<VV> cooling horsepower

[Ron]

John, I think you'd be happier installing a Porsche drivetrain.  It'd be 
much easier.
RonH

----- Original Message ----- 
From: <JVHRoberts at aol.com>
To: <crawfordrose at msn.com>; <virtualvairs at corvair.org>
Sent: Wednesday, July 13, 2005 6:34 PM
Subject: Re: <VV> cooling horsepower


>
> Hence the reason for an EFFICIENT fan. The Corvair fan at high airflows 
> and
> static pressures is just beating the air up mostly.
> So, to run a calculation quickly, the specific heat of air is .241
> BTUs/pound/ºF. The density of air at STP is about 13 cubic feet per pound. 
> So...
> At 1850 CFM, that's 142 pounds per minute, or the equivalent of 34 pounds 
> of
> water per minute. Assuming there's as much HP going out the crank as the
> cooling system, a reasonable assumption, 100 HP equals 4240 BTUs per 
> minute.
> That's going to produce a temperature rise of 125 degrees F, assuming good 
> heat
> transfer. Usually on air cooled engines the heat transfer is pretty poor, 
> so,
> on a 100 degree day, the air leaving the engine, assuming the exhaust logs
> don't put any heat in there, is 225ºF. Given the poor heat transfer, 
> expect the
> heads to be at least 100ºF warmer than that! Already it's easy to see 
> things
> are  marginal.
> OK back to the other air cooled flat 6. 911 engines make WAY more power, 
> use
> less fan HP, and stay cool. There's a message in there somewhere... 
> Namely,
> get a MUCH better fan! You can't get much worse!
>
> John
>
> In a message dated 7/13/2005 8:47:07 A.M. Eastern Standard Time,
> crawfordrose at msn.com writes:
>
> You may  all recall the discussion of the cooling sufficiency of the stock
> system.  I went back to read the SAE papers and the methodology that they
> used. The data was based on the research that Chevrolet performed that it 
> takes
> 18 cubic feet of air  per minute per rated horsepower in 100 degree 
> ambient
> temps.  The airflow of the cooling system was 1850 cubic feet per  minute 
> at
> 4000 rpm.  Peak horsepower of 80 hp requires 1440 cubic  feet.  Curiously, 
> that
> is similar to the rating of the later magnesium  fan's output but as far 
> as the
> original design of the cooling system, it is  plain that 1850 cubic feet 
> is
> adequate for the original engines by more than  twenty percent.  The math 
> would
> indicate that 1850 cubic feet is  sufficient to cool to 102 horsepower.
> Therefore, the goal for 180 hp turbo  owners would have to be a implement 
> a design
> that yielded at least 3240 cubic  feet per minute to enable sustained max
> output. That is a lot of air; more  than twice the output of the magnesium 
> design
> that 180s rely upon.  I  think that the fan would drain significant 
> additional
> horsepower to drive that  much air through the cylinders at 4000  rpm.
> Crawford
>
>
>
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