OK,  here's an oil pressure question.

I've been running my new (fast build) TSIO550E engine for some 45 hours now.  I recently was flying with an instructor who noticed the OP fluctuating for no apparent reason, all other parameters static and in level cruise.  Being the new kid, I had seen this but assumed the fluctuations were not out of bounds.  It had caught my attention, but TCM was not too concerned, and so I've been looking at it without knowing what to do.

The graph below depicts the oil pressure (black saw tooth line) during level cruise condition.

The oil and filter has been changed (a bit earlier than the planned 50 hrs), oil sent for analysis (pending).

The oil pressure transducer did not have a grounding wire to the sensor, so I rigged one, but this had no effect during a recent long flight.

Paradoxically, if you pull the throttle, reducing MAP, the fluctuations and the overall OP increase briefly (but notably).

Of course, if you close the oil door and raise oil temp, the overall oil pressure lowers, but continues to bounce around.

Some have suggested the next step would be opening and cleaning the oil pressure relief valve.  One idea was to vent any trapped air in the hose exiting the oil pump fitting and going up to the sensor (mounted on the fire wall), thinking the air was causing some compressive fluctuations.

Others have mentioned the oil cooler vernatherm.

It does not seem to be related to radio COMMs, as I have deliberately turned off all radios (during this 17 min plot) and observed no difference.

TCM's first and only thought is a sensor (electical) problem.  They have asked me to check for same fluctuations on the ground, static at 1700 RPM.  If observed, then hook a mechanical guage and watch.  If not seen on the steam guage, ignore it or change sensor.  If not observed on the ground, then they had no further contributions (yes, I have his name, date and time of the warrentee call).

Any incredible insights?  Shared for my own benefit and perhaps to help others.

Jeff Liegner

N334P in New Jersey

 

This is a 17 min plot of RPM (scaled down by 1/30th), oil temperature (scaled to 1/3rd), plus MAP, Fuel Flow and Oil Pressure (seen as the black saw-tooth plot).  Flight was level at 15,500'

RPM (red) is constant except for a brief RPM increase to 2600 to see if this had an effect.  Oil temp (brown) fairly constant.  Fuel flow (blue) from ROP to LOP.  MAP (yellow) initially at 36" then lowered to 32", again held constant.

You'll notice the oil pressure fluctuates from low 60's to as high as (briefly) 92 psi while engine parameters remain static, while also fluctuating within each moment as much as 14 psi.

PS  This was data pulled of the Chelton in a complicated dance of data crunching, in case you wanted to know.