Quote:
Originally Posted by gtengr
It's different from the AC compressor because the rotor in an alternator is a spinning electromagnet, so resistance can be altered by changing the current flowing through it.
Found a relevant passage in the 2017 Updates pdf, pg. 89 of 120:
Battery Condition Sensor
The previous current sensor always maintained control to keep the battery fully charged. The battery condition sensor calculates the charge status, level of deterioration and internal resistance of the battery from data such as its voltage, current and temperature, and controls charging so that there is always spare capacity available. This allows the recharging rate to be increased when decelerating, which improves fuel efficiency.
If fuel efficiency is being improved, then resistance of the alternator under load is being reduced. I'm not sure how much, but I think it's safe to say the already small number being thrown about for power consumed by the alternator can be chopped in half or more for the +2017's. I think the E92 M3's alternator disengages completely and that was 2007.
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Interesting.
I think it was 4hp is what someone calculated for when in use. Making the alt 3.4hp to spin with pulley. I wonder how much of that resistance goes away when not charging. If it’s half then still leaching 2hp / 1.7hp with pulley. Either way it was semi cheap after already getting water pulley and belt. Kind of a why not mod at that point. And besides going FI im pulling at straws to get any small gains at this point.