<VV> Electric cooling fan results

[Tony Underwood]

At 04:48 PM 7/31/2007, you wrote:
>In a message dated 7/31/2007 6:25:47 P.M. Eastern Daylight Time, 
>tonyu at roava.net writes:
> >Look at the curves, it's only slightly better. The 911 fan is WAY better.
>How much IS "way better"?  This is why I'd liked to see some serious
>comparisons in real world environments.
> >>>>Well, 911s don't overheat, and they ARE air cooled, and they DO 
> make one hell of a lot more power... Howzat?


OK... I've seen a Porsche engine with its clothes off.   The 
available cooling fin area is MUCH higher than a 'Vair engine which 
obviously makes it a LOT easier to cool.   Now:

Let's talk about those fans and NOT the design of the engine which in 
Porsche's instance was dedicated to performance and thus cooling from 
the beginning, while the Corvair engine was designed to deliver 
groceries at 40 mph.



>Hell, I still tend to consider that the cooling fan that went on Fiat
>850s looks enough like the Porsche fan to consider adapting it to the
>Corvair shroud.   Depending on year, it came in both flavors,
>aluminum and plastic.
> >>>>>Alas, a water cooled engine's cooling fan doesn't match an air 
> cooled engine's needs. Air cooled engines have less air flow, at 
> MUCH higher static pressure than a radiator.


I understand all that.   C'mon...


I'm talking about FANS.   Have you ever looked at a Fiat 850 
fan?   It ain't half bad and it's not all that dissimilar than the 
911 fan.   The Fiat also has NO external forced air through its 
radiator as well, which by the way is rather small even for a small 
displacement engine.   It *does* have a well thought out shroud 
around the fan to take advantage of everything it throws at the radiator.

The point here is to improve on what the General cooked up using 
stuff that's available today, from more modern sources.



>Speaking of which:   Why hasn't this come up?   If somebody really
>wanted to experiment, they could mount scoops on the fenders (ala
>Ferrari?  ;) ) and duct air to the inlet of the shroud via a
>fabricated plenum.   Combined with the alternator driven electric fan
>that so many people seem interested, it could be the difference
>between the electric fan system actually working and not working at
>highway speeds.
> >>>>>Well, calculate the static pressure you get from a scoop, and 
> match it to the static pressure requirements of a Corvair engine. 
> Then you'll understand why Porsche never did this trick.


They didn't have to, at least on their street air-cooled 
cars...  Their engine was easier to cool as-is by design and the fan 
cooled it well enough that they didn't *have* to add cost and 
complexity of ducting forced air to the engine.   The Porsche fan is 
also larger than a 'Vair fan so they didn't then incorporate forced air...

Not so anymore, though.   As you know, some late vintage Porsches 
have scoops in the rear fenders.   Porsche has themselves stated that 
this is a forced-air cooling duct which does enhance engine 
cooling.   I know, different designed engine etc.    But I digress...


As regards the enhancement of electric cooling with forced-air:

You missed my intent.

The electric fan as outlined by Parker/Hand/Helt came fairly close to 
being adequate for *some* driving conditions and this is with 
hardware that wasn't exactly designed to cool a Corvair engine in the 
first place.   The fact that the adapted hardware in fact did come 
fairly close in some driving conditions says something.   I didn't 
expect it to be anywhere near adequate for ANY driving conditions, 
perhaps maybe cooling an idling engine but not while actually driving 
the car.   I was surprised with their results.


However, in highway driving, it failed outright.   Now:   If you were 
more careful about picking an efficient fan and motor combo and 
supplemented the electric fan with forced-air ducted into the shroud 
(from whatever source you could pick from, be it scoops on the sides 
or where ever) would it not be possible to make this actually work at 
highway speeds?    While we're at it, we could remove the lower 
shrouds, or abbreviate them to eliminate any restrictions to air flow 
and perhaps even incorporate headers on the engine so as to duct hot 
exhaust out and away from the heads so we wouldn't have hot iron 
manifolds radiating back under the heads.   That alone will 
*Certainly* help cooling, especially with limited flow through the 
top shroud.


There's more to all this than is evident.   More can be done if 
someone were to exploit some additional tricks.   Unfortunately some 
of them may include cutting the fenders to incorporate scoops, 
something many people won't indulge.

I understand from the start that it's not practical to bolt on an 
electric fan using available affordable tech and make it work.  I'm 
not a moron.   But with additional tricks and some ingenuity, what 
P-H-H did could be improved upon especially with some help via 
forced-air supplement.   Just thought I'd ask...  and since this was 
a two-fold inquiry:


Now what about the belt driven fans?   If you used the Porsche fan in 
place of the 'Vair mag fan, in your opinion would the engine cool 
better?   (pitch notwithstanding)    Or is the 'Vair engine design 
(limited fin area) hitting diminishing returns as-is?




tony..