Raceboy, I have a full standalone engine management at the moment a 4424 from EMS (Aussie guys), the compression drop in stage 2 is to 9.2:1 with a 3.00mm Cometic HG, I know there are a lot of folks saying this is a bandaid but a lot of people do it including Ruf and BMW tuners. Plus then I only plan to go to 10-11 psi then about the same static compression as 7 psi on a 10.9:1 at the moment.

Anything more then its a rod and piston change....but that wasnt the design goal for this conversion.

rgds
mike

 

Hehe, glad to hear you went the right way.
And btw, thicker headgasket mod works, Markus951 has 951 with 968 engine and he uses thicker HG, GT35R turbo, standalone and basically stock engine produces 495 rwhp @ 1,3bar boost. So far very reliabliy.

 

Raceboy thanks didnt know that, , I am aware that the 968 has potentially forged rods/pistons vs cast on the 944S2, so that is why I am cautious about how much power I go for.
Once I fit the 3.00m H/G there is no reason that I cant boost up to 12-13+psi, about 450fwhp in my calculations, but I am very concerned about the S2 cast rod/piston combo, havent seen anyone do it so far...

rgds
mike

 

Markus951 used 951 rods.
S2 pistons have worked well on boosted application, Kert (nickname: cmf) has 3.0 8v with S2 pistons and 951 rods. Engine was boosted in excess of 1.5 bars (GT35R).

My bet is you'll be fine at 1 bar of boost eith lowered CR and properly set up engine managent

 

thats cool, my 60-1 HiFi turbo runs out of efficiency at 15psi anyway - its designed for low boost high flow unlike GT35s. So if I could run close to that I would far exceed my initial goals - thanks for the encouragement.

rgds
mike

 

Really nice example, me likes. Go for 951 rods.

 

Mike, thanks for posting your story and progress. I have done a lot of research on turbo-converting a 968 in the last few weeks. I came up with lots of information and apparently there are a few ways to go about the conversion. I was also aiming for modest power gains on a low-boost application, in the interest of keeping things simple, and inexpensive. In the end, I'm not a turbo fiend (I actually prefer NA) so if I ever find a route to get enough power (300+ crank) with natural aspiration, I'll do that. Not likely though.

I decided to keep the motronic, use 951 parts wherever possible, and definitely keep 16v variocam. I think the superior flow of the 16v head is such an advantage to start with, it would be foolish to revert to 8v. Although if the goal is modest power gains and low budget, the option of just sticking in a 951 engine should be considered too.

Luckily I have the forged rods (and pistons? cool) so I want to keep them, and work around them.

I was leaning away from using low-compression pistons, as they cost way too much. A thick headgasket seemed like the way to go. I didn't want to lower the compression too much, for fear of developing too much turbo lag, and it's OK if I can't use high boost. The 968 already has some lag, from the "dual-resonance intake manifold" and I hate it. I hate it. I want no lag at all so I look forward to a 951-style intake.

Anyway, hearing of your project and results is encouraging. I don't know when I'll dive into my project. If you have a chance, I'd love to see any detail shots you may have taken.

Thanks!

 

FRporscheman over the next few weeks I am going to do a few changes to the exhaust so when its apart I'll take some more detailed shots of the exhaust crossover, wastegate and also the inlet manifold. They are the main changes that can help you on your 968, the intercooler fitment to yours is totally different to mine.

If there is one piece of learning I can share, is the use of a standalone.
I looked at the motronic and burnng chips trying to play with MAF signals to compensate for larger injectors, all were bandaids (on 951 thats a different story) and as I got deeper into the work they got harder and the cost rose.

Fitting a stand alone is the best decision I made. Developing the maps for ignition and fuel took me a long, long time, but I am happy to give that work to anyone who wants it.

Wasnt sure of your HP goals, but your can get 350FWHP+ without any head gasket change, running 7 psi boost. If that HP level meets your goal it will be a little easier.
I think you will need to increase injector size though, that will require some work on your motronic or input signal massaging and some change to the timing under boost.

rgds
mike

 

That’s a very inspiring and well-done modification.
Your concern about connecting rods triggered the following:


Maybe this is as good a time as any to question yet another common Rennlist “wisdom”, this time regarding cast vs. forged rods.

Each time it comes up here the underlying evaluation is “forged = good” and “cast = not so good”, which may be true if the geometry is exactly identical and if these were the actual manufacturing processes under discussion.

I have not seen any engineering numbers comparing pull (or compression) strengths for the two rods nor fatigue strengths. If anybody has them please post.

What I have seen posted is that Porsche specifically allows mixing cast and forged (“RARST”) rods in the same engine, which suggests that they are of same strength (and mass).

Furthermore and maybe most importantly, the service manual calls the “RARST” rods “sinter/forged” and as you may know sintered steel is made (forged) from steel powder under high pressure and temperature.

In other “circles” sintered rods are considered weaker that cast rods, but in absence of hard facts, which we seem to operate a lot in, my guess based on interchangeability is that cast and sinter/forged (“RARST”) rods are of equal strength.

Laust

 

This is what I've been talking abouttttt

So 300WHP on like 5PSI? Turn it upppp