John Veninger

Never missed it was over 2 years old ago and this thread had gone off the deep end............

Kevin Johnson

One practical inquiry presents itself:

What drilling and oil supply paths are used in the Cayenne GTS V8? It is the closest modern Porsche engine to that which you are building. Porsche has done a tremendous amount of research into air entrainment since the 928 (read the patents).

It has recently been learned that the most official but non-official works involvement in a racing 928 engine "... was no more than fine-tuned after chosen from a set of high power output specimen in Weissach."*

This is in line with John's suggestion.

* THE MAXMORITZ SEMI WORKS 928 GTR
Porsche´s Racing Department never officially entered or prepared a racing 928 for a pure works entry. Only once Porsche decided to make it obvious to the 911 enthusiasts that they usually tended to underrate the racing genes of the 928: So Porsche "arranged" this 928GTR to compete with the then dominant 911(993GTR) on the race track. In order not to offend sensibilities of their traditional 911/993GTR customers by officially challenging them with an outright Works-928GTR, PORSCHE asked MAX-MORITZ-RACING, their long time private racing partner from next-door-Reutlingen to enter this 928GTR Cup as a semi-works car. http://www.porsche928.net/history/strosek_928cup.html So it didn´t come as a surprise, that the drivers were: Bernd Mayländer, Manuel Reuter (Porsche Works Pilots), also Harm Lagaaij (then Head of Porsche´s Design Studio). Vittorio Strosek sponsored MM with his Lightweight-Body-Parts and racing exhaust. The car was officially entered by PORSCHE-CLUB-SCHWABEN. Homologation minimum weight had to be, and actually is 1370 kg. (more infos: „PORSCHE SCENE -Germany- 12/2006 „Frisch aufgelegt: Stroseks Design Klassiker“ and 911&PORSCHE WORLD -GB- May/June 1994 „928 Cup Racer“ ) Lagaaij reports, that the car was very competitive and able to hold most 993GTR down, although the engine was no more than fine-tuned after chosen from a set of high power output specimen in Weissach. In the last race of the season at Hockenheim a crank-bearing ran dry. As the car was supposed to race in 1995 as well, she was made ready to continue her successful competition in the 1995 season. A fresh engine was installed, selected from the same lot of high output engines and tuned as before. But in 1995 Porsche´s 928-production came to an end and the car consequently was no more raced in the new season. The late Max Moritz himself then had her join his collection of historic cars. She has never been put on the road again until after his death, when the family sold the car in October 2004 -with only 24500 km on the clock. (Porsche-Weissach is the only documented owner).

Jim bailey - 928 International

OK .."The Cayenne's V8 engines are pure Porsche. These 4.5-liter V8s have all the latest high-tech systems and materials, including a unique dry-sump lubrication system that allows uninterrupted oiling at extreme angles of operation, either off road or at high lateral gs on pavement. " Looks like they fixed it

Bill Ball

I'm not sure where you are going with this. The 928 Cup cars used modifed engines: cams, forged pistons, oiling changes.

Here are some relevant and irrelevant documents about the 928 Cup cars:
http://www.norcal928.org/928cup/

Jim bailey - 928 International

Bill thanks for posting that I had not seen those for a long time. Confirms the need to restrict the oiling to the heads for high RPM use... also the advantage of adding some alloy plates to direct oil returns into the sump.

Charley B

That's what all you writers say, when you're holding out for more money.

Kevin Johnson

Pretty interesting reading. Looks like some of the more subtle points are/were being missed.

Prof. Flegl from Porsche mentions reducing the oil volume in the sump. God knows they played around with that. It ostensibly looks like this is a typo when looking at punkt 7. but I think it isn't. The oil volume is reduced in the heads by restricting oil pressure/volume. That raises the normal amount of oil present in the sump during operation. That means the oil level in the sump needs to be reduced, not left higher as some sort of imagined advantage. Little differences mean a lot in this engine. Many other engines do benefit from increased volume in the sump as a result of oil restriction to the head at high rpms. The BMW M10, for example. Not so with the 928. Punkt 8. deals with the blowby problem aggravated by a high volume of oil returning from the head. Separate problem but related. This was conclusively shown in Louie's video.

I noticed during the cross research that the Porsche 928 article on Wikipedia mentions nothing about the GKN rods. They were very proud of that and it is quite a significant event in the history of powdered metal rod use. Hint hint.

Anyway, where I was going is that the cranks were not modified by re- or alternate-drilling. This was in a wet-sumped car that would presumably have the best tweaks they knew of without installing newer technology. Compare the oiling/drilling pattern of the two bed-plate based motors (928/Cayenne GTS) and see if there are differences. I brought up the comparison because Stan is planning on running a dry sump as with the Cayenne. Comparison of the engineering is the first place to start -- that's what I do and it works.

Bill Ball

Agree there is no indication of drilling. Also, one note indicates that rods were stock. I can't read the German magazine article - it seems to be about a different racing effort.

BC

Wow - many mysteries there - different pickup points in the rear suspension, etc.

Vilhuer

Cup specs document mentions 944 head 3 bar oil pressure limit. Does this mean 944 107 139 00 pressure relief Valve? If yes, is it direct fit to 928 4 valve head? Relief valve costs close to $200 each but maybe it would be worth it to buy some extra protection for oiling system.

At least threaded pin holding it in place has same part number as pin used in 928 and 968 heads. For some reason 968 has same coil spring and ball setup as 928's. Maybe due to Variocam needing more than 3 bar to work.

DR

Yes those fit in a 928, we have been selling them for many years and have always gotten great feedback.

https://www.928gt.com/p-1774-oil-che...-pressure.aspx

Vilhuer

Thanks DR. So its one more item to must do jobs whenever 32V engine has valve covers off.

Kevin Johnson

Look at Porsche patents -- this is often a good way in general to learn about unadvertised issues. In the background of the inventions particular problems are listed as being solved.

In the case of the Variocam, I think the higher pressure is to shrink entrained air to the point where the fluid approaches ideal characteristics. They want the mechanism to operate in parallel. Entrained or trapped air in one chamber but not another will affect the order and force of actuation -- just like if you have air in one brake line circuit but none in another.

Note that the patent will try to reveal as little as possible about problems so you must read between the lines.

Here is a relevant quotation from a Porsche patent:

So, yes, Erkka, I think you are correct.

drnick

i thought the restrictor valve was to stop the lifters from recieving too much oil at high rpm?

Kevin Johnson

Volume and pressure are different but related. Higher pressure oil will bleed through clearances at a higher rate though I believe that function is asymptotic to some maximum value for a given viscosity oil.

So, up to a point, higher pressure will mean that more oil is collecting in the head waiting for drainback to the sump. This drainback is often hindered by sustained lateral G forces.

The other function of the Porsche 944 and 928 restrictor valve is to retain oil in the galley so that initial startup is working with a primed system.

The pressure relief valve at the pump and the internal design of the lifters themselves helps ward against pump-up of the hydraulic lifters at high rpm. This is a related issue.