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7 Series - E65 / E66 (2002 - 2008)
Discussion of BMW's 4th generation E65/E66 7 Series flagship. The E65 generated much controversy, due to its radical styling and iDrive user difficulties. Nonetheless, the E65 broke records to become the best-selling 7-series iteration ever, especially after its 2005 facelift.

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  #1  
Old 08-25-2015, 11:52 AM
MontanaRob MontanaRob is offline
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Location: Atlanta
 
Join Date: Dec 2014
Posts: 8
Mein Auto: 2007 B7 , 1998 540i6
Alpina B7 Supercharger backpressure noise?

07 and 08 were sc years. My 07 is making what I would call a chug-chug-chug sound/feel as you let off the gas after you are over 3k rpm or more. It is louder at higher rpm and follows the engine speed as it slows until you cant hear/feel it under about 3k. To me it sounds like backpressure from the sc but I swear I don't recall hearing it before. Most sc and turbo systems have a blow off or bypass valve to allow excess pressure to excape when you let off the throttle, but my understanding is that Alpina's system is different and relies on the Valvetronic system and pre/post sc butterfly valves to modulate that pressure without a bypass valve? See this article here

http://myautoworld.com/BMW/cars/bmwc...07-alpina.html


Also, i usually get a single puff of light smoke come out the right front when I come to a stop. Not out the tailpipe. No visible signs of fluid spray/leak under hood or from underside on exhaust etc. The only other symptom is that when you are BARELY on the throttle (like just touching it), the car stutters and hesitates. This is more frequent when you are on flat ground on cruise control (barely on the throttle to maintain speed) It will do this in any gear at any rpm and it more noticeable at higher rpm. Other than that runs great and hard!

This is an N62 engine platform but with some different Alpina-specific internals and sc components.

Things done/observed lately:

Changed plugs (correct kind) - no effect
Changed ccv diaphrams - no effect except stopped excess oil vapors geting pulled in
Changed rubber seal plates for eccentric shaft sensors - no effect
Did the electronic reset of the adaptive transmission (step on gas for 25 sec while ignition on) - no effect
Intake is clean and clear
Mechanic found bmw vacuum code and cleared it. No other codes or erors. Was not specific enough to locate if at all current. Manual search indicates no broken hoses, pipes, etc in crankcase ventilation or otherwise.

I feel ok driving it but the hesitation issue is a pain and I'm not convinced is normal. Wondering if the backpressure can be damaging or maybe that Valvetronic system is not working the exhaust valves properly.
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  #2  
Old 08-26-2015, 08:36 AM
nervnom3 nervnom3 is offline
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Location: usa
 
Join Date: Jul 2014
Posts: 22
Mein Auto: Alpina B7
How many miles on your B7? Any oil leaks from the supercharger?
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e65 Alpina B7
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  #3  
Old 08-26-2015, 08:43 AM
MontanaRob MontanaRob is offline
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Location: Atlanta
 
Join Date: Dec 2014
Posts: 8
Mein Auto: 2007 B7 , 1998 540i6
153k. No leaks. Sc runs well.
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