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Steve Sampson

Well Known Member
I am struggling through the issues of a new aircraft engine and instrumentation. Not to say it is not fun!

The attached graph is from the second (and last) flight on Monday. What concerns me is the oil pressure ( O-320 )is showing as 104psi at about 150F. This is over the normal maximum. In the factory, the engine did 2 test runs of 30 mins at 2600 rpm where it recorded 76psi at 145f and then 85psi at 130F on 100 weight Shell oil. I am using 80 weight Total.

So what I am puzzling about is this:

Do I have an engine problem? Can the oil pressure relief adjust itself? This seems unlikely to me but I dont want to bust the cooler.

or,
Do I have an instrumentation problem? Clearly i need to get a second gauge on the engine but I need to fly it to the equipment ideally.

The individual at Aerosport Power is away for a few days so I cant get help there. I cant find anything wrong with the new instrumentation. The claims there are is that it is normally accurate.

Am I right in thinking that it will be the instrumentation when the problem is finally uncovered?

PS Also, anyone know why a new engine would show such different pressures on its test, or should I assume it was ajusted between tests?
 
Oil Pressure Problem

The important thing to have is oil pressure. You do not appear to have a problem with that. Always let the engine and the oil warm up BEFORE going to take off power. Oil temperatue normally runs about 190-200 degrees farenheight. I know this takes fuel and time. Next you want to check your read out to insure accuracy. The oil relief valve uses a spring to work. The dyno run proved that it works fine so don't think about changing it. Cooler oil will always operate with a higher pressure (100 psi) but not as high as you stated. Use the new engine runs (dyno runs) as a guide for operation. Yes high oil pressure can break your cooler. Think about what changed since the dyno run. The filter, the oil, the temperature, and the time since the dyno run. Have fun!
 
leeschaumberg said:
Cooler oil will always operate with a higher pressure (100 psi) but not as high as you stated. Use the new engine runs (dyno runs) as a guide for operation.
Click to expand...

Your reply puzzles me. 1) Why does cooler oil run at a higher pressure? I thought the rear (standard) measurement was right after the pump and therefore the highest pressure in the engine. 2) You say " ....but not as high as you stated" I stated 104. Do you really mean 100 but not 104?

Steve.
 
High Oil Pressure

Having run many engines on a dyno you learn the oil pressure will be high when cold. Because of this I only run a multi grade oil like 15W50. This permits the oil to act like a 15W oil when cold and a 50W when warm. Only use a petroleum oil to break in. Synthetics should only be used after 100 hours (4 changes). This will allow the rings to seat on the nitrided cylinders then oil consumption will drop to near zero. 104 can be considered the same as 100 psi . Give me a number after the oil has reached full temperature. This may take 30 minutes of maximum cruise.
 
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Lee, we were talking at cross purposes. When you said ' Cooler oil will always operate with a higher pressure ' I thought you meant oil cooler oil.

This thread is fast becoming a nonsense because nothing relates to my original post. The point is I am running a thinner oil at a higher temperature than the dyno runs and getting higher pressure.
 
Location, location....

Steve Sampson said:
.....This thread is fast becoming a nonsense because nothing relates to my original post. The point is I am running a thinner oil at a higher temperature than the dyno runs and getting higher pressure.
Click to expand...

Hi Steve,

Have you confirmed that the same locations for pressure and temperature are being used in both tests?

gil A
 
Gil, my problem is that the person I really need to talk to, Bart at Aerosport Power, is away. Well, we all need a holiday.

The paperwork from the dyno run has a back and front oil pressure. The ones I quoted were their numbers from the back. They are the higher ones. I am using the standard point, top right behind the mount. I presume that is what they would use?

For temp I am using the standard point, just in front of the filter. I presume they would also. Even if they didnt I would have thought that unless they put it through a cooler first, which would make the info pointless, it would be pretty much the same wherever measured.

I am seriously wondering if I ought to park up until I can speak to Bart since its considerably over pressure. What can the coolers stand? I could just adjust the pressure, but this seems to be ignoring a symptom. It is quite hard to put a brand new -4 on one side when you have less than 2 hrs in it!

Thanks for your interest. Any more thoughts?
 
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