How hard would it be to mount the RX-8 6-speed tranny to an FD? Has anyone looked into it?

 

its not going to fit, the tranny is a miata tranny. Also, if your FD has mods it will snap it like a toothpick. The tranny was not designed for high torque.

 

IIRC the bellhousing/block pattern is completly different between the 13B REW and the Renisis(SP), but I dont know if the bellhousing/trans pattern is the same for both.

 

The RX-8 tranny is WAY too weak for an RX-7... The gear ratios are also totally wrong and it would suck to drive it anyhow.

Brian

 

You're better off getting a higher ratio FD (final drive) anyways.

 

And this has been asked quite a few times, search next time.

 

Not even for the rotary version of "high torque"...

 

I'm gonna bet money that JimLab quoted something I said. I wonder what it was? Probably making some comment about how my renesis sucks. Just a guess.

 

Actually Brian, the RX-8 tranny is way too weak for even the RX-8

Ryan (DontBeARikki) snapped the tranny on his BRAND NEW RX-8 i believe within a month of gettin it...

granted, it wasn't made for 9000rpm launches lol...but still...

 

Yup, it's too weak.

 

ok thanks guys. guess I'll have to save up for the Hewland six speed sequential dog-box!! Whenever I get $25,000!

 

LOL

 

Actually, if I understood him correctly, Ryan's doing the exact opposite

After the tranny broke on his RX8, I believe he put an FD tranny in the 8...

 

Hope you enjoy 90+ dB of gear whine driving down the street....

 

Is there any reason to want to change out the FD tranny? I was under the impression it's pretty strong, doesn't give many problems...given the amount of abuse it takes?

 

The stock 5-speed is just fine if you don't powershift it, miss the 2nd to 3rd shift, or expect it to hold up to a lot of 7,000 rpm launches.

The people who think a 6-speed would automatically be better are probably the same type of people who think the RX-8's 9,000 rpm redline is a technological advancement over the RX-7's 8,000 rpm redline because it's another 1,000 rpm... never mind WHY the Renesis needs another 1,000 rpm...

 

JimLab...I know you're one of the more knowledgeable guys out there, so I hope ya don't mind all the ?s...

I take it the "missing the 2nd to 3rd shift" is grinding 5th, breaking the notorious 5th gear synchro, correct?

*Newbie Question Alert* lol
Powershifting...is that when you hold your foot on the accelerator, throught the shift?

And would ya care to share why the RX-8 needs another 1K of rpms? You got me all curious...

 

FDNewbie,

the 1993 rx7 had a problem from missing 2nd and going into 5th would cause the syncro to break. My car is a 1994, I have had many, many drag strip runs (probably close to 80 or 90) and while I missed 3rd gear 2 times I never broke my syncro. I believe that issue got fixed. As far as an rx-8 needing 1000 RPM more its because there are no turbo's on the rx-8. Having said that, while the torque is low (160 lbs), prioir to 2500 RPM there is clearly more torque in the rx-8. Also, the engine is far superior to the Rx-7's. The torque curve on the renesis is very flat and 90 pct is available at 3000 RPM. Having said that, the car is geared so you are always in a good power band (save for 6th gear). If you compare the FD's engine with higher compression (comparing it n/a the compression would be higher, take the turbos off the FD you would be about 150 HP or so) you would be about 160 HP vs the 238 HP of the rx-8 (247 for japan versions). Even if you put the redline on the rx8 at 8000, it would have alot more power than the 13B-rew.

Lastly, the FD's transmision is pretty damn bullet proof, the diff is more likely to break. I was told by a repair shop that the FD tranny started out as a ford bronco's transmission. I dont know if thats true, but that could explain why it can handle so much torque.

 

ZeroBanger...lol (I have no idea what that name means, but I love it haha)

Yea I figured it was the 5th gear synchro he was talking about. I dunno if it was resolved in later models tho, cuz I have a 94 and the 5th gear synchro was broken on it when I bought it. I had it replaced a cpl months ago, and put on a B&M shortshifter, which I believe has a 5th gear lockout mechanism when coming from 2nd...so you won't miss and break the synchro...

and yea i figured the 1000rpm more had to do w/ torque. so has anyone thought of swappin the FD engine w/ the 8's, and puttin FD twins on it?
disclaimer: im sure it's not as easy as I just said it, and im guessing there would be issues of building a N/A engine to handle turbocharging, etc... but still, if the 8's engine is that superior to ours, it's a thought worth tryin out, yes?

ive also heard many many stories of ppl breaking the diff., hence upgrading to the KAAS diff for their 7000rpm launches haha. but like you said, i got the sense the tranny was pretty strong

anyone wanna chime in on powershifting?

 

Correct.

Yep. Shifting without "lifting".

Because an engine is nothing more than an air pump. The more air and fuel you can put into it and burn in a specific period of time, the more power you'll make. There are three ways to accomplish that...

1. Increase displacement
2. Increase rpm
3. Forced induction (turbocharger, supercharger)

Since the Renesis isn't turbocharged and has very little displacement (and adding more isn't really an option), your only option to make more power (short of adding a turbocharger or two) is to turn more rpm. In order to reach the 238 horsepower (or whatever it is they're claiming now) output, Mazda had to make the engine turn more rpm.

Of course, the downside of a small engine turning a lot of rpm is that the powerband is unavoidably very narrow (often referred to as "peaky"), pushed towards the very top of the rpm range, and the engine makes no real power below that range.

Therefore the 1,000 rpm "advantage" of the Renesis over the 13B-REW isn't really an advantage at all... it's more of a side effect of the design and an indication that the Renesis isn't a better engine (from a power standpoint) than the 13B-REW at all.

Of course nothing illustrates this deficiency better than a comparison of their power curves (see the chart of actual dyno results below). People looking only at the peak numbers for both engines would say "well, 238 isn't that much less than 255". Isn't it? Notice the huge advantage in midrange power the 13B-REW has over the Renesis. It doesn't need to turn another 1,000 rpm, and it's still going to be faster.

Peak numbers are great for selling cars, but they don't tell the whole story. You have to look at power over the entire rpm range.

 

JIM,

why dont you compare without the turbo? compare a n/a 91 to the renesis. I'm sure when my rx8 is supercharged the graphs will be in the Rx8's favor. If you compare n/a to NA you will see that the renesis is a far superior engine. PERIOD.

Also, the rx-8's powerband is not peaky like the S2000's. Torque curve is flat and it the HP pulls progressivily not in a peaky fashion. I dont think you have driven one. Yea I took you off ignore for this thread.


Also, Mazda can add more displacement to the renesis by using thinner side housings, its been discussed.

 

Have you ever heard anybody refer to a 4-cylinder (piston) car/truck as a 4 banger?

well... that terminology dosen't apply to the the rotary, therefore Zerobanger.

 

That, and ZeroCarKnowledge was already taken...

 

Jim,

I dont want to fight with you on this forum. I'm not attacking you. I asked you a question and hoped you can respond to it without the insults. If you want to be an adult and discuss this, cool. If you want to resort to name calling and immature acts be my guest. I'll put you on ignore perminently. Let me know, like I said I dont have a desire to name call.

 

A little searching will get you the answer to this question. It has been discussed ad nauseum.