<VV> How about the cooling fans from these engines
wrokit at hotmail.com
Tue Jul 30 12:55:48 EDT 2013
> Message: 5
> Date: Mon, 29 Jul 2013 23:44:52 -0400 (EDT)
> From: BobHelt at aol.com
> Subject: Re: <VV> How about the cooling fans from these engines?
> To: jvhroberts at aol.com, mfrancis at wi.rr.com
> Cc: virtualvairs at corvair.org
> Message-ID: <7ab6f.14bdea24.3f2890b4 at aol.com>
> Content-Type: text/plain; charset="US-ASCII"
> Oh come on now!! That isn't a fan problem. That's a problem with the
> heads and cooling surfaces. A fan capable of developing greater cfm and/or
> greater pressure just isn't going to force that much more air thru the heads
> and/or rest of the engine.
> Bob Helt
Bob and others- One should always be careful when stating that you "cant" force more air through thru an air
cooled engine by increasing the pressure. Flow rise is proportional to the square root of pressure, so doubling the flow is 4 times the pressure, which seems like a tall order until you realize that there's a lot of room for improvement in the stock shrouding to reduce the pressure, and that the shroud pressure drops a bunch when the engine is hot.
For comparison, at 4000 rpm, my early turbo shroud pressure when cold is approximately 10", but
when warm the pressure is approximately 8" at 4000 rpm, and the shroud pressure apparently (I haven't done this test to verify this, just relating what others have reported) drops another 2"at 4000 rpm with the lower shrouds off, so the pressure to be raised could be as low as 6" at 4000 rpm. 4 times that pressure gives 24" and that doubles the flow to approximately 3200 cfm at 4000 rpm- 24" and 3200 cfm results in a air hp of 12.1 hp, and if the fan is only 50% efficient, this results in a drive hp of 24.2 hp, and that's a perfectly acceptable amount of power usage (8%) for a 300 hp engine- and 3200 cfm is plenty for that hp. Hard, yes, impossible, no, and yes I am working on (and have an actual prototype made) a horizontal fan that hopefully will be at least that efficient.
Time and testing will tell!
Kevin Nash 63 turbo daily driver
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