3.2 low pressure turbo - data point

[puddy]

Originally Posted by quattrorunner

I suspect it's a crapshoot. Both mine broke second gears in similar ways, coming smoothly on boost. was running .8bar boost.
That being said I'm jealous of those who still have 915 ratios.......

Was your 2nd gear a strong Guard version? I fear of this day coming, when something breaks and the car is down for a period of time. But I also really don't want to convert to a heavier G50 and related hydraulic components.

[quattrorunner]

Originally Posted by puddy

Was your 2nd gear a strong Guard version? I fear of this day coming, when something breaks and the car is down for a period of time. But I also really don't want to convert to a heavier G50 and related hydraulic components.

No it wasn’t. I know that would give more strength but even he said the width doesn’t change. Only the “freshness” of the temper. His gears would certainly help but they’re not cheap. Againbit cane down to money for me. I figured that to make my 915 strong enough for comfort it would cost me about $10k. And then I still couldn’t trust the gears completely. So I bought a short 930 and threw it in. Now I just need more power.

[IROC 912]

Originally Posted by quattrorunner

I figured that to make my 915 strong enough for comfort it would cost me about $10k. And then I still couldn’t trust the gears completely.

What are your opinions on a 930 gearbox, but with shorter R&P ? Assuming you have the stock R&P now ?

I usually start off from a light in 2nd gear anyways as first gear is useless ... so i'm driving a 4 speed the majority of the time

Cheers,

Sandeep

[quattrorunner]

I love my 930! till I want to go faster than 130mph in mexico. I love having the tall gear but also hate that it's so tall and my only option. I'll be fine once I get a new clutch and raise my boost.
I think the shorter r/p is great for the track and canyons but I need to get there on the freeway....
Currently with .5bar boost I struggle going faster than 130-140mph. 1-3 gears is great. Again, my problem will largely be solved with 400hp+ that 1.2 bar boost will give me.

[TurboKraft]

I would bet that by the time you rebuild and reinforce that 915 transmission (bearing plate, machining, side cover plate, etc) you'll be more than the cost of shortening and rebuilding the G50.
Especially if you start adding gears to the 915.

More power will probably require a stronger 915 clutch, the G50 needs a clutch... probably similar monies there.

The G50 uses an altogether different shifter, so you'll need a good used one from 1987-89 Carrera.
Same goes for the pedals.
Yes, they're getting hard to find and they are pricey, and that's before you add a $600 Wevo shift lever of $300 coupler.

The factory hydraulics are so reliable, I don't think there's any reason to entertain using any other clutch release setup.

[IROC 912]

Originally Posted by TurboKraft

I would bet that by the time you rebuild and reinforce that 915 transmission (bearing plate, machining, side cover plate, etc) you'll be more than the cost of shortening and rebuilding the G50.
Especially if you start adding gears to the 915.

That's what I was thinking ... only issue for me is I don't think there is anyone local to take this project on, so that means shipping the gearbox to the States. I have to put a pricetag on the shipping label for the courier and get charged the sales tax on my own gearbox

It all comes down to $$ at the end of the day and its looking like the best option may be to put the money into the G50.

Cheers,

Sandeep

[puddy]

Sandeep I know a local guy who may be able to help with shortening the trans. PM sent.

[TurboKraft]

Look at photos of ones that have been shortened, you'll see how much needs to be removed from the bell housing and the input shaft.
Don't forget to shift the profile inside the bell housing by the same amount so you have clutch clearance.
Re-heat treating the mainshaft is a good idea, too.

Hope your G50 is in better shape than the ones we've been seeing lately -- bad 4-way bearings, bad sliders... $$$$

[IROC 912]

Originally Posted by TurboKraft

Look at photos of ones that have been shortened, you'll see how much needs to be removed from the bell housing and the input shaft.
Don't forget to shift the profile inside the bell housing by the same amount so you have clutch clearance.
Re-heat treating the mainshaft is a good idea, too.

Hope your G50 is in better shape than the ones we've been seeing lately -- bad 4-way bearings, bad sliders... $$$$

Agreed. I'll spend a few $$ to open up the G50 anyways to see what I am working with.

Cheers,

Sandeep

[IROC 912]

Hi All,

I'm looking to make some changes to my setup in the next few weeks and was considering a turbo upgrade. I will still be using the 930 euro heat exchangers and a zork tube for the exhaust, while still keeping the system at about 7psi intercooled. I am still working with the 915 gearbox that's in the car now, while rethinking my approach with the G50 ... getting more certain that it will not be happening and best is to stay with the 915.

What would make to most sense for my low pressure setup ? keep the GT30R and upgrade the hot side up from a 0.63 AR to a 0.82AR ? Or get into a GT35R with 0.82 hotside ? Or something else ?

The car is mostly a weekend warrior with lapping days and the goal is to decrease the intake temps and run more cool while on boost.

I usually run lapping days at local tracks and am able to hit 180 KPH at 6500RPM in 4th gear at these tracks. I'm at about 300 RWHP / 300 RWTQ right now and happy with the #'s but maybe there is more efficiency to be gained somewhere.

Cheers, for any input.

Sandeep

[quattrorunner]

Gt35r is larger. The gt30r is perfect for the level your at. Even gt28r might be great. Best is gt30r so you keep boost/torque higher in the rev range for 915 longevity.
I loved my 915 performance but your best to keep power level where your at if you keep it. 2 more lbs of boost and your in a dangerous power level for the 915. I went with a 930 gearbox after breaking two 915 gearboxes but I still miss the ratios of the 915.