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Old 02-04-2012, 03:12 PM   #40 (permalink)
aerohead
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Quote:
Originally Posted by ConnClark View Post
Yes I agree it would be a case by case basis, however I'm not sure that instantaneous mpg readings are going to tell you when you need to enable it.

Looking at the BSFC chart for my car I can see that enabling the alternator below normal road load (slowing down, braking, going down hill, etc) on the engine would be a loss in efficiency. It has to drop quite a ways to cross the threshold of using 15% more fuel where turning the alternator off would be beneficial. Everywhere else that it is above normal road load has better BSFC or is using less than 15% more fuel.

In my case it would be very difficult to determine where my efficiency dropped below normal enough to justify turning the alternator off would actually help.
Honda's logic was probably to partially deplete the battery on acceleration,then during deceleration,load the field coil and let the alternator do some 'engine-braking',bringing the battery up to full charge,rather than waste all the kinetic energy to hydraulic brake heat.
A thing like this would alter the dyno setting at EPA Mobile Sources certification testing,perhaps giving Honda a tasty MPG number to advertise.
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