<VV> Electric cooling fan results (long winded)

[AeroNed at aol.com]

First off, hats off to Bob, Ken and Frank for conducting this very well  
executed and instrumented test. What they did was as close to technically  perfect 
as anyone could get, an outstanding job. The presentation was also very  
good. I sat in on the presentation and kept fairly quiet, at least as quiet as I  
could. After giving this much thought during my long drive home (in a Corvair  
and still not there yet) today I have to offer some observations.
 
The test was conducted as a reproduction of what "the average Corvair  
owner", if there is such a person, would do if they purchased the fan kit. The  
stock fan was removed and the electric was installed. This is a totally  
legitimate and realistic condition for the test. However, there was no mention  of the 
condition of the heads in terms of flash or other restriction in the  cooling 
system. I would hope that any installation  instructions would  strongly 
recommend removing all obstructions to the cooling passages and insure  that the 
cylinder baffles are in place (they were on the test engine).
 
The fan kit was displayed and it was my first time seeing it. Ken mentioned  
that he could "feel air coming UP from the fan" while it was running. That was 
 because the replacement top cover was a simple flat plate. There is no other 
way  to say this besides WRONG! An axial fan moves the air directly through 
it, a  very nice column. That means that a large portion of the air going 
through the  fan is hitting that flat top cover. With no where else to go, it 
bounces right  back through the fan and that is what Ken felt. I couldn't begin to 
describe  what that does to the fan efficiency and effectiveness, not suffice 
it to say it  is not good. Ideally the replacement top cover should at least 
have sloped sides  to direct the air out to the heads where the heat is being 
generated. This would  be essential with any axial style fan, look under the 
fan shroud of any air  cooled Porsche.
 
On a somewhat side note, the Corvair fans are centripetal fans. They take  
air in at the center and "sling" it out 90 degrees from the intake, right toward 
 the heads. NONE of the Corvairs fans are very efficient in terms of airflow  
versus HP. These fans were designed to be mass produced for next to nothing. 
The  LM fan is the simplest, one piece cast magnesium. While it moves about 
the same  amount of air as the different EM designs, it is not even close to an 
efficient  aerodynamic design. Another item to note, one of the most critical 
items in the  design of a centripetal is the clearance between the edge of the 
fan and the  fixed housing. The fixed housing in the case of the Corvair fan 
is the turkey  roaster. Next time you see more than 5 Corvairs together, 
measure that  clearance, bet you get 5 different answers. And just because it uses 
14 HP  doesn't mean it needs to be using 14 HP. Once the fan reaches 
cavitation RPM,  the HP required increases dramatically while the airflow can actually  
decrease.
 
OK back to the electric fan...How come the fan can work on other cars and  
appeared to not work on the test car? That could have to do with other things  
besides the fan. Does the car where the fan works have the head deflashed? Does 
 it have a stock oil cooler or large external oil cooler? How about lower  
shrouds, are they installed? Ceramic coating or other heat treatment to the  
exhaust or other parts of the engine? All of these items can have a great effect  
on the overall cooling performance.
 
With all that said, I think an electric fan could work, even the fan as  
tested. The design of the fan and the entire cooling system would be critical in  
determining the total efficiency and effectiveness. I know that a  replacement 
fan can be designed, built and installed on a Corvair engine that  would be 
better that the stock fan. Like so many other "go fast" items, it  basically 
comes down to one question. How much would you pay for the extra  HP?
 
Ned



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