As the block comes with an fd trans, I will probably try the Rx8 5 spd bell housing and tailshaft and fd gears combo. Might as well be safe as those transmissions are arguably proven to handle more power. These Rx8 5spds seem hard to find.

On another note, im torn as to buying a ported throttle body. I feel as tho that might be unnecessary.

Lastly, any recommendations on dremmel heads to use for porting the iron and side housings?

 

Well the R15M-D is also used in the Ford Ranger and a couple of other trucks as well, do you think that they also have the same ratios and gears? In post #15(if you read it) I posted the differences in gear ratios between the 3transmissions. Also just because something has the same ratio doesn't mean it's the same part. Now if you can find that they have the same part number, then I'll agree for those same 3gears in the 2transmissions. The rx8 5speed transmission is found on the low power rx8 with 192hp in the rest of the world, here most people with the low power end up with broken transmissions and switch over to the 6speed. Lastly only the shaft for the shifter needs either to be switched from the rx8 5sp unit, or the rx7 fd has to be shortened.

 

I'll let u all know how my 6sp goes with 500hp. I drive hard but not planning to do many 1/4miles, just drifting.

 

I predict that the first or second time you give it a good clutch kick in 3rd or 4th gear entry it shears all the teeth off. lol sorry buddy.

 

Please do keep us updated. I'm very interested to see the strength of the 6spd. I figure we need more experience and experimentation in that department.

 

I doubt he'll even need to clutch kick it, just going through all the rpm' sand gears will do it...

 

As mentioned earlier , I found out that all the major part nos are the same between the RX8 5speed and the Rx7 box . It makes no sense whatsoever that Mazda would change the design of any of the components inside the box when going from a higher powered RX7 to the Rx8 . They already had the gearbox in their parts arsenal ... all they had to do was mate it to an RX8. They wouldn't go and spend money just to make it weaker ......... would they ?
Your comment about the RX8 boxes breaking ............. Are you sure they are not just failing in the sense that the syncros crap out and they start graunching gears ? Mine graunches into reverse , 2nd and 5th to varing degrees and has since I installed it (second hand)2 years ago. But .......... it isn't broken !

 

It's a technique that has its time and place. If what you're saying is true then none of the formula D guys with 1000+ WHP builds would clutch kick every once in awhile.

 

I'm not sure why he is being so pig headed about it. I had both apart on the bench on Friday. ... if anything the RX8 tranny should be stronger as the tailshaft has much beefier ribs on it. I had aT11 bellhousing as well. I'm with Brett... why would they make a weaker transmission they already had in the box from the FD

 

It won't. .. mine lasted 10 minutes @ a detuned 425 whp ;-)

 

So are u guys saying the 6sp isn't as strong as the 5sp? Both rx8 of course

 

That's exactly what everyone has said

 

So the rx8 6sp has completely diff internals to rx8 5sp?
Wow, I wouldn't have thought so.

 

I'm not being pig headed, if the part numbers are the same, then they are the same, no problem from me! But what about the gear ratios that are not the same, what are those from?

 

What? I was saying with that kind of power it'll break on it's on with no abuse from clutch kicking it.

 

This just in!

 

Sorry to bring up the topic once again, but in the case of using the fd transmission with the 5spd rx8 bellhousing & input shaft, this setup would require an rx8 clutch assembly, not an rx7s correct?

 

The clutch i bought was the same for rx7 or 8.

 

If you use RX8 or T2 bellowing clutch is same....if you use FD bell you need FD pull type clutch

 

I am just where you were about a month ago. Just some pointers while you pull the engine apart. Make sure you have a torch or something similar to help free up some stuck parts, and you'll probably need a impact gun with some torque. I had to use a torch and hammer to get my flywheel off. I had to buy a 1000 lb ft 3/4 impact gun from harbor freight to get the front pulley bolt out (My 500 ft lb 1/2 inch was not enough) Also, while separating the transmission from the block, make sure you read up on how to push the releasing washer from the inspection plate. If I read these tips prior to my adventure, it would have saved me a few hours of frustration.

 

Haha yup ok with the dismantling and that flywheel bout is where I am now. Just ordered the socket after running around and not finding it.

 

Well I have exhausted opinions from others so now I will turn to you guys and see if I can get some opinions. First off, I am thinking about getting a BorgWarner S300SX3-66 turbo with .91 a/r. First and foremost, will that a/r be large enough for high end flow? I was hoping to put the redline at 9k. I also heard the HKS turbo manifold bolts up to the turbo. Would that fit in the Rx8 bay without touching anything? Thanks again guys.

 

What are your horsepower goals? I don't know that turbo at all, but if you are not pushing it past its hp rating then the waste gate should be opening and allowing considerable flow out also.

If that is the case i think it would depend on the waste gate size.

 

Hks manifold will fit with small turbos like t04e

If you want the s366 youll have to make a custom manifold

 

Well first off, my guess is that the S366 will not fit with the HKS manifold. It's a pretty big turbo, it's got the same wheel sizes as my EFR 9180, and the 9180 is physically almost as big as a GTX4294r... the S366 might be a little smaller than the EFR9180 but not by much.

This is a pretty serious turbo, we can give you great suggestions on turbos, we just need some information. How much power do you want, how important is spool and response, and what is your budget for the turbo? I mean the S366 with proper setup and E85 will do about 600WHP all in with a big turbine housing. You'll already be over the 500WHP mark by about 18 to 20PSI depending on porting. That .91 housing is a little on the small side and you might even see it choke out at high RPM. I would aim for something around 1.0 to 1.10 range.

About the 9000RPM redline thing, just give that idea up right now. You don't need it and it's dangerous, you'll be making boatloads of torque down lower anyways. Stock redline is 8000RPM and most big power guys pull to maybe 7500 to 7800 unless it's a drag racing application.