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Old 11-18-2019, 10:11 AM
chrisi456 chrisi456 is offline
Join Date: Feb 2014
Location: POWAY
Posts: 26
Post Oil pressure fluctuations

I have a Titan IO370 with 230 hours on it. Due to high oil usage, 5 hours per quart that never changed from day one, I had the engine cylinders honed and re-ringed, 2 cylinders were glazed. New break in was going well, temps down but high oil usage, 1 quart per 2 hours, hopefully that will improve. When I had about 10 hours on the "new" engine, I started getting oil pressure fluctuations.

I was steady at 78 psi for most of the life of the engine, it's high do to an inverted system, then after about 10 hours, it went slowly down to 68 or so, 49 at idle for landing. I was trying to fly with a lower oil quantity, 5 quarts, to see if I would stop using so much oil, a friend with the same engine and inverted system says 5 quarts is his engine's happy place. I put two quarts of oil in thinking it might be a quantity issue, it helped initially but now changes between 70 and 77 psi. I changed the oil pressure sensor, Garmin system, and cleaned the oil pressure regulator, had no positive outcome.

I guess I'd like to know if it's safe to fly this way, why the sudden change after 230 hours and ultimately the cause. Lots of experience here, please help. Thanks
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Old 11-18-2019, 10:21 AM
j-red j-red is offline
Join Date: Dec 2015
Location: Lewes, DE
Posts: 363

What RPM are the fluctuations happening at? Are you talking steady cruise flight, or at various power settings?
Rebuilt RV-6A N94CR
RV-8 N803DR completed, flying.
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Old 11-18-2019, 10:29 AM
chrisi456 chrisi456 is offline
Join Date: Feb 2014
Location: POWAY
Posts: 26

Steady state flight, typical engine break in. Power set, not moving. I change power settings every 15 min, 65% up to 88%.
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Old 11-18-2019, 11:04 AM
lr172 lr172 is online now
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,212

If you have definitively ruled out the sensor, it's wiring, and the regulator assembly, fluctuating oil pressure levels at a constant RPM and oil temperature is concerning, possibly serious and needing a definitive source to determine the cause and therefore remediation plan in the short term.

That said, it would seem the regulator is the most likely culprit. I would consider replacing the spring and possibly the ball only because the next troubleshooting steps get tougher and more expensive. A failing oil pump would be the next likely suspect in my opinion, though there are other possible causes, including cavitation due to air ingestion via the feed circuit to the oil pump. SOme old narrow decks have a discrete feed tube, which is secured with bolt and uses a separate gasket. newer engines feed through a cavity cast into the sump and shouldn't leak unless cracked near the top.

Have you checked the sump screen? Severe blockage there could cause these symptoms and it is not uncommon to get a LOT of small carbon chunks that get stuck in the screen when you glaze cylinders.

EDIT: After re-reading your post, the reduction of symptoms with increased oil level makes the likelihood of a problem with air ingestion or inlet blockage more likely than a regulator. Yours wouldn't be the first engine to have a rag or some other item left inside of it during assembly. It is possible this potential item has moved to the center and is intermittently blocking the two slots used for the oil feed at the bottom of the sump.

I Glazed two cylinders on my first engine run and addressed them before 7 hours of run time. I had A LOT of small carbon chunks in my sump screen when I changed my oil at 10 hours. This should be the first thing you check if you haven't done so already.

N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 11-18-2019 at 11:18 AM.
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Old 11-18-2019, 04:36 PM
chrisi456 chrisi456 is offline
Join Date: Feb 2014
Location: POWAY
Posts: 26

I have an inverted oil system, therefore, no sump oil screen.
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