Miata clutch master cyls are 5/8 so I'm lost.
Any ideas?

fidelity101

iTrader: (11)

you need to use a turbo or rx8 style clutch to use the rx8 gearbox on a FC engine.

david_12121

It's an FD flywheel, turbo II clutch and pressure plate, rx8 throw out bearing, rx8 clutch fork, rx8 slave cyl, Miata master cyl.

fidelity101

iTrader: (11)

the rx8 slave cylinder wont fit the 13b S4/S5 block. Use a slave cylinder from an Acura integra.

you need FD rotors to run the FD flywheel or you will be out of balance in your rotating assembly.

the rx7 clutch master cylinder is fine, why do you need to change it to a miata one?

Dak

I thought the S5 and FD rotors were the same weight and thus the flywheels(between the S5TII and FD) would be interchangeable. Mazdatrix list the same rear counterweight for all 89-95.

Yeah I wondered why the switch to the Miata master cylinder. I didn't recall mention of that in any of the Rx8 gearbox threads.

david_12121

Yea I think the FD counterweight is the same as S5.
and RX8 slave sits on the rx8 trans, it'd hit the stock oil filter but mine is relocated.
miata master because it's in a Miata. It's 5/8, like the FC and RX8 so it shouldn't matter.

I have ordered a new rx8 slave, Miata master, and Land cruiser master (3/4")
Will find out soon if it's those things.
​

fidelity101

iTrader: (11)

I missed the "in a miata" part.

you should be good to go then, just run your stock clutch master. I run the same and ive used s1 and s2 manual transmissions in my FC.

david_12121

Changed the slave to a new rx8 unit.
changed the master to a new Toyota 3/4 unit.

It moves the clutch fork more but it still doesn't disengage.
So as a sanity check, I shouldn't need a spacer between the flywheel and the pressure plate, correct? Pressure plate mounts directly onto the flywheel.