Dropping oil pressure in new engine......

[burgermeister]

One thing that is different these days is the Glyco main bearing shells are .0005 thinner than they were in 2013, or in 1987 for that matter. So an additional .001 clearance for all the mains if nothing else is changed - this will eat some oil pressure when hot. Did you measure shell thickness, or better yet, bearing clearance?

[fred cook]

Originally Posted by x98boardwell

Thanks Gordon,

Fred, I uploaded 2 new videos... is this what you were seeing also. Took the car for a drive and got reasonably warm... 170 degrees at engine case once back with digital temp gun.

Have a look and provide your thoughts... this seems to be pretty good which is making me think its the sending unit that which I can change in the triangle of death or something else entirely. It has great pressure once driving and the idiot light isn't coming on (that sensor is brand new also) when the oil pressure is that low at idle and engine is warm/hot.

https://youtu.be/c2e79rAQpsw

https://youtu.be/ZswYNf5SO-I

I watched your videos. I think you should temporarily install a mechanical oil pressure gauge. That should tell you "for sure" if the sender for the oil pressure gauge is bad or good. Also, it will show you how much oil pressure the engine is really making. In the past, some Porsche engines such as the 4 cylinder twin cam Carrera engines were built to make lower oil pressure to save on internal hp losses. The search begins!

[x98boardwell]

Thanks Fred.. I was curious specifically when you were test driving did the pressure go up that much which looks almost normal (like mine) or only at idle you had an issue? Any other RPM the idle my pressure is fine. Also, the light isn't coming on even when very low which I read somewhere it comes on around .5 bar.. Mine isn't even flickering.

[x98boardwell]

Burgermeister, I agree and I bet that is the actual cause as the bearings from other manufactures are typically .0002 (2 10ths of a thousandth's) off what Porsche makes so they can keep from getting sued. With that total being .0004 (4 10ths of a thousand) it allows a little more through which would lower the pressure at idle.

In addition I had the oil modification done through Armando at CCR so my #2 and #5 get full oil pressure unlike before. I don't think that would cause any additional pressure to be lost at the sending unit but it's something I've thought about during this scenario.

Appreciate the feedback!

[gsxrken]

X98 your engine looks super clean. Are you still running break in oil, or are the hot oil pressures you’re posting based on a 20/50?

[x98boardwell]

Ken, thank you! Yes, still running a 30W non-detergent motor oil.

[fred cook]

Originally Posted by x98boardwell

Thanks Fred.. I was curious specifically when you were test driving did the pressure go up that much which looks almost normal (like mine) or only at idle you had an issue? Any other RPM the idle my pressure is fine. Also, the light isn't coming on even when very low which I read somewhere it comes on around .5 bar.. Mine isn't even flickering.

When the engine was cold it acted about like yours is doing. However, once hot, the high pressure was only about 2 1/2- 3 bars at about 3000 rpms. Keep in mind that you really haven't gotten the oil/engine really hot yet. Proceed with caution!

[burgermeister]

x98, I am currently rebuilding a 3.6, and I didn't make the .0005 number up. The new Glyco main bearing shells, made in Poland, measured exactly .0005 thinner than the original shells that came out of the engine. Consequently, bearing clearances are up .001, and thus 6 out of the 7 mains would be out of spec. Still figuring out how to fix that...

I measured original shells from my 3.2 rebuild from 2011 or 2012, they are also .0005 thicker than the current Glyco shells. Didn't have a bore gage back then, but I did compare shells as a sanity check, and the new Glycos from 2012 measured the same as the shells that came out of the engine.

I have no idea how an extra .001 would affect oil pressure other than same or lower. The 3.6 had fine oil pressure before I took it apart. Rod clearances were .002-ish, mains were right around .0028 (the upper limit of the spec) with one outlier at .0036 and one at .0012. Probably not useful data at this point, but if you ever take it apart again, there is something to compare to.

If you are still using 30W, your oil pressure will be off a bit at idle when the oil gets warm.

[x98boardwell]

Burger, thank you thats great info. We shall see what happens.

I did drain the oil to inspect and put back in another round of 30 W break in oil to check the oil through a screen and check magnetic plugs... all was good. Other than light feather dust from normal break in wear there wasn't anything alarming, not that I expected there to be but still wanted to be sure or who knows, maybe a part of that seal would've come out.. worth a shot to look I guess when everything was hot.

[porschetub]

Originally Posted by Green993

One way to rule out the sender is by attaching an external pressure gauge at the sender and reading the pressure directly.

I agree 100% I never trust electric gauges until checked,not worth the gamble in the OP's case with a new build.
If the sender unit is correctly matched it could be a bad gauge unit.