S

Steve Sampson

Well Known Member
I have one of those oil pressure relief valves on the side of my engine O-320 that you turn. I need to drop the oil pressure.

Can anyone tell me roughly how many lbs change one turn should give?
 
One turn = 2psi. Mine came from ECI with adjuster screwed all the way in. I ended up backing it out all the way, approx 9 full turns. My cruise oil pressure is 87 psi., (the first tick mark after the 80 on Vans gage).

N345SF
Steve
 
Steve - thanks for that. Mine came from Aerosport Power and I will probably have to back it off 8 or 10 turns by the time I am finished. Yet on the Dyno it regulated at a sensible pressure. I cant believe it is as simple as 'If we screw this in we will screw the customer up good and proper',but it sure feels that way.

There must be a reason why we both get them poorly set, but I cant find out why.

Thanks, Steve.
 
Oil Pressure Spring

Steve:

You might also need to look at the Oil Pressure spring. There are three different springs. The 61084 oil pressure relief valve spring is the one generally installed in a low compression type of engine. You might want to verify which spring you have.

Hope this information is helpful to you.
 
Direct-reading gauge?

Steven have you tried a direct-reading gauge yet? My oil pressure reads low with Van's sending unit. I borrowed a direct-reading gauge from a mechanic friend of mine and after I'd flown and got the engine hot, I taxied in and noted the oil pressure at 1000 RPM. I quickly uncowled the engine and put on the direct-reading gauge and it showed 10 pounds more than my gauge. I just taped it on the forward top cowl.

Regards,
 
Pierre, yes I finally got a mechanical gauge on it late yesterday. It read identical to my ACS 3400 system, so from that I deduced the engine pressure is high. Hence the question below. I will talk to Aerosport Power, but the individual concerned has been away.

What I just dont understand is why I get so much higher pressure than when it ran on their Dyno. Interestingly, they got two very different readings themselves. I am pretty sure they adjusted it after the last Dyno run, but I cant think why.
 
Are you measuring the oil pressure with a hot engine or cold,the oil temperature at start up or after the oil has reached operating temperature? All of these will me a huge difference.
 
Norman, What concerns me is the oil pressure ( O-320 )is showing as 104psi at about 150/155F at 2600rpm. This is over the normal maximum.

In the factory, on the dyno the engine did 2 test runs of 30 mins at 2600 rpm where it recorded 76psi at 145f and then 85psi at 150F on 100 weight Shell oil. I am using 80 weight Total.

Yes, before you say it ALL the temps are low, but for me it is running at a higher pressure at a higher temp with thinner oil.

It makes no sense to me unless they made further adjustments after they wrote out the test sheet they presented to me with the engine. If so it seems like a pretty daft thing to do, since it only serves to confuse the customer. The point of the docs is to present a consistent history surely.

I also struggle with why the jump from 76 > 85 psi on the dyno.
 
more notes

1. My friend's Aerosport Superior O-360 engine came with the adjuster backed out all the way. He hasn't fired it up yet so I can't post his oil pressure readings.
2. The only oil pressure adjuster spring in ECI's catalog is the 61084.

N345SF
Steve
 
Another data point

My Aerosports Power O320-D2A engine runs 83-87 psi at 75% cruise. The adjustment screw is all the way out. As I remember I back it out a turn or so before it reached the stop. During take off, the pressure goes beyond 90 psi. I don't remember whether it ever went above 100 psi. At idle, it is in the 60s. I also like to see a little lower oil pressure. But, I may have to live with it.

My oil pressure spring is LW-11713. The oil pressure (rear) shown on my data sheet is in the 70s.
 
Steve

Aeroshell 100 is 50 weight oil. You mentioned you have 80 weight. Maybe your oil is too thick???

George
 
One data point... since lycoming switched to roller tappets, the shop I work at has noticed a trend of engines running high oil pressure well into the warmup cycle, then it dropping off to normal fairly dramatically.

How many of these engines are roller?

I don't know WHY this would be the case, but it has been over the 3 or so roller lycomings we've installed.
 
OK mystery solved, and thanks to all for the suggestions and concerns.

I spoke to Aerosport Power finally, and feel reassured.

The way it works is like this they tell me.

They put the engine on the Dyno and adjust the oil pressure. They stop it drain the oil and change the filter. There is lots of rubbish in the filter. They repeat the process, and again there is lots of rubbish in the filter.

The engines frequently get bits of rubbish stuck in the pressure relief valve, causing the pressure to drop, which in turn causes them to wind the valve in to achieve the pressure within spec.

Now it arrives at the customer and by now, probably at the last drain, the dirt holding the valve slightly open has escaped. So the customer has high oil pressure.

So, to adjust the pressure back to where it should be, turn the valve anticlockwise. It will drop about 3 to 4 lbs per rotation, so in my case to get from 104 down to say 85 psi will require 5 or 6 turns in total.

I feel reassured and I think the oil cooler might feel a little less stressed!

(444TX - yes you caught my mistake. I am using Total 80 which is of course a 40 weight oil.)
 
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