can i take the 13bT from a second gen and attach a 6 speed from an rx8 to it?
would that work? by the way the 6 speed would run me about 875$ extra
where as the 13bt s5 comes with a 5 speed..so basically im paying 875$ for a 6th gear....
i know the rx8 has a renesis rotary which is a modified version of the 13b rotary we are used to but is it possible/ inexpensive/ logical( logical as in worth it...any acceleration gains? top speed gains?)

 

Firstly, that engine swap is not overly inexpensive.

I can only imagine that the rx8 tranny is not cheap either. I would not think its worth it.

IMO for the effort and readily available support I would be far more inclined just to use the TII tranny. That being said I am not even sure if the rx8's trannys bolt up to the FC engines or even fit in the tunnel on the FB's

I know a bunch of people have asked but i cannot recall the responses

 

thank you
i got this idea randomly while playing different setups and got a little over excited and then i thought to myself not worth it ....not worth that large amount of money for an extra gear that possibly wont bolt up

 

As well, the TII tranny would be sufficient once you have the power to get to those speeds (on a race track only obviously...)

I think alot of people have seriously considered it, but again i do not know whats involved. Probably because alot of us first genners are quite cheap.

 

It will bolt up. The RX-8 trannies are known to be somewhat weak, though. From what I understand you basically just get an extra gear between second and third. Not worth it IMO.

 

good to know though

 

what are the gear ratios? might not be a bad idea for a mildly powered 7 that does frequent highway cruising......... keep them RPMs down

 

One big problem with the RX-8 trans...even if it bolts up, there is no output for your speedo. The RX-8 uses a wheel speed sensor for the speedo, like many modern cars do.

So:
- it will bolt up
- 5th is basically like our 4th (1:1), no 2nd overdrive gear
- more $$$
- way weaker than TII tranny, also weaker than the NA 5pd tranny
- no speedo

Easy enough to find the ratios if you are still thinking about it, but basically you just gain an extra lower gear/closer ratios. Go for the TII tranny..strong, cheap, and plentiful replacements if you do break it.

 

That would actually hurt the MPG to keep the RPMs down while crusing on the freeway. Even in the FC's with the tall 5th gear, the RPMs are around 3k at freeway speeds. The rotary is more efficient while cruising in higher RPMs that piston motors. Hell my SA with a 4 speed got somewhere around 22-25mpg on the freeway even crusing at 4k at 65mph

 

shouldn't less RPM always be less fuel? assuming it's the same engine, or until you're down so low in the rpm that you can't maintain the speed you want to maintain. As long as you don't have to add throttle to maintain the speed, the lower rpm should always be less fuel.

 

the final drive ratio is the same, the extra gear isn't added to the end, it's added between 3rd and 4th The tops speed won't change at all and your acceleration won't be affected below like 90 mph so it is a waste of $875.

 

I don't know why, but it IS true that loer RPM is not as effient at hwy speed. you WILL use more gas crusing at lower RPM. I used to commute my '85 GSL over 200 miles daily. I would ALWAYS get better mpg if I was in 4th or speeding much higher than the legal limit in 5th. normal crusing in 5th was worse mpg.

Not looking to argue with any one But this has been my experiance. also driving with the lights up will noticably hurt mpg. and at top speed you can feel them going up like an air-brake.

 

See with a piston motor, it takes more fuel to run higher RPMs due to the reciprocating motion, while it takes less fuel to increase RPM in the rotary since it is already in the same motion, if that makes any sense at all. Although my girfriend's Kia Sephia is geared so damn short that it screams down the freeway(don't know what RPM cause it has no tach) and it get's pretty good mileage

 

it isnt setup like the domestic 6 speeds.

the rx8 box, is setup like the mazda race trans from the early 80's, with a granny 1st. so that means, all the gears are closer (which is great on the track), and the over drive is shorter, so it revs higher on the freeway.

there is no speedo gear, but we found a hot rod company that makes something that will work.

shifter is about 2" further forward, than the FB trans.

and the trans isnt really that durable.

 

It's simpler than that. It's just that our torque peaks higher. That's also why the Kia would be geared short.

 

Makes sense