lumley32 wrote:as i see it, if you take 300w from an engine then you loose 300w from output! volts, amps, BHP are all derived from watts! your hp on the dyno may well go up, but you will loose else where, toque for example!
i dont see how changing the speed of bearings can make them any more efficient.
but either way the alternators i use in or race bikes are about 120mm diameter and 30mm thick, how much power dose your car use?
I think some of the discussion is now contaminated by some cross talk...
I think there is a general consensus that everyone understands that when we generate electricity through an alternator that it takes HP to do that.
I don't believe any "pulley advocates" for lack of a better term believe that we are changing the electrical draw on the alternator... that makes no sense.
But imagine you had crappy high drag bearings in one alternator, and another of same electrical properties, but with expensive made from unobtainium bearings that had almost no rolling resistance. Which would you choose for a race car. (assume they cost the same, and have the same reliability for the sake of simplicity) Obviously the lower drag version.
As a pulley advocate, what I'm saying is, if we create "all things equal" in terms of reliability, why not turn the alternator less in the range where we want more power to the wheels. Less turns has to take less energy.
Steve,
Yes, it may be a bit harder to turn, but the analogy needs one more consideration, we don't need to turn it at the same speed. Ie its really hard to ride a bike at the same speed with the wrong gear, but slow down, and its not that hard....we're changing the resulting rpm and gear ratio...not just one.
A better way to look at it would be you're pedaling furiously, hardly getting anywhere....ie wrong gear ratio, wasted energy... but you gear down, and can pedal less at the same speed even, and waste less energy.
It is almost intrinsic to the idea of this pulley discussion that we are indeed turning the alternator much faster than we need to at the rpm we race. Remember, at idle these alternators can generate enough current to run AC/radio/electric fans blah blah blah.