Oil pressure drop

I don’t have my engine in operation yet as my build is still a year or so away from first flight so I can’t speak from specific Rotax experience.  However, I have 50 or so years of working with and overhauling a number of engines from motorcycles to diesels and I would be more worried about the erratic oil pressure regions on the graph than the 29 psi areas which seem to have steadier readings.  It almost looks like the system is sucking air as that is generally what makes oil pressure jump around erratically.

Have you checked the crankcase pressure to ensure it is in spec?  If oil isn’t being scavenged from the crankcase quickly enough, the reservoir might get low and suck air, but it seems unlikely that would get worse with altitude.  If anything, I would think it would get better as the lower ambient pressure should increase the differential with the crankcase.

Might want to call Dean Vogel @ Lockwood as he’s got a ton of experience with these engines.

Lots of good ideas in this thread:

https://dev310.rotaxowner.com/en/912is-technical-questions/6689-oil-psi-drops-the-higher-i-climb?start=35

Shay,

The way the oil pressure so reliably tracks inversely to the altitude, this almost has to be a gauge/sender or EFIS configuration problem.  What EFIS do you have?  I believe the sender in the 915 reads absolute pressure, and that signal is later calibrated by the EFIS firmware to read as gauge pressure.  

It’s a G3X.

I take a look at the configuration. I haven’t thought about that, but given that the numbers on the ground match the expected values, I would be surprised if this is a relative/absolute configuration issue.

Shay Ohayon wrote:

It’s a G3X.

I take a look at the configuration. I haven’t thought about that, but given that the numbers on the ground match the expected values, I would be surprised if this is a relative/absolute configuration issue.

I have a G3X also with the GEA 24 and the only configuration I recall was to tell it you have a Rotax engine and set the limits you want to appear on the display. If you find there is some other configuration needed, please report back here as I will need to do the same on my installation before flight.