REFLECTOR: updraft cooling

[Dave Philipsen]

No, I think an updraft system does actually refer to the way the air 
passes the engine. And an open plenum updraft system does allow the air 
to pass the exhaust pipes.

John Dibble wrote:
> I assume that updraft simply refers to the intake air coming from 
> below as opposed to downdraft where the air comes from the NACAs 
> above.  I think the way it passes the engine is the same.  It would be 
> inefficient to pass the air past the exhaust pipes first.
>
> John
>
> Chuck Jensen wrote:
>
>>  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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-- 
Dave Philipsen
Velocity STD-FG
N83DP