Vilhuer

Exact same way as 5bar measurement is taken in WSM except that cambelt is off and just oil pump is rotated. Even cranking by hand is enough to raise the pressure but he used electric drill. He tried if it makes any difference when rotation speed is increasing or decreasing etc. End result was always same much below spec value for stock setup. Oil pump should be easily able to create enough pressure for measuring. Thats not a problem unless pump or engine needs to be changed anyway.

He ended up changing new spring to another one which was sourced from somewhere else. With it it was possible to adjust desired pressure from 5bar to above 10bar just by adding different thickness washer. He set pressure to little above 8 with about 1mm thick washer. He didn't want to use stock spring as it would have required much thicker setup.

Other problem he noted with old stock spring is that it hadn't been positioned straight. This was visible from uneven wear it had in coils. So into new setup he added small rod which purpose is to keep spring straight.

I'll be doing exact same measurement when GTS engine is installed. It can't hurt to do it and adjust spring to open little above stock value. If new stock spring can't do it its easy to fit something else. Total cost will be nothing compared to possible benefits.

SwayBar

Thanks for the info Erkka.

Mike Simard

Erkka, what do you think about the idea of having oil pressure that increased proportionally to rpms? I've always heard of terms like "10psi per 1000rpms" and yes it would be desirable to have higher pressure at only higher rpms but how do you make that happen? What if the releif valve's return orifice were sized such that it acts as a restriction at high rpms thereby increasing available pressure? Any thoughts?

Vilhuer

Oil pump has probably some rpm related asjustment build into it just by its size and general design. If this is not enough I think easiest way would be to build variable relief valve and some electronics to run it. System would need inputs for pressure and rpm. Simple result would be desired valve adjustment. It shouldn't be too difficult to build such system with asjustable resistors etc and not even need to use programmable circuits, processor or other complex parts. Not sure if I would trust something like this to do so critical job though.

Making similar setup with just mechanical parts must also be possible. Setup would probably consist several differerent size valves where very small one would take care of low rpms and much larger one 6k and above. In between there would be several intermediate valves very carefully sized so that they would correspond oil pump production at each rpm range. Sizing all valves correctly would result very similar result as having same number of steps in electronic system.

Question is would such system really be needed as stock pump acts like limiter anyway. Idle oil pressure is not same as 6k rpm. Or at least is shouldn't be if all is ok in engine.

Jim bailey - 928 International

The stock pump moves 65 liters per minute at 5250 RPM according to the book , Porsche Excellence Was Expected. Or over a liter per second ! No mention of presure however. I do show the presure relief as opening at 8 Bar per the 928 service manual # 4582.21 .

123quattro

The oil pump is a positive displacement type. Flow rate goes up linearly as speed increases. As the rate tries to go up, it becomes restricted more and more by the oiling system. This in turn causes to pressure to rise. So really pressure does raise with speed. That is why there is a bypass valve built into the pump. Otherwise at high speed oil pressure would go through the roof and start blowing out seals.

Mike Simard

The oil pressure gage in a 928 seems to shoot up the the 5 bar maximum on the gage somewhat above idle. With the gage staying steady it looks like that's relief valve limited. Could that 8 bar reference be a mistake? If it were true, how does the gage and sending unit handle it, does it only report the maximum 5 bar?

Vilhuer

As factory says 4k rpm should produce at least 5bar I think 8bar limit is real. 5bar is probably enough and factory didn't see any need to display actual pressure in dash. If they had included gage that goes up to 10 or at least 8 they might have created problems for themselves as owners would notice engine isn't making as much pressure as 10k miles ago for example. By showing just 5bars max value they made sure owner is warned if something is wrong but not told what is actually going on inside engine.

Jim bailey - 928 International

The sending unit has a moving variable resistance unit inside which when maxed out sends a signal which pegs the gauge at 5 Bar ... much like a fuel tank sender, full is full also inside the sending unit an open closed switch signals for low oil pressure.

BC

Sounds like Honda!

GregBBRD

Swaybar:

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I already do this.....it's called a warranty.

SwayBar

I wasn't aware that you warranty your engines utilizing your new scraper/windage system; thanks for the info.

Mike Simard

Kevin, I'm convinced that you have no idea what you are talking about and will say anything to promote yourself and your product. You've hijacked a valid crankshaft discussion and turned it into an infomercial for yourself.

JET951

Stan , just out of curiosity A) do you know the oil temp on that day on the track during that hour . B) what was the oil viscosity and or oil brand used . Regards . BB .

SwayBar

I do not agree with your sentiment.

This whole discussion revolves around staving off a 2/6 failure. Drilling cranks, Accusumps, dry-sumping, and oil scrapers are ALL valid topics. Please tell me who is more qualified to discuss crankscrapers and windage trays?