944S with a turbo???

[Phil1000]

I heard of somebody putting a turbo on a 16V engine. I thought that the compression ratio of those engines was too high to put a turbo.

What do you guys think?

Philippe.

[mike944]

Anything can be done given enough time and money........

Seriously, I am very interested in this subject, because i have a 968 (very, very similar to an S2 engine) and i'm considering putting a turbo on it.

Yes, compression is very high, and without changing it, boost would be limited to a few psi at the most. There are 2 ways to change the compression. The factory used the 944 turbo single cam head on the 968 turbo (they only made a few) This turned the engine back into an 8 valve engine. I think the head should bolt right on, but i'm not sure.

The other way is to replace the pistons. This is a much better idea, since piston design is somewhat different on turbo pistons anyway, particularly in the ring land area. Somebody (i can't remember who) makes a set of turbo pistons for the 968, which has the same bore size as a 944S2, therefore they should fit. I can't remember who, but they advertise in Panorama. Powerhaus racing also sells a set, although they both might be reselling the same set.

I see you have an S, you could probably do the head swap, but you would likely have to have custom pistons made to go that route, since i think the S has 100mm bore and the S2/968 has a 104mm bore

[Porsche-O-Phile]

You could also simply change the pistons to 951 8.0:1 c/r ones. The advantage of the 16v head is flow, not compression.

I'm not sure how the "S" valves would hold up though over time.

[Z-man]

When the factory produced the rare and all-powerful 968 Turbo, they used the 8-valve head off a 951, instead of using the 16-valve head of the 968. Thus, Porsche never made a 16-valve 4-cyl turbo engine.

If the factory didn't, that's gotta mean something...

-Z.

[mike944]

In my opinion, I think the factory went the 951 head route so they didn't have to redesign internal engine parts. It was a bolt-on swap. I think they did it for economy not because it couldn't be done.

In the 968 community, there are quite a number of people who have created 16V turbos, and they are extraordinarly powerful. Some have well over 400hp at the wheels! Much more than the factory 968 turbo.

[bader4]

The 951 or S head will not interchange onto the 3.0 liter engine. The 951 head the factory used on the 968 was modified to fit the 3.0 block.

[Phil1000]

The 2.5L turbo piston swap with the 16V engine has some potential. From my point of view the 16V head should be stronger than the 8V head because the compression ratio is higher and it's the compression ratio that is hard on valves not turbo boost, but it's only my way of seeing things.

Then there are still a few things to figure out, is the exhaust manifold from the turbo compatible with the 16V head and is the 16V intake manifold compatible with the turbo setup. After that there is the engine management, I don't think that a standard EPROM is going to do the job I would probably have to get a custom EPROM.

I'm going to look into it a little bit more and ask questions around but your input was very helpful, if anybody has more I will be happy to read it.

Philippe.