Originally Posted by Munit
All years of the US m3's had "brake regeneration " thing with the alternator disconnecting during acceleration. All A/C systems in bmw's and most late model cars have an A/C clutch that disengages under heavy throttle.
So with a pulley the a/c gets underdrive when cruising and at wot it does not matter as its not engaged. Then when off the pedal the altnerator you really do not want to get underdrive as that is when its charging.
Not saying there is not power to be had but it is from underdriving 2 things only-power steering and engine coolant-just not the 2 things I really want to have underdrive personally, especially living in high heat of the desert.
My point is cars awhile back gained much more from a pulley as parasitic losses were much more significant when you had the a/c engaged during WOT, alternator running at all times and heavier components.
If the m3 didn't have the water pump and went electric, it essentially would only be driving the power steering which we all know is going electric.
We are not far off from having maybe 1 or 2 things drive by a belt, or perhaps nothing at all in a few years with things going electric.
This is how the m3 should have gone about increasing performance and mileage in the f30. Take the s65, direct inject it and up the CR to boot. Upgrade to latest vanos tech and then worked on getting rid of the lat parasitic losses with an electric water pump, electric steering etc. Could have been an easy 450 hp reworked, way more efficient, and with a lighter body would have been a perfect car
Why do all of the pulleys replace the crank pulley then? We should have replacement water pump and power steering pulleys to only under drive these systems.