<VV> RE: fans and air flow/cooling

[Ron]

Yup, you're right on.
RonH

----- Original Message ----- 
From: "Steven R. Marti" <srmarti at netzero.net>
To: <virtualvairs at corvair.org>
Sent: Wednesday, August 03, 2005 1:19 PM
Subject: <VV> RE: fans and air flow/cooling


> Maybe describing it this way helps?
>
> The cooling air flow path through the engine and out of the exhaust ducts
> can be thought of as an orifice of a fixed area.  For the sake of
> simplicity, let's assume all the stock engine sheet metal in place and
> functioning.  Doesn't matter whether the heads have de-flashed or not as
> whatever condition you want to consider the area is a constant.   If
> pressure differential across the orifice (engine) is say 10 inches of 
> water,
> 0.5 psi, or whatever the airflow will be X.  Reduce the pressure
> differential across the fixed orifice (engine) and the airflow is reduced.
> Increase the pressure differential and the air flow is greater.  The 
> orifice
> doesn’t really care at all what generated the pressure belt driven fan,
> axial, radial, electric motor, a bunch of leaf blowers or ram air duct.
>
> Anyone disagree?
>
> Now if the spal-usa fan can produce a comparable pressure differential
> across the engine versus the stock system, then cooling air mass flow is
> comparable.  If not, but it still keeps the engine cool, we need to
> understand how and why.  Cylinder head temperature is probably a better
> comparison than oil temperature as long as everyone is using a common
> location and measurement method (unlikely).
>
> Need to see numbers before I believe it or not.
>
> Steve
>
>
> There isn't any "pressure buildup" in the Corvair engine, it's just
> that
> that is the pressure needed to get enough air flow through the fins to 
> cool
> it adequately.  Only larger and wider spaced fins would lower it.  The 
> sole
> purpose of deflashing is to reduce this flow resistance and there isn't 
> much
>
> else that can be done.  The shrouding has nothing much to do with it.
> Since a fan can only develop 10% of the pressure of the Corvair blower at
> the required mass flow rate, it's obvious that the air flow will be much
> less.  In fact, it works out to less than a third of what the engine 
> needs.
> All skeptics should buy that $600 electric fan kit and try it so the rest 
> of
>
> us can have a good laugh.
>
> RonH
>
> ----- Original Message ----- 
> From: "Bill & Chris Strickland" <lechevrier at earthlink.net>
> To: <JVHRoberts at aol.com>
> Cc: <virtualvairs at corvair.org>
> Sent: Wednesday, August 03, 2005 1:55 AM
> Subject: Re: <VV> fanz - SPAL #30102113
>
>
>> JVHRoberts at aol.com wrote:
>>>
>>> Hmmm... looks like the right flow rate, but the pressure is FAR
>>> lower than what a Corvair fan generates.
>>
>> I don't know the testing scenario that produced Spal's static pressure
>> figures - maybe it is in free air ...
>>
>> Perhaps a better question though would be, "Why is there such a pressure
>> build up in the Corvair, around 10" at higher rpms?"
>>
>> Isn't compressing air a great waster of energy? Is the 'pressure' a
>> 'requirement' to cool a Corvair? Or is it merely a sign of a poor
>> fin/shroud design? Or is it the turbulence factor impeding the flow?
>> What is the cause of this pressure build-up?
>>
>> I believe it has been mentioned here that the water pumper radiator is
>> designed to flow a high volume of air -- could the Corvair cool just as
>> well at a lower flow rate with less pressure build up? The data makes it
>> look like pressures start to build around 3000 (engine) rpm.
>>
>> Just thinking out loud -- any ideas?
>>
>> Regrettably, my query of Spal-usa about their data via email has not
>> been successful:
>>   SMTP error from remote mailer after RCPT TO:<oem at spal-usa.com>:
>>    host spal-usa.com.inbound10.mxlogic.net [216.183.119.101]:
>>    551 Mailhost is on our global blacklist
>>
>> Bill S
>> _______________________________________________
>>
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