964 twin turbo convertion
 

I got a call from a friend a few days ago. He wanted me to take a look at his long time project. He's building a 90% track/10% street car. Currently without an engine.

He has a completely disassembled 3.6, which has been laying around for years, collecting dust. One head is missing, cams look tired, crank likewise (maybe just dust), no DME and a bunch of other stuff is missing.

But on the table was 2 sparkling new Garret Turbos and an intercooler......so that got me thinking.

I've rebuilt a few engines. A 3.2SS, a standard 3.2 and another 3.0. No experience with turbos. So still very much a rookie. But I can read a book, and learn from the experts - hence this post :D

First: Any recommendations on literature on the subject?

Second: I first thought we should do a 3.8 with EFI/ITB (which is within budget). But maybe we could go Turbo for the same cost? 0.8Bar boost with new pistons with CR 8.5:1, VEMS (or MS) engine management, wastegate, springs, tubes, oiling etc seems no too expensive compared to a 3.8 ITB/EFI? Or am I wrong?

He would like +350hp, mostly for track use. But car has to commute to and from the track.

You’re going to have a really hard time capping hp at 350 on a 3.6 at 0.8 bar of boost, as long as the twins are big enough and the IC maintains temps.

You’ll never ever remotely make the same power out of a 3.8 with ITB’s NA over a boosted stock 3.6.

Any idea on the driveability of these conversions? If we keep the engine stock and install new pistons, aiming at a CR of 8.5:1. As mentioned, the car is 90% track, so driveability and longlivety is essential.

drivability will be determined by the same factors as an NA car (weight of rotating assembly, clutch engagement, tune, etc) as well as the size of the turbos, the displacement and compression of the engine, cam profile, and boost management strategy. boost management can be done with your engine management if you choose, with a stand-alone electronic boost controller, a manual boost controller, or simply the wastegate. there are pros/cons to all of them.

longevity is going to be determined largely by how hard you push the whole package and temperature control. low boost and excellent temp control will net you a healthy motor for much longer than a high-strung, very hot motor.

i reckon you've got a lot of reading in front of you before a final decision is made. good luck and keep us looped in. sounds like the beginnings of a great project.

Driveability is all in the tune. Poor tune, poor driveability.