930 engine and Trans going into an sc. What do I need to know?

[Ronnie's.930]

Originally Posted by Bob Kontak

I would just be scared with the 930 motor/915 gear box set up to give it the beans with no speed built up.

As Brandon just noted, that is exactly the problem with running the 930 engine-915 gearbox combo . . . the "fun" of owning/driving a turbo powered 911 is mainly in "giving it the beans" - nothing quite like it (as Brandon also said).

PS - thanks for preparing yer sister so well!

[Bob Kontak]

Originally Posted by quattrorunner

Flame on.

Great post.

Drove a 930 once and my raisens shrunk to the size of bb's.

[Ronnie's.930]

Originally Posted by dzlndan

I would love to hear more on this idea. Not to hijack or side track this thread, but is there any recommended threads on this?(more stout modded 915). I'm boosting a 3.0 (I know I'm crazy) but I need to break open my gearbox anywho because of syncros and I don't wanna go thru what this poor guy is going to go thru. I had the same thoughts on trying to locate a 4sp but now not sure that's the best idea.

I can't point you to any 915 build threads, but when you say "boosting a 3.0" are you talking about turbocharging an otherwise stock 3.0 engine (mainly talking stock compression ratio)? If so, you'll be limited to around 5psi of boost, and while that will add a nice bump in horsepower, it will not come close to the hp, and primarily the torque, of a tuned 930 engine, so in other words, you will likely not have a problem using a suitable 915.

[WERK I]

"You're going to need a bigger boat."-Roy Scheider "Jaws"


Seriously, you're also going to have to update your brakes. You're doubling torque, you should double you're stopping power. The transmission mount is different than the 915. You'll have to search for one of those. Torsion bars, especially the rear, will have to be stiffened a bit. You are going to see a lot of squat when you get on it.

We use to advise turbocharging a 911 is a more expensive proposition than buying a 930, but now that no longer holds true.
Good luck....it should be a blast.

P.S. 930 engines used dual fuel pumps- one by the fuel tank, the other by the rear axle.

[quattrorunner]

It doesn't have to be crazy expensive. Swapping the gearbox is starting to seem more complicated than the engine conversion.
As far as torsion bars I never really had problems with my suspension not being up to the task. Brakes are another matter.

[TRE Cup]

We have built just about every conceivable combination of turbo conversions over the years. The most fun combo has been the 77-86 915 with a billet side cover / 930 diff bearing , and a lightly built 3.3 (about 400 hp)
The car is a blast to drive on street, mountains, or track. BUT track use did bring up the limitations of the gear box. It just will not last with all that torque going through it. You can mitigate the problem slightly with adding a pump and cooler to lower the oil temps, use the best lubrication changing it often, REM treatment to reduce friction. BUT at the end of the day it is still limited.
An interesting observation: At one time we had two identical 3.3 turbo powered cars in the shop; one was a four speed 930 box and the other a 5 speed 915. We just had to find out right? The 915 felt really quick, but guess what? The 4 speed matched the acceleration up to about 125 mph.
No question that the 915 was more entertaining to drive, and in the twisties would be a definite advantage over the slow spool up with the 4 speed.

So that is my two cents ;-)

[Ronnie's.930]

Originally Posted by TRE Cup

The 915 felt really quick, but guess what? The 4 speed matched the acceleration up to about 125 mph.

Brandon, did you read that ^^^?

I know yer past those concerns, but still, should be music to your ears (eyes)!

[quattrorunner]

Indeed!! That's great news.
That's great I've been waiting for someone that knew both. Cool info. I was expecting a slower car.

[quattrorunner]

Originally Posted by TRE Cup

The 4 speed matched the acceleration up to about 125 mph.


So that is my two cents ;-)

What happened after 125?

[Ronnie's.930]

Originally Posted by quattrorunner

What happened after 125?

I think he was implying that was as fast as they were willing to go on a public road.

[quattrorunner]

uhuh.......Sooooooo, what happened after 125?

[Ronnie's.930]

^^^ With the 930 gearbox, 125mph would be about 4-4.3K RPM in 4th gear = a VERY sweet spot for most turbochargers = WARP SPEED duuuuudddddeeeeeeeeee!!!!!!!!!

[rattlsnak]

I ran a mildly built C2Turbo engine (@350hp) with a bone stock 915 in my SC for 4-5 years with HARD track days in that mix. Never had an issue. The guy after me drove it hard for a few more years and the guy who owns it now floggs it routinely. Still going strong.

After I sold that car, I built a lightweight '72 with a 993 3.6 in it and it was very disappointing. I mean it was fast and quick and all of that, but it simply didn't hold a candle to the boost factor.

[Mr9146]

Matt mentioned it already but the gearbox is too long and the axles won't work. Find a 75-77 930 trans and it will fit fine. Or, use a 915.

Funny that nobody here mentioned the second fuel pump.

There are also the wiring differences, the oil system differences, the sway bar fitment issues (with the 930 trans), the tranny mount issues, etc. ... and if you use the 915 then you have clutch/flywheel issues to deal with.

It's not a plug and play...but it can be done. We've done it many times and I'm in the middle of doing the conversion to my own car now ... 3.4L non-intercooled with a 915 in a 75 Carrera.

[T77911S]

Originally Posted by vintagecarlover

got the deal on this package. cant buy 3.6 for what i paid for both including boost guage, shifter and shift rod and out put shafts

sell it and make a little $$$ and buy a 3.6

[javadog]

Originally Posted by Mr9146

Funny that nobody here mentioned the second fuel pump.

It got mentioned, you just didn't see it. One thought on that is, whatever he does, he doesn't want to wire the fuel pump circuit like Porsche did. It's a weak point on turbos.

JR

[quattrorunner]

All the smart people say two pumps. I'm running 1 044 pump. I'm sure I'll need another with raised boost.

[vintagecarlover]

okay then wouldnt it make financial sense to go to coil overs, ditch the torsion tube and install the 930 trans? selling the 915 should pay for some or most of the coil over costs right?