WRX Gearbox Limits

ScoobieWRX · Post by **ScoobieWRX** » Sun Dec 30, 2007 9:25 pm

The WRX 5 spd is only good for 330lb/ft torque so clearly the 6spd is a big improvement on the old.

Good luck on this project...i read the on-going saga with interest

duncan · Post by **duncan** » Sun Dec 30, 2007 9:32 pm

ScoobieWRX wrote:The WRX 5 spd is only good for 330lb/ft torque so clearly the 6spd is a big improvement on the old.

Good luck on this project...i read the on-going saga with interest

Where did you get that info from on the 5 speed - that cant be right.

ScoobieWRX · Post by **ScoobieWRX** » Sun Dec 30, 2007 9:34 pm

My local Scooby dealership and TSL Motorsport both said the same. 330lb/ft

duncan · Post by **duncan** » Sun Dec 30, 2007 9:52 pm

ScoobieWRX wrote:My local Scooby dealership and TSL Motorsport both said the same. 330lb/ft

It seems very low. 1.1 bar on the std turbo must reach that level ?

ScoobieWRX · Post by **ScoobieWRX** » Sun Dec 30, 2007 10:07 pm

c. 16psi on a standard WRX TD04 wont get that. You would need to at least 18psi and then you're not far off so long as you have done all the other good things like full SS decat exhaust/uppipe, change the injectors (STi Pinks or better), high pressure fuel pump and regulator set up to about 3.5 - 4.0 bar and mapping to match.

Then you might just hit 330 - 340bhp which should also be giving about 320-330 lb/ft torque. In which case i would seriously be thinking about changing gearbox internals, although i hear the LSD on the back is very strong so probably wouldn't need sorting yet.

16psi TD04 on a std WRX should be good for about 250lb/ft torque. I'm boosting 16.5 psi tops with few mods like the decat uppipe but my 330cc injectors will be maxing out at around 270-280bhp with std pump. I'm probably doing a bit better than 250lb/ft but miles off the magic 330lb/ft.

duncan · Post by **duncan** » Sun Dec 30, 2007 10:19 pm

Ah I keep forgetting yours is a 2.0 Francis. The 2.5 wrx must get to that level much easier, I really find it hard to believe that 330 lb/ft is the limit.

Isnt Andy F running a std wrx 5 speed in his spec C?

ScoobieWRX · Post by **ScoobieWRX** » Sun Dec 30, 2007 10:40 pm

I would love a 2.5 bottom end with all the forged goodies. If i can find a reasonable oil burner that will take home made biodiesel next year and i have enough money i will retire my Scooby and turn it into a project.

I have a dream........

On the AndyForrestPerformance website they do various conversions for the WRX however....

They recommend uprating engine and gearbox internals as well as clutch etc... for mods taking the car over 390bhp. On higher mileage WRX's the gearbox is likely to fail at this level hence the 330lb/ft mark for the gearbox is probably not far off the mark for changing internals. Although the 6spd is fairly bulletproof at high torques.

He recommends the PPG setups. I looked at the PPG site and they even do full synchro's for straight cut gears. It would seem unlikely then that his c.600bhp mean machine is running a std 5spd WRX box, although you never know

Gerry H · Post by **Gerry H** » Sun Dec 30, 2007 11:41 pm

Francis is right about the five speed boxes. Mine only lasted as long as it did because I apply mechanical sympathy. PPG is the way to go on five speeds. I wasn't aware that the six speed could take that much torque otherwise I may have considered that option.

The other thing that put me off the six speed is the awful changes on the Subaru boxes, so the fewer changes the better. By comparison, having had pax rides with JJ at Marham, the Skyline box seems so much smoother and more precise.

Lee, my twin plate came from Nengun in Japan, http://www.nengun.com
it took a while to arrive but the wait was worth the

ESL · Post by **ESL** » Mon Dec 31, 2007 1:31 am

Got 2 5 speeders sitting in the garage now that I've just stripped to find third gear demolished in both at 320 lbft. Doh.

ScoobieWRX · Post by **ScoobieWRX** » Mon Dec 31, 2007 1:44 am

Hi Gerry,

For the top end WRX conversions where Andy F recommends changing all the gearbox/engine internals he does say PPG internals or 6spd late STi gearbox and that's for the 390 - 450bhp conversion so i assume from that the 6spd box is fairly bulletproof upto c.500 torques as Duncan has said.

There is a chap on Pistonheads that owns Surrey Rolling Road, goes by the monika Vixpy1. He says there is a chap running c.500bhp on a completely standard STi, and has been doing so for a while.

Vixpy1 has had this guys car on his rolling road and verifies that is the correct BHP figure, therefore the gearbox must be pretty damn tough!!

Same as you Gerry i am amazed my gearbox has lasted as long as it has due to some of the full bore standing starts and abuse the box has dealt with from time to time over the las 3 years and it has done over 84K miles. Mechanical sympathy and Redline Heavy Shockproof is keeping my box going at the moment. I just hope it lasts long enough for me to retire it eventually. :lol: