electric superchargers

[Steve Meade]

	I am looking for something between ram-air and and a full-fledged
supercharger. What about the idea of completely cancelling out any engine
pumping loss on the intake side? This would be like a 100% free-flow intake
system with the engine always getting its 1.25 liters per revolution (in my
case). At say 6900rpm (my redline) I would need about 143liters per second
or 8625 liters per minute. Or .143m^3 per second.

	Now let's suppose at 6900rpm the engine is running -1 psi manifold
pressure. That would mean I need 1 psi to reach equilibrium. 1psi is about
7000N/m^2

	.143*7000 = 1001watts

	since power = current*voltage that would be 72amps at 14volts. Now, I
believe my car has a 90amp alternator. (90 or 100 can't remember). So this
is pretty much out. (drains too much to use headlights, stereos with amp
etc.) But, I wonder what I could get for 25 amps of current at 14v. That
would yeild me about 350watts of power.

	350watts / .143m^3 = 2447N/m^2 or about .33psi. But it really isn't .33psi
yet since the blower and motor aren't that efficient. Assuming 80%
efficient motor and 80% efficient blower that .33 theoretical psi gets
reduced to .21 realized psi. Now, that would mean that the intake pumping
losses would be reduced by 5 and the volumetric loss of the engine
(volumetric loss = 1-volumetric efficiency) would be reduced by a factor of
5 as well. Now, the question is how much extra HP would I get from this? I
don't know how to calculate it. Anybody got some run-of-the-mill engine
stats and volumetric efficiency figures so I can do a hypothetical model?
But, the real question is whether or not the power gained outweighs the
loss from the alternator. If an alternator is 85% efficient than that 350
watts being consumed is really costing 412 watts at the crank. Now 1 HP =
746watts so this little puppy is only sucking up .55HP. Now if this pump
makes more than .55HP it is well worth it. I think I may have made some
mistakes in my formulas but I checked them. 

	This system also makes the best of both worlds since it not only lowers
the engine pumping power it also keeps air velocity up which should help
low-end torque a lot. 

=-=-=-=-=-=-=-=-=-=-=
Steve Meade
smeade at deltanet.com