REFLECTOR: Oil Pressure Effects From Cooler Arrangement

[John Dibble]

On 7/1/2013 1:29 PM, Brian Michalk wrote:
> In the spirit of sharing, I have some data related to the effects of a 
> single oil cooler vs. two coolers in parallel.  Unfortunately, my 
> logged oil temperatures are being held hostage by a bad serial port on 
> the Autronic, which logs oil temperature data.
>
> I have an oil pressure sensor mounted before the oil filter, and an 
> oil pressure sensor on the engine galley, so this measures the 
> pressure drop across the filter and oil cooler.

AND the oil line pressure drop.  I see a 12-14 psi drop between the 
cooler outlet and the engine inlet with my 1/2 oil lines.  Of course 
that assumes that each pressure sensor is reading the same, which 
probably isn't true.
>
> Last weekend, I had a parallel cooler arrangement.
> This weekend, I capped off one cooler.
>
> From searching internet sources, I should have seen a reduction in 
> engine oil galley pressure with the single cooler due to its higher 
> resistance to oil flow compared to the parallel arrangement.
>
> What I observed is a maximum of 18PSI pressure differential between 
> the two sensors.

The cooler bypass spring limits this pressure differential in which case 
some unfiltered oil is going to the engine.
>   During climbout, filter pressure reached 102PSI, and my minimum 
> galley pressure happened on roll out, and was 35PSI. The maximum 
> differential occurred during a low power cruise, about 2400 RPM, and 
> was very constant up to the point I hit redline on the temps and came 
> in for landing.
>
> I will be reconfiguring with split cooling lines, and testing for 
> series pressure differences, and will let you guys know what I find.  
> At this time, my plan is to:
> 1) fly with split lines, single cooler
> 2) fly with split lines, parallel coolers
> 3) fly with split lines, series coolers

If your 2 coolers are near each other, it might work to run a duct line 
from the NACA to the second cooler and back to the exit duct.

John
>
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