3.2 Turbo Conversion Questions
 

Good day all,

First, I’d like to thank everyone for the informative posts! They’ve been very helpful this year!

Now the point of my post... I’m a bit compulsive sometimes and this weeks no different. I’ve just become the proud owner of a almost complete turbo setup. Intercooler and piping, exhaust from header to muffler, turbo and waste-gate.

I’m contemplating installing it on my freshly rebuilt ‘86 3.2 Euro spec. I’ve read as much as I could find on here. I’ve read many threads that say you need to reduce the cr, and 1-2 say it’ll be fine if you don’t go crazy.

Before sinking more money into something that won’t work I have a couple questions that I hope you will take the time to help me with.

I’m not looking for huge increase anywhere from 270-300 hp would be great! I want something I can continue to use as my daily driver, and track a couple times a year.

Will I blow up my engine if I keep the boost low? I’m thinking a smaller turbo hoping to have more impact throughout the entire power band.

What’s my best option for fuel and engine management? Is the motronic capable of delivering enough fuel and management with custom tuning?

If you have suggestions for reading I’d very much appreciate those links too. Any help is much appreciated!

spence88mph on here has done it and did not reduce compression from memory.
with modern engine management and low boost you won't have to reduce compression.
given you've just rebuilt the engine i wouldn't want to be going back in there to mess around again.
aftermarket ecu would be the way to go.

I dont have a 3.2, but a 3.0 with high compression. I run 10 lbs of boost, and have for the last 3 years or so. My motor is intercooled, and run Microsquirt EFI. I ran E85 for awhile, but am back on 93 for the time being. It is happy on either fuel at my current boost level. The most important thing is the ability to modify your ignition timing, you will need to retard the timing under tip in and boost. You will be fine, these are strong engines.

Scott, are you running a 915 on your car? I've probably asked before but I can't recall.

I've got a lil over a year to figure out if I go NA or succumb to Rawks evil whispers. ;)

That’s great to hear! I’m guessing it’s the 9.3:1 CR variant? Any thoughts on staying with motronic?

Normal compression is fine, if you keep the boost low. .5 bar will achieve your aims and be very driveable/fun. With a good IC .7 bar is fine.
Motronic works, but you'll need a turbo compatible chip-protomotive etc.
You'll also need a rising rate fpr or something similar.
Vems or something similar also works, and gives you the ability to change out injectors.

One thing's for sure - if you do decide to go NA, make sure that you never drive someone else's turbo powaaaahhhhhheeed 911 or you will bisch-slap yourself silly, and probably even kick yourself in the nutz (two times! :eek:) for choosing the weak sauce option!!!

Yes 915. Busted 2nd gear back a few years ago. When I put it back together, I added the CMS bearing retainer. I already had the beefed up diff cover. I’ve been beating on it pretty hard, and it’s holding up ok. I have a used transmission that I bought awhile ago in case I have another “explosion”. Check out the video I posted of my car.

Rawks, yea I know. I just think that if I go turbo on the Porsche that the costs will end up drowning me as I keep upping the boost. Going NA is a way to keep me from doing dumb things.

Figure I can get an older Scooby or EVO that will make all the turbo power and sound for a fraction of the P-car tax. ;)

We'll see, I still have that 3.2 intake for the SC in case I fall to the dark side

Is the 3.2 intake conducive to turbo charging?

Yes, very.
The turbo pancake manifold can make good power but not as much as the 3.2 manifold, but it needs efi to work. Can't use the 3.2 and keep cis easily. Efi is better anyway. Your car will love a turbo.

Yea, I bout a 3.2 intake and TB, to replace my PMO carbs with the intention of turboing my car... still on the fence though as I know it will lead to a landslide of $$$$

For the price of making my Porsche faster I can buy a whole other car that is faster, and still have my Porsche... P-car tax can be brutal.

I think the biggest issue is the 915 trans... unless I get good at rebuilding them I don't see an easy fix lol. 930 SBH are not cheap.

If you're gentle with the trans, it'll last quite a while. If slamming 1-2 shifts is your thing, no so much. For a car that see's track use, I could see the 915 as a liability, on a street car not so much.

😁👍

Great to know. Is a G50 swap the remedy for this or can you switch internals to 930 4sp?

915 really isn’t meant to take the turbo torque. It’s a great ratio gearbox but won’t last.
The 930 can. But those gears won’t work/fit in a 915
The g50 is a completely different box.
G50 and 930 can fit but both need to be $hortened up to fit.

If you're only aiming for 300 wheel the 915 will hold together, have some mechanical sympathy, lots of bigger HP NA engines with more power than that running around. Go a small turbo like a GT30 and you'll get there very easily if you have the time to mess around.

Many people have broken 915 boxes with engines producing hp and torque in the 300 range (including Brandon, two times :eek:). The 915s that hold up are a fluke and/or the owners are dainty with the throttle (no sudden bursts of acceleration), which is hardly the point of building a blown 911 engine.

The high hp, n/a engines have nowhere near the torque of a boosted engine, so are easier on the 915.

Matt Monson posted side by side pics of 915 v 930 gears, the 915's are far more narrow/skinny - easy to see why they aren't up to the task.

Geronimo, how are you still debating joining the dark side? I thought we settled that in a previous thread. I've now got 100 miles of testing and tuning on my turbo conversion, and it's an absolute riot. It's effortlessly making 175 kpa, which is actually a problem since I'm still sorting out the settings for the boost controller.

The 3.2 intake is conducive to EFI conversion because it comes from an EFI setup. It is more efficient than the 930 pancake manifold, so is a good upgrade along the way. In and of itself, I would say the 3.2 intake is actually less conducive to a turbo conversion because it takes up more of the already limited space in the engine bay and none of your original system will mount to it without custom fabrication. With that said, I would recommend the swap anyway.

To the original question: a turbo setup with an intercooler should be fine on the current engine build for the power level you're looking at. The real issue is engine management. I don't know if there are turbo chips floating around anymore. I'm pretty sure the protomotive chip hasn't been a thing for some years now.

I’ve read this many times over the years. What’s the solution for factory 915 cars then? I’ve heard even a rebuilt/strengthened 915 won’t last and early 930 gearboxes are not cheap or easy to find to swap in.