REFLECTOR: updraft cooling

[Chuck Jensen]

I've not seen the layout of an updraft cooling system, but does the air
get preheated from passing by the exhaust pipes before it every gets to
the cylinder heads?  If it does, that would greatly increase the volume
of air required because of the reduced delta T across the heads.  By
comparison the top NACAs provide clean, cool air directly to the CHs.
Too simple--I must be missing something?
 
Chuck Jensen 
  
-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of John Dibble
Sent: Saturday, February 17, 2007 2:41 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: updraft cooling


I think the amount of air going past the cylinders will determine the
degree of cooling, so it's a matter of making the NACA or armpit scoop
and ducts big enough for sufficient air. 

John 

Ron Brown wrote: 

	And, the downdraft NACA cooling for some unexplainable reason,
runs about 40 degrees cooler than the updraft cooling.  Mark Machado
converted what is now the factory trainer from updraft to downdraft and
says the heads ran 30-40 degrees cooler.  My 173 Elite RG runs 360-370
max on a long climb out and 320-340 degrees during a 2600 rpm/155 kt
cruise.  I highly recommend the NACA cooling system.

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