Can-Am Alpina Club TedFest 2015

Go Back   Can-Am Alpina Club > General Discussion > Tech Talk

Tech Talk Help and advice on technical matters for the DIYer

Site News
Latest 5 Posts Forum Author
Potential Alpina owner here 05-18-2017 06:11 PM Introduce Yourself bmb7t
B6 arrives in northern CA 04-26-2017 07:46 PM General Discussion brooke
One of our own is saying goodbye to his B7 Turbo 04-24-2017 08:34 AM Alpina Wanted/For Sale Badge
"New" B6 from Boston! 04-15-2017 05:02 AM Introduce Yourself Stirling
Set of genuine Alpina floor mats for e36 03-15-2017 11:03 AM Alpina and BMW parts RGDetroit

Reply
 
Thread Tools Display Modes
  #1  
Old 09-22-2015, 11:48 AM
MontanaRob MontanaRob is offline
Junior Member
 
Join Date: Sep 2015
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Default B7 Supercharger system unsolved issues

Hi, I'm a newer owner and have developed a particular problem that has stumped 3 good mechanics. There are so few of the supercharged models out there that it seems no one is an experienced expert in this system. I have 2 main issues that may or may not be related.

1) 07 and 08 were supercharged years (USA). My 07 is making what I would call a loud 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. If parked with hood open, you can see the intake piping jump around significantly as it chugs down the rpms. Most sc and turbo systems have a blow off or bypass valve to allow excess pressure to escape 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 pre/post supercharger compressor without a "bypass valve".

Charge air pressure regulator (pre supercharger)
http://www.realoem.com/bmw/enUS/show...17#13547966233

Pre-intake manifold temp/pressure sensor (which is just upstream of the throttle and butterfly valve assembly)
http://www.realoem.com/bmw/enUS/show...18#13627966237

See this article here where it explains that.

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

(excerpt for convenience)
--------------------------------------
"Accomplishing the basic goals – this high efficiency under part-load conditions but a high level of boost for maximum power – required far-reaching development of the engine's electronic controls and a new concept in power regulation, namely:
•A pressure regulator before the supercharger, which maintains pressure before the engine throttle at atmospheric.
•A throttle between supercharger and engine that holds pressure in the intake manifold at 50 mbar (1.5 in. Hg or 0.735 psi) less than atmospheric.

These two elements allow the engine to be controlled by Valvetronic up to the point where the intake valves have reached their maximum opening via Valvetronic; it also helps minimize any pumping losses in the supercharger, which under these conditions is essentially "coasting." At this point, the pressure regulator before the supercharger becomes the engine throttle, responding to the driver's accelerator-pedal input and regulating the supercharger's boost accordingly. Sensing and regulation functions to execute this strategy are included in the engine's electronic control system. This entire system was developed, and is patented, by ALPINA.

The supercharger itself is a new development. It's of the Radial or Nautilus type, not a brand-new concept as such but now appearing on an automotive engine for the first time. It had been patented by ZF in the 1980s, but only recently have metallurgical advances made this actual vehicle application possible. (In connection with the B7, ALPINA has several patents pending.) At full boost, the supercharger delivers a positive induction pressure of 0.8 bar."
--------------------------------

Note: I usually get a single puff of light smoke come out the right front when I come to a stop. Not out the tailpipe. (This has been confirmed as a valve cover gasket related seepage onto the exhaust). The valve stem seals are also starting to pass a little oil at 150k miles, which is a common issue but this is not a major concern yet.

2) The other main issue is that when you are BARELY on the throttle (like just touching it to maintain constant rpm), the car stutters and hesitates almost like a misfire feel). This is more frequent when you are on flat ground or downhill 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 (detailed in the link above).

Things done/observed lately:

Changed plugs (correct NGK high heat kind) - no effect
Changed ccv diaphrams - no effect
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 piping is clean and clear (except nominal oil from vapors pulled in pre-supercharger from crankcase ventilation tubing)
Mechanic found bmw vacuum code and cleared it. No other codes or errors. Was not specific enough to locate if at all current. Manual search indicates no broken hoses, pipes, etc in crankcase ventilation or otherwise.
Vacuum test via oil cap with no leaks
SC operates fine, no noises or leaks
Transmission was serviced (no effect)
Does not burn significant oil
No codes.

I feel ok driving it but the hesitation issue is a pain and it is not normal. Wondering if the backpressure can be damaging or maybe that Valvetronic system is not working the exhaust valves properly.

I am not sure if the low-throttle "jumpyness" is related to the chug problem (which reminds me of the sound and feel a jake-brake on a semi tractor )

Any help or knowledge of boards with deep expertise would great, thanks.

Last edited by MontanaRob; 09-25-2015 at 11:39 AM.
  #2  
Old 09-30-2015, 06:04 PM
bigmichy bigmichy is offline
Junior Member
 
Join Date: Jan 2012
Location: Mars, Pa and Sanford, Fl
Posts: 11
Thanks: 0
Thanked 0 Times in 0 Posts
Default Supercharger

It sounds similar to an issue I had with my 07 B7 a few years ago. If I was acceleratoring on the gas or de accelerating completely off the pedal she ran like a champ but if I tried to feather the gas and stay at a certain speed between 80 and 120 she would buck like crazy. As if fighting for. Fuel.

After three months and back and forth between BMW and Alpina getting nowhere a super mechanic snuck a camera down its throat and discovered that the secondary throttle gears were made of plastic and were worn as to not allow them to work properly. Replacing the plastic gears solver our problem.

Hope this helps
  #3  
Old 09-30-2015, 06:52 PM
MontanaRob MontanaRob is offline
Junior Member
 
Join Date: Sep 2015
Posts: 2
Thanks: 0
Thanked 0 Times in 0 Posts
Default

Quote:
Originally Posted by bigmichy View Post
It sounds similar to an issue I had with my 07 B7 a few years ago. If I was acceleratoring on the gas or de accelerating completely off the pedal she ran like a champ but if I tried to feather the gas and stay at a certain speed between 80 and 120 she would buck like crazy. As if fighting for. Fuel.

After three months and back and forth between BMW and Alpina getting nowhere a super mechanic snuck a camera down its throat and discovered that the secondary throttle gears were made of plastic and were worn as to not allow them to work properly. Replacing the plastic gears solver our problem.

Hope this helps
Wow that sounds like a great item to chase down. Thanks. To confirm, you are talking about the gears that actuate the butterfly valve in the throttle body right at the intake manifold?

Any more information on how you got or replaced the gears? Were there parts available or did you have to go to Alpina?

EDIT: I have since read up on this and it it very common for the gears to wear and create excess play in many BMW throttle bodies. There are repair gears for those that have M5s and others, but I have found none for the N62 throttle body which I share with the E65 745 as well. The good news is a new one can be had for $220, which might be a next step.

I removed my throttle body to inspect and I could move the butterfly valve just a TINY bit indicating a little play in the gears. For comparison, I looked at the butterfly valve on the boost pressure regulator (which is the first throttle body in the system) just upstream of the supercharger. This one had ZERO play in the movement. Tight.

Here is a video of the secondary throttle "play". Does anyone think this is enough to cause an issue? Thanks.

https://youtu.be/SeHFO1H8L54

Last edited by MontanaRob; 10-02-2015 at 03:30 PM.
Reply

Tags
e65 b7, supercharge

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -8. The time now is 09:24 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
vB.Sponsors