<VV> Electric fans, pusher or puller

[kevin nash]

I've been reluctant to post on alternate fan drive topics because I've seriously grown tired of it and it seems like if anybody responds to it, no matter what, all it does is keep the discussion
going- however, this one time I'm going to make an exception, and try to explain the real reason why electric fans are a bad idea. No matter if they are pusher or puller, no matter if they
can generate the required cfms at the required pressure, no matter if they are heavy or not, the real reason that electric fans are a bad idea, is that the power path, is far too indirect and
inefficient to accomplish the desired goal. Consider the power path for any electric fan that's ever been tried is belt to alternator, alternator to battery, battery to motor, motor to fan, and
fan to engine. Each step along the way has losses involved, and although the individual losses might not be so bad, the accumulative effect is sizable.
These are the efficiency's that I will assume: Belt drive 95% alternator 70%, battery 85% motor 85% and fan is 85%-  Note what the accumulative loss turns into, assuming you are
going to allow 15hp to be used at the crank: Belt to alternator: .95 x 15= 14.25hp alternator to battery: .7 x 14.25= 9.975hp, battery to motor: .85 X 9.975= 8.48 hp, motor to fan=
 8.48 hp assuming direct drive, and fan to engine = .85 X 8.48= 7.2 hp. This is only 48% of that original 15hp, and is not even close to being enough air to properly cool an air cooled
engine, in all cases.  Although the 7.2 hp may seem like a deal given that the stock fan and drive uses approximately 8 hp at 4000 rpm, I assumed that the fan was 85% efficient,
but the stock corvair fan is only approximately .28 efficient at 4000 rpm, so to compare the stock drive vs the electric, I should use the same 85% for the fan, assuming that the engineneeds 1500 cfm at 8.5" of water pressure. I used the formula hp= flowXpressure/6356X fan efficiency, and I calculate that hp required is 2.36(!) hp. I neglected the fan belt drivein this but no matter, even including that the hp use is still less than 3hp. Testing the formula on the stock fan, using 27% efficiency gives 7.42 hp, so it is reasonably close to the measured 8 hp that gm states for the late fan. I used 8.5" of water pressure because that's what I've consistently measured in my own tests (so far), assuming that the damper doorsare blocked open. I've seen 11-11.5" water pressure at 4000, but only when the damper doors are completely closed. The point of all this is that there is much, much more to be gained by a more efficient fan (or gear down the stock fan and make up the low rpm cooling loss some other way that doesn't involveusing more power) driven by a belt than there is to using an electric set-up.Kevin NashEarly Turbo, Daily driver