Mark944na86

The 3.0L turbo route usually seems to be the result of adding a 3.0L engine to a 951, rather than adding turbo plumbing etc to an S2. I can imagine why this might be, but was wondering if anyone has done it the other way, i.e. adding the plumbing etc to an S2.

One reason to do this is that you can get ABS more straightforwardly this way, for example, but I was wondering if there are any hidden "gotchas" to this approach? Any additional heat shielding needed compared to an S2, or are there mounting points that have to be added?

Just curious. Every now and then I start thinking about what it would take to turbo an S2.

User 52121

I think the "3.0L Turbo" route is typically either a bored/stroked 2.5L, or a 3.0L S2/968 block but with a 2.7L SOHC head.

Though I think there are a couple guys running 3.0L 16v motors, I don't think that's the norm (among the 3.0 guys.) I think most of them are 8v motors.

elargentino

Well, actually the 3 liter route is usually the 3 liter block with the 89 2.7 liter 2 valve head (like the factory 968 turbos), or, if you are a millionaire, you may properly prepare a 4 valve S2 or 968 head for the 3 liter block.

Of course the 2.5 turbo head does not "fit" the siamesed 3 liter block without front coolant jacket modification.

In my opinion, the way to do it, is like the factory.
Use the 2 valve head and take advantage of all the natural gifts of the 944 series engines....TORQUE.
To spin these engines high and try to squeeze big top end out of them is to defeat the purpose.
OTOH....very few machines can match a 3 liter 2 valve 944968 series engine that makes big boost early in the rev range....

MooreBoost

https://rennlist.com/forums/944-turb...atio-calc.html

MooreBoost

found a better thread
https://rennlist.com/forums/944-turb...bo-the-s2.html

Relaxed90

Stock compression on a 3.0 S2 motor is too high. It can be boosted, but it would be a chore to control knocking at such a high compression to start with before adding boost. I'm not sure what pressure the supercharger kits for the S2 put out, but I remember them being no more than 4psi.

If you want big boost like on 951's with the 3.0 displacement, first thing is to replace the pistons to drop the CR. It'll be a very expensive build - maybe more expensive than the traditional 3.0/2.7head build.

V2Rocket

i would love, with some nice fuel (e85?) to take standard 944 turbo gear (k/26, ic) and modify the manifold etc to an S2 and just run it at like 10 or 11 lbs boost like a 951. it would make good power and likely have almost no lag...may be worthwhile to use a k26/8 for top end because the displacement might choke on a #6...

anyone think it'd be doable to run an S2 motor on a 951 computer?

Mark944na86

Thanks for the thread pointers -- interesting reading!

Just to be clear, I wasn't referring to the process of building 3.0L turbo engine from a 951 engine when I was talking about starting with a 951, but rather starting with a 951 body rather than an S2 body.

I'm thinking about the mundane but necessary stuff before you even think about how to modify the engine -- e.g., fitting a crossover pipe, mounting a turbo, BOV etc. Plumbing. How hard is it to add all the 951 exhaust plumbing to an S2? Any additional heat shielding required in the engine bay, for example?

To keep it as simple as possible, assume using a 2.7L 8V head on a S2 block (i.e, stock 951 intake and exhaust manifolds bolt right up)... Is all the 951 turbo plumbing a straightforward installation on an S2, or are there any non-obvious differences to consider?

elargentino

The software is the easy part.
It is easy to run an S2 on a 951 DME - with a custom chip. You can even retain the flywheel/pp.
The difficulty lies in the mechanics.
It is not justifiable to use the stock pistons, etc because of the expense.
You cannot simply bolt on this head, either.
You will float the valves with any positive pressure whatsoever, because of the springs. This is just the beginning.
Obviously, you need turbo exhaust valves, etc., etc.
Also - you now will double the amount of everything, associated with the cylinder head.
And don't forget about both intake AND exhaust manifolds - you'll not be requiring mild steel for that ex. manifold, either. Let's get a price on just a Burns 4-1 321 merge collector - nothing like that price to give you a coronary infarction.
Sounds like I am making a mountain out of a molehill?
I am not.

V2Rocket

are the springs of the 16v head really that weak?

MooreBoost

i think with low boost the stock valvetrain is doable. but if u plan on running high boost then an upgraded head is a must. like in the other threads the only hard part is the manifolds

elargentino

This is not even a consideration - apples to watermelons.
They are not strong enough for a turbo application.
It is not worth the risk in an engine where any parts say "Porsche" on them.

333pg333

Here's one that's just about to come out of the oven:

https://rennlist.com/forums/944-turb...-together.html

Raceboy

Have you done a 16v turbo conversion yourself?

Markus951's 3.0 16v turbo engine had stock valve springs, stock 968 pistons and 951 rods, with thicker MLS head gasket and GT3582R it made nearly 500 rwhp.
Ran fine until Duke bought it and had serious overboost (something like 30 psi?) and piston ended up being in wrong orientation.

Bottom line is that there's nothing wrong boosting a 16v, in fact Porsches 1st (and successful) attempt was 2.5l 16v on 924 GTP Le Mans in 1981.

mikey_audiogeek

that's one way of putting it...