REFLECTOR: CHT's

[Douglas Holub]

"Baffling didn't help.  I think the air will take the least path of 
resistance in spite of where you try to send it."
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That's what I found, too. I tried to direct the air where needed, but in the 
end got my hot cylinder cool by opening up the  baffles around it.

Doug Holub
----- Original Message ----- 
From: <aminetech at bluefrog.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Sunday, October 18, 2009 5:20 PM
Subject: Re: REFLECTOR: CHT's


>
>
> --- scott at tnstaafl.net wrote:
>
>
>
> The CHT's are really coming into a comfortable range.  Cruising at 165
> KTAS(low power setting) they all stay below 360, but increasing power
> to above 200 KTAS and  #2  climbed to 395, #1was about 365, the rest
> were all below 330.  I'm mostly concerned with #2 but would like to see
> #1 more inline with the other 4 as well.
>
> I'm debating installing some kind of diverter(s) inside the plenum to
> direct more air onto #1 & #2.  Anybody do that to lower CHT's with
> success?  How did you do it?  Got pictures? Controlling air movement is
> such a funny thing, sometimes what seems logical or intuitive is exactly
> the wrong thing to do!
>
> That's what I found with my Franklin.  First of all, where are your #1 and 
> 2?  Front or back?  My back cylinders (#5 & #6) ran hotter than the rest. 
> Baffling didn't help.  I think the air will take the least path of 
> resistance in spite of where you try to send it.  What worked for me was 
> putting spacers between the plenum and back cylinders to allow more air to 
> pass by.  It helped a lot.  I also made a cut out in the bottom cowl just 
> aft of the oil pan because there is a gap between the cowl and the intake 
> scoop and I felt that ingressing air was combining with the exiting engine 
> cooling air and congesting at that point.  Sometimes my CHTs read 
> identical and sometimes there's a 10-20 degree difference.  No idea why it 
> changes, but close enough I think.
>
> John
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