REFLECTOR: Engine compartment oil cooler

[Jim Sower]

If I'm not mistaken, most canards have way excessive cowl exit area as 
it is.  This results in turbulence behind the cowl exit that "tries" to 
form an underpressure, but only results in increased cooling drag.  
There are guidelines around the ratio of exit area to inlet area that 
should be followed.  The obvious first step is to seal all the leaks, 
which should solve installation problems.  Design defects are another 
matter - my own primary oil cooler flow that exits into the high 
pressure plenum being a prime example.

Trying to "suck" air through can have adverse consequences ... Jim S.

Brian Michalk wrote:

>I have a theory about air cooling.  Of course I could be wrong.
>
>I think that having maximum vacuum in the cowling is the optimum solution.
>Plug all of the leaks in the plenum such that all of the air entering your
>intake scoops goes through the cylinders, and is "sucked" into the cowling.
>It would therefore (assuming my first sentence is correct) seem reasonable
>that any additional "leak" in the form of extra air routed through scat
>tubes to cool the oil pan, oil filter, second oil cooler, or alternator all
>results in higher pressure in the cowl, which results in less cooling of the
>cylinders.
>
>In my opinion, if you have to have secondary cooling in the cowling, provide
>appropriate exhaust for this air.
>
>How are his cylinder temps?
>
>>From my limited experience, I've seen that oil temps lag cylinder temps.
>Keep the cylinders cool, and the oil stays cool.
>
>-----Original Message-----
>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>Behalf Of Richard Riley
>Sent: Friday, April 22, 2005 3:08 PM
>To: Velocity Aircraft Owners and Builders list
>Subject: REFLECTOR: Engine compartment oil cooler
>
>I'm doing a little work on a friend's Velocity XLRG.  It's been running 
>very high oil temps.  The reason may be that the very large oil cooler in 
>the engine compartment isn't getting any pressurized air - it's just 
>sitting in front of the forward right cyl, standing in the still air of the 
>upper cowl.
>
>I'm thinking it should get pressurized outside air to one side, then 
>exhaust from the other into the engine compartment.
>
>I'm figuring on doing a plenum on the back of the cooler, and getting 
>pressurized air from the main plenum on top of the engine, or adding a 
>scoop to the bottom cowl and running a piece of SCAT to a plenum on the 
>front of the cooler.
>
>Is there a standard way for this to be done on the XLRG, or do they 
>normally have an oil cooler without any airflow?
>
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