REFLECTOR: Oil Type

[Chuck Jensen]

Tom,

Your experience fighting the oil temp probably was interesting, though one statement stood out that was particularly so; "The Lycoming gurus say that the engine wasn't set up to pump oil through 30 feet of rigid line.".

I don't know that that is a provocative statement, but it's certainly intriguing.  For instance, if the oil pump on an IO-540 is expected to put out 70 psig, the pump does not know whether there is 2' or 30' of oil line down stream of pump, or whether it is flex or rigid tubing.

If the oil is cold and viscous, some, or most of the oil may by-pass initially until it is warmed up, but that is more an issue with the pressure relief system.  The long tube run may cause by-passing for a longer period of time before warm up than a shorter run, but that is simply a few minutes at start up.  During normal operations, the pressure drop through 30' of rigid tubing is negligible, so it's difficult to see the effect.  

That being said, I don't know the gpm of the oil pump, but with 3/4" tubing, the flow rate would have to be pretty high before onset of turbulent flow in the tubing would result in rapidly increasing pressure drop.

Did the Lycosaurous gurus offer a technical explanation for their statement?  Then again, maybe I'm looking at this wrong.

Chuck



-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Tom
Sent: Monday, July 27, 2009 3:53 PM
To: reflector at tvbf.org
Subject: Re: REFLECTOR: Oil Type


How hot is your oil?? Have you gone the 2nd cooler route? Anyhow, multi 
vis is a mistake at high temps (unless it is a synthetic which you can't 
really use with leaded fuels). The base oil in multi wt is the lower 
number, as it wears the high vis (top number) decreases. If you live in 
a warm climate there is very little benefit to multi wgts as cold starts 
are their best feature. Going to 120 (60 wght) is possible but if you're 
uncomfortable with your oil temps don't give up on trying to fix.
My plane has updraft cooling, had only one cooler and very small cooling 
inlets when I first got it. I played with various things for several 
weeks to get the oil temps down. I wound up getting a 5 row stewart 
warner as a 2nd cooler and was able to place it on the top baffling. 
Initially I blasted air to it with a 3 inch duct shared off of induction 
air via a Y. While later working on hot CHTs I found that the ducting 
wasn't necessary as there was plenty of air flow through the cooler (hi 
pressure/low pressure on opposite sides of the baffling). I went from 
235+ down to 185 with this setup. The Lycoming gurus say that the engine 
wasn't set up to pump oil through 30 feet of rigid line. Probably why we 
don't get much heat out of it either when it's cold. Tom
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