A couple of days ago I noticed the oil pressure in my pp had changed. Has done about 10,000km with a constant pressure of around 95psi from about 3000rpm up. Now it gets to 95psi as usual but at about 6000rpm pressure starts to drop until it's down to 60psi at 9000rpm.
I've checked out the obvious and the oil was changed 1500km ago. Its not running a bearing and the pump is nitrided and unlikely to have worn suddenly like that. The problem is rpm sensitive not load sensitive, it doesn't matter if I accelerate hard or slow it does the same thing at the same rpm. Its like the pump is cavitating but it's never done it before & I've always used the same oil. As I say it's been fine up till now and if it was a faulty gauge I don't think it would reach 95psi at all.

Has anyone experienced this before? Any ideas?

 

The oil is either getting aerated at higher RPM, or the pickup itself is sucking air, like from the pickup to front housing gasket.

What grade/brand oil are you running?

 

I replaced the oil pickup & gasket yesterday just to be sure & while the sump was off I checked the relief valves & made sure the oil pump bolts were tight. Everything appeared to be normal. I tried another oil pressure guage also with the same result. Oil is Valvoline XLD 20-50, have used it in several engines with no problems before. BTW I have a baffle plate fitted between the sump & block.
I also think it's getting aerated but for what reason I'm not sure.

 

It gets aerated when it is sloshing around inside the rotor.

One of the big advantages of a dry sump tank is that it gives enough time for the air bubbles to float up out of the oil, plus the screens help to break up the air bubbles too. Alas, dry sump is so expensive that I must run wet sump on my PP motor, and I suffer the same falling oil pressure at sustained (several road race minutes) hi-rpms. Oil pressure returns after low rpm operation.

 

Interesting. It just seem odd that it started doing it a few days ago, not from when I built the engine.

 

Ok I put new oil in(same brand) and pressure still drops but not as far, about 10psi less than before. Now I've run out of ideas.