Clive's 400 BHP Super GT RX-8 Race Car

[zeppelin101]

GT40 is huge for 400hp!

[clive]

GT40 is huge for 400hp!

Having used GT35\'s and GT42\'s on Rotarys in the past, I agree :Thumbs-up


However, its actualy being built for 550 because if it\'s built for 400 tops it would be tough to turn the wick up, much easier to turn it down with the option of more if needed :burnout

Plus i\'m hoping for it to be transmission friendly (ish)

[Grant Monkhouse]

Having used GT35\'s and GT42\'s on Rotarys in the past, I agree :Thumbs-up


However, its actualy being built for 550 because if it\'s built for 400 tops it would be tough to turn the wick up, much easier to turn it down with the option of more if needed :burnout

Plus i\'m hoping for it to be transmission friendly (ish)

Are you going to bolt the box to the chassis? Also put a steel sandwich plate in between the bottom of the inspection plate?

[Will66]

Will you be using the RX8 six speeder?

[Casey]

I can answer that one - "yes", as Clive very kindly sold me the spare 6 speed box he had bought as a racecar spare when mine gave out at Snetterton (the day after I changed to the "higher spec" Fuchs Syn5 "Racing" gearbox oil ).

He is pretty sure he will blow one at some stage and wanted a spare available. With the number of 8\'s being broken there are plenty of cheap 2nd hand boxes around it doesn\'t seem to make sense to repair one, easier to replace and scrap the blown one......

[Will66]

Aha, interesting.

[zeppelin101]

Plus i\'m hoping for it to be transmission friendly (ish)

Depends rather on the torque output and shock load.

From memory, RX8 boxes share similar (if not the same) internals to an S15 box which seem to start popping at ~350lbft torque.

[clive]

Depends rather on the torque output and shock load.

When the RX-8 first came out it was said that the box was very fragile, however it would seem from Drag Racing in FD\'s where there\'s much more drama for the gear box going on that they are not that bad, so fingers crossed.

Also worth knowing that I\'m trying to put together a simple "affordable" race car so others may be able to follow .

[HaywardRotary]

GT 40/94 is really great turbo for circuit.
Full boost will be 4000 rpm.
Max revs 9500.
1bar boost = just over 500 hp flywheel.

[Grant Monkhouse]

What port work? Major extend port?

[Will66]

The RX8 box is an Aisin box, the AZ6, which I think was fitted to the S2000, the S15, the Lexus IS200 and the mk II Mazda MX5 with Six Speed Boxes.  Toyota wouldn\'t fit it to the IS300 because they felt it wouldn\'t cope with the 218lb ft of torque from the 2JZ-GE motor.
 
However Chris Impey used to run an RX8 box on his drag car before going for a half tub and a Lenco 5 speed air shifter.  I think it ran into the 9s on it.  So it\'s not a chocolate affair.  The series 1 box does seem to be a lot tougher than the series 2 box (the R3) which came from the Mx5, the synchros on that seems to be made of spit and kleenex.  Personally I reckon that the MX5 box isn\'t up to a 9000 rpm input shaft and Mazda tried to save money fitting it to the RX8.

[shaunwil]

If you look between me and Chris I haven\'t damaged an FD box with the GT3574R and Chris has lunched a few FD boxes with the GT40. Not sure if mines more progressive on boost earlier. The dyno graph is very straight in torque.

Shaun

[Grant Monkhouse]

If you look between me and Chris I haven\'t damaged an FD box with the GT3574R and Chris has lunched a few FD boxes with the GT40. Not sure if mines more progressive on boost earlier. The dyno graph is very straight in torque.

Shaun

Maybe your not giving it enough abuse? Have you bolted the box to your chassis?

[shaunwil]

Box isn\'t bolted to the chassis  with a brace but there are quite a few under body braces.

Shaun

[zeppelin101]

If you look between me and Chris I haven\'t damaged an FD box with the GT3574R and Chris has lunched a few FD boxes with the GT40. Not sure if mines more progressive on boost earlier. The dyno graph is very straight in torque.

Shaun

I don\'t understand what you\'re saying.

The car with the smaller turbo hasn\'t lunched as many boxes as the car with the bigger turbo?

Surely that\'s elementary as the car with the larger turbo will more than likely generate more instantaneous torque through the drivetrain and smash it to hell.

Anyway. Provided there is a fairly progressive torque curve and you have an element of mechanical sympathy you should be able to push the box beyond it\'s design limit for a while at least. Same with most mechanical devices, it\'ll just have a drastically reduced life span.