Lycoming Oil P Adjustment - Turns/psi ?

[Ironflight]

Before I just keep hunting and pecking, does anyone have a rule of thumb for adjusting the oil pressure relief valve in terms of how many psi you gain or lose per turn?

I hate standing behind a running prop....I do it, but I don't like it!

Paul

[scsmith]

I never did it with the engine running. Just a little trial by error. It was 11 years ago, so my memory of details is weak. I think a full turn gave something like 5 -7 psi change to the cruise oil pressure. I would check the log book entry for you, but it is packed in the evacuation box right now.

The one thing I DO remember is that if you don't safety wire it, it can unscrew and drop the pressure again. The first time that happened, I just thought I was dreaming. The second time, I said, "OK, it must be backing out again", safety'ed and it has never changed again.

The adjusting nut is held fixed on the regulator shaft with a hollow roll pin. I just fed the wire through the center of the roll pin.

[Ironflight]

Thanks Steve - good order of magnitude guidance.

Interestingly enough, I have never seen them safetied, despite the ease of doing so with the hollow roll pin. Even he factory doesn’t safety them! But if mine moved like yours, I’d be doing it as well.

Paul

[scsmith]

Originally Posted by Ironflight

Thanks Steve - good order of magnitude guidance.

Interestingly enough, I have never seen them safetied, despite the ease of doing so with the hollow roll pin. Even he factory doesn’t safety them! But if mine moved like yours, I’d be doing it as well.

Paul

I agree, I've never seen anyone else safety it. I wonder if they get set on the test stand and maybe a bit of loctite? Mine didn't ever move until I moved it, and then it seemed to regularly retreat to its previous set point after adjustment, until I safety'ed it.

[FORANE]

One more data point, I just asked this question to my local a&p ia yesterday. He said one full turn was about 10 psi.

[vic syracuse]

There can be different springs used in them, so the number of turns will yield different results. I have found the average to be about 3-4 psi per turn.

Vic

[lr172]

Originally Posted by vic syracuse

There can be different springs used in them, so the number of turns will yield different results. I have found the average to be about 3-4 psi per turn.

Vic

+1
Just about to write this. I vaguely remember about 4-5 different spring varieties. In my case, I was closer to 10 per turn.

Larry

[FORANE]

In the case of washers, how many psi per washer?

[vic syracuse]

Again, that can depend upon the spring, as well as using a thick or thin washer. Thick washers usually are good for 3-6 psi.

Vic

[N184DA]

Dumb question,

What direction of turn for increase/decrease PSI?