Quote:
Originally Posted by lucid
This is a stretch, but as an intellectual exercise: the main alternator is a "load" in the system, and opposes crankshaft motion slightly. So, if you're in gear while decelerating, the alternator opposes the motion of the car, and would have some kind of small effect on slowing the car down. If one could find a way of increasing the load the alternator produces only while braking, the effect would be amplified. But regular alternators are not designed to that, and their belt connection to the shaft is fragile. If that connection was stronger, and if the alternator load could be increased at will, it would be more like the regenerative system in the hybrids, but the engine would definetely not feel smooth when breaking, so probably a bad idea...Also, what would you do with all that extra current generated by the alternator, which would require a bank of batteries to store...
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To add to this, the additional load on the crankshaft would be proportional to the current flowing in the alternator, so it would be possible to manage this load electronically to give smooth braking (though I don't know how BMW has actually implemented it).
A properly implemented system would to some extent improve fuel economy and power as well as conserving brake pads. Someone would need to do the calculation to determine whether these effects would be measurable or it is just marketing guff
