XP-360 inverted oil system

[MD8]

Hello Everyone

Our RV-8 with XP-360, fitted with inverted oil system has 5.5 hours now. We are experiencing an oil pressure drop during inverted flight. We checked the christen inverted system and it was operational. We then checked out a Pitts S-2A with Lycoming AEIO-360-A1A and the systems plumbing is fitted to the vacuum pump plate with the breather T'd into the system. Does anyone know why some Lycoming engines have the system fitted to the breather and other to the vacuum pump plate? And why this makes such a big difference? And which Lycoming is the most similar to the XP-360?

Thanks

Don and Mike

[AlexPeterson]

How much of a drop are you seeing, and is it temporary? There will be much quicker recovery to full pressure if you use the vacuum pump base pickup for the oil. The reason for that is that the oil line which goes to this pickup will remain full of oil even during normal flight. Then, the only lag is for oil to get to the top of the gear train, which takes about 1 to 2 seconds. If you are using the breather line pickup, the oil has to fill that entire line, which drains during positive flight. When I go negative, the oil pressure drops from about 75 (normal) to 40 and then back up to normal in about 3 seconds. I have the vacuum pad pickup.

[MD8]

Thanks Alex

It drops off right down and we roll upright before it reachs minimum. This take about 8-10 seconds. Would you blank off the normal breather or would you T it into the system. Our Pitts S-2B is blanked off, the oil pressure drops with a flicker of the needle then back up to about 4-6psi lower than upright flight. This is acceptable, but the RV will by the looks of it, drop below min and damage the engine.

Thanks for your reply, we're getting more confidence it will work now that someone has done the same. By the way which engine do you has and where do you fly from?

Don

[AlexPeterson]

The breather goes directly from the engine (normal breather location) to the top of the Christen reservoir. There is no tee in this line anymore.

I may have the cowl off in the next week, if so, I'll try to get a picture. Mine is an O360 in a 6A.

[frankh]

and it is set up no tee and the vacuum pad adaptor (I have an SD-8 on the back of the adaptor)

I do not see any drop at all even though I was told to expect a drop of 10 pounds or so.

Frank

[NeilMcLeod]

Mine is a Raven set up like Frank's and I do see an initial drop to about 30 then it pick backs up to the mid 50's. after a few seconds. I have about 78 to 80 lbs in upright flight.

Neil

[MD8]

Hi Guy

Thanks to all that replied.

The answer is!!! After replumbing the inverted system to the vacuum pad and testing, the same pressure drop was noted. Check this out, note the initial release date.

http://www.superiorairparts.com/Tech...ins/B07-01.PDF

I hope the newly designed sump arrives soon!

Don & Mike