Re <VV> A/C Condensers & Fans (long)

[Bruce Schug]

On Jun 3, 2004, at 3:45 PM, Rusty Rose wrote:

*SNIP*

> Bottom line, the fans made no difference (other than
> the electrical load on the system)!  The head pressure
> test done at idle showed no difference with and
> without the fans on (2, 9" pullers on the condenser).
>
> Then we did a temperature/laod test under 3
> conditions... idle, 35 MPH with gentle stop and go,
> and at constant 65 MPH at 94 degree outside temps and
> sun load.  We gathered over 3,000 data points over 5
> locations on the car in 3 35 minute test with 2 cars.
> Even with all of that, there were no measurable
> differences because of fan use.
>
> Why?  Not sure!  I'd guess that the hole in the top
> shroud that all the air moves through is only going to
> move X amount of air, and that's it.  Adding fans will
> change the pressure in the engine compartment, but in
> our case, it didn't move "more" air overall across the
> condenser.

*SNIP*

Interesting. After receiving a good answer to my question as to why 
fans were necessary I had been thinking about this.

On a stock-type system with the condenser mounted on the firewall, I 
guess you're using fans to pull air through the condenser into the 
engine compartment. But... where is the air going? It's obviously going 
into the engine fan which is blowing it over the engine and out the 
bottom of the car. But if the puller fans are pulling in more air than 
the engine fan is, then it's going to create a pressure in the engine 
compartment. Sure, some air will blow out various leaks in the shrouds, 
etc., but there aren't many places for the pressurized air to go in a 
well-sealed Corvair engine compartment. Are the puller fans going to 
push more air through the engine shroud? Maybe. But in order to do any 
good, i.e. actually move more air through the condenser than the engine 
fan does, there has to be somewhere for the air to go. It just doesn't 
seem to me (being a tire size expert, not a battery charger or fan 
expert) that the puller fans could make much of a difference. Rusty's 
findings proves my point. Have others really seen notable improvements 
with the puller fans, even though they might not have tested and 
documented the improvements like Rusty did? After all if fit works, 
that's all that counts.

Bruce

Bruce W, Schug
CORSA South Carolina
Greenville, SC
bwschug@charter.net

CORSA member since 1981

'67 Monza. "67AC140"