333pg333

You deem what I said as being "So critical" yet you seem to be lacking a mirror, filter and common courtesy. Odd processing. You display traits of Bipolar disorder. Have you not been diagnosed or just off your Meds?

Makis

On my S2 when I bought it about 10years ago it had 2 valve springs broken like this. It took me 6 months to work out what was wrong as the car was running but felt low on power. I only found out eventually when an exhaust valve blown out and lost compression on one cylinder. Had to remove the head. I did replace all springs then. It does look that those valve springs are prone to failure on S2 wonder what is causing it.

johntorg

I raced my S2 all last year with no broken springs. This was my spare engine. I guess over-revving may be a factor.

Fishey

The normal 944's have batch fire 1and3 and 2and4. I think the S2 might be sequential fuel injection but it would be easy enough to find out with a wiring diagram. I would also test the wiring harness/ecu output to that cylinder with a scope, I would also move the injectors around to see if that injector is a problem.

This has some information you might find helpful.

http://www.9ss1.dk/porsche944/garage/vol1a/vol1a.html

johntorg

Thanks, the problem has been solved. It was a broken exhaust valve spring. The 91 S2 uses a single driver and batch fires all of the injectors at once. It also uses unique, expensive and difficult to obtain, high impedance injectors, I did find a substitute injector from a 90-92 VW Corrado G60, and have a set off at Witch Doctor for cleaning

mblaszak

I've found it common that the outer valve spring will break. We do 1-2 repairs a year like that. I have the tools to pull that broken spring out with me all the time, even at the track, and carry spare valve springs with me in the trailer.
What I have found however is that in my experience it was ALWAYS the #4 cylinder that fails, and it is always an intake valve.... have done this job 17 times now.... it was always a pattern that bothered me. Typical symptom is that the car however runs perfect up to 2500-2700 RPM. However higher than that the inner spring can no longer close the valve on it's own and the engine starts to flutter badly. Drop the revs and that fixes itself again.
Curious that your car with only the outer spring broken would not idle properly on the inner valve spring.

FYI, ALL 944/S2/969 models batch fire all 4 fuel injectors at the same time. None of them are sequential or semi-sequential as they fire from ONE common buss in the ECU. It does split out in wiring to two pairs of wires, but when fired off of one buss, all 4 injectors fire at the same time.

johntorg

Thanks for the info. i was pretty sure that was the case on batch firing, but only looked up my specific car. In my case it was an exhaust valve. It would start on 4 cylinders, but switch to 3 after a few seconds. After replacing the spring, it seems to run fine. I'm off to Sebring the weekend for 3 days of racing, and I guess I should bring along my "McGiver" valve spring compressor and an extra spring. BTW, I am using your control arms on the car and have a question. The monoballs that screw into the arms don't have any jam nuts on them. I realize that they can't unscrew, but is that normal?

mblaszak

Yup, ditched them years ago as they really served no purpose. They are now secured with Red Loctite to prevent moving easily when the arms are removed, but no longer have the jamb nuts installed as a way of dropping just a few more ounces. Also for those who needed more adjustment due to a badly twisted chassis, the jamb nut caused them to run out of thread adjustment prematurely when setting for tracking, so to make things easier for everyone, I just left them out of later arm sets.

Thanks for asking. Sorry, don't want to hijack your thread. Glad your car is running well again!

Makis

For the stats here, my 2 valve springs that broke were on cylinder #3 with one inlet and one exhaust valve. The exhaust valve eventually burned I presume due to valve float as the inner spring that was still OK was not strong enough to close the valve so it can cool down by picking up coolness from the cooler cylinder head. The inlet valve was OK as it was getting cooled down by the fuel/air intake mixture.

333pg333

Wow...Markus Blaszak on Rennlist. Now that's something you don't see everyday!

Eric_Oz_S2

My thoughts exactly.

mblaszak

LOL... I've been on Rennlist now since before it was Rennlist, probably close to 20 years now, but yes, you don't see me on here often. Back in the day (chuckles) it was an email based list not a forum base, and yes I was much more active then. The problem with the forum base is I just don't have time to got through everything in the same way.

Cheers

Markus

333pg333

It's a shame more people like you just don't have the time Markus. This board suffers with the lack of real long term experts. Especially those versed in transaxles and racing. I bought a few bits and pieces from you some years ago from way down here in Sydney, Australia. I think the modded clutch fork is still on my racecar build.

Having said that, there would be a few builds and projects on here now that I'm sure you'd be quite blown away by. Here's a few I can think of just for now. Some of these have sacrificed the i4 for a V8 but you have to admire the overall build specs.

https://rennlist.com/forums/924-931-...for-400hp.html

https://rennlist.com/forums/944-turb...r-project.html

https://rennlist.com/forums/944-turb...ld-thread.html

https://rennlist.com/forums/944-turb...ld-thread.html

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

https://rennlist.com/forums/944-turb...ing-mount.html