Rob Edwards

So-

Erkka/Ake- Just for fun, if I want to try to 'degree' the GTS cams I have, how best to DIY at home? What degree wheel works on 928 cams?

Vilhuer

There are also some early S4 cams with 09 and 08 ending. AFAIK they were made from same castings as S3 cams while 00 use later different core. CS and SE should have 06 and 05 endings but they are obviously very rare.


I trust you take it with you next time you come here. We have several sets around in Veräjämäki which should be measured.

Strosek Ultra

If you check out my lift diagram (post #5) it says the marking on the end of the camshaft is 272.03 which according to the factory workshop manual is a GTS intake camshaft cylinder 5-8. Still the measured duration mismatch the factory specification. Anyone else who has checked out GTS intake cams and can verify my conclusion the factory specified duration in this case is incorrect? The cam lobe I did measure did not show any wear.

Åke

Shaun @ Tru6

Bringing this thread back as I'm a little confused on exactly what I have and hope someone can clarify what I have for cams.

Casting, placement, end cap stamp
928.105.291.6R - E1-4 - 291 09

928.105.292.3R - E5-8 - 292 04

928.105.293.5R - A1-4 - 293 09

928.105.294.4R - A5-8 - 294 08

Rob Edwards

The 291-294 castings are all S3 cams, so you have a complete set of S3 cams. Per Erkka's post in this thread, there are early S4 cams with 08 or 09 stamped on the end that were ground from the same cores as the S3 cams, so I'd guess that yours that end in -08 or -09 are later castings than the -04 one, from the period when they were doing S3 and S4 grinds on the same casting.

You could also just measure the base circle diameter of a lobe and subtract it from the maximum dimension of the lobe- The difference should be 10 mm for an S3 intake cam, 9 mm for exhaust.

Shaun @ Tru6

Thank you Rob, much appreciated. These are the cams I got from 928 Intl having ordered a set of nice cams for my 91 S4.

What is the lobe delta for S4 cams?

Are 87 cams the same as 91 cams? I know in PET they have different part numbers and thought that 87-88 was one set and 89-91 was another set.

Thanks for your help.

Rob Edwards

S4 is 9mm intake, 8 mm exhaust, vs. 10 and 9 for S3.

AFAIK all 87-91 S4 cams are the same in terms of the lobe profiles and LSA.

Here's a table of factory specs, compared to some used S4 and GTS cams that I measured myself a couple of months ago. Good agreement on the S4 cams, notsomuch on the GTS cams. I think the factory's published spec is wrong.



And here's a lift and duration curve comparison that Dennis Kao made years ago.

FredR

As you chaps are covering the differences between the various cams perhaps someone might be kind enough to comment on my setup. I have the GTS inlet mated with the S4 exhaust- a tip Louie kindly offered when he very kindly helped me setup my system. Louie reckoned it was a good combination, I think it works well, but I have on benchmark.

As a fall back I also purchased a set of S3 cams in need of modification to fit the S4 but to date have never felt the need to implement- perhaps save for a future project if I ever get round to fitting a GTS or better crank to my S4 based motor. Not much point in fitting the S3 cams if they are only marginally better than what I currently have.

Rgds

Fred

Mongo

What is the benefit of using S3 cams in an S4 car? Dyno sheets?

Clearly the longer duration of the S3 cams for the intake are better at allowing more air and fuel into the cylinders as well as the lifts. How much of a power shift are S4 cars looking at since cams have an effect on moving the power band?

When it comes to fuel and air mapping from the ECU (err LH), won't the maps need to be changed to align better with the updated cam profile?

Strosek Ultra

Pages 15-124, 15-124a and 15-140 for factory camshafts specifications.
Åke
http://www.ligeti.com/928/Porsche%20...Volume%201.pdf