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Old 02-01-2013, 09:42 AM
jburke4689 jburke4689 is offline
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Location: Ellicott City, MD
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Mein Auto: 2007 335i
Originally Posted by HPIA4v2 View Post
The reason for electric WP is fuel economy. Same with alternator clutch that disengage when batt condition is considered good, thus creating batt undercharge for many who don't drive long distance.

All of these unheard off until fuel cost sky-rocket and feds impose tax/penalty on car mfg when their fleet avg doesn't meet requirements.

Latest BMW feature is shutting off engine (on non hybrid) at stop, then when you switch your right foot from brake to gas, the engine starts again. Sounds like alot of work implementing this feature (especially considering safety on situation of turning left to cross oncoming traffic) but emission and fuel saving dictates at the end.
The electric water pump is for much more than fuel economy. It is for emissions by providing very fast warm up. For performance by regulating cylinder head temp based on how you are driving the car and for turbo life by cooling down the turbos after engine shutdown.

As far as the alternator clutch disengaging, it has nothing to do with battery condition. It is a completely mechanical device with no electronic elements. It absorbs shocks in the belt and tensioner system and when the rpms drop suddenly it allows the the alternator to overrun or "freewheel" as it slows down. The alternator electronics themselves and DME regulate the load the alternator puts on the engine based on battery condition and system loads.
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