<VV> RE: fans and air flow/cooling

[Steven R. Marti]

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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