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When I am cruising along and acclerate a little I hear a slight flutter noise that sounds like it is coming from the back of the exhaust area. Has any heard their car do the same and have any info on this? Thanks.
If you have an A6 or A8 and are in Drive it is possible that you are hearing / feeling the switch to V8 mode and the AFM valves switching.
Try the same driving profile in MAN while using the paddle shifters. Paddle shifting keeps you in V8 mode. If you don't have the symptoms, suspect the AFM valves.
Pull up the INFO display on the DIC which shows V4 / V8 operation.
Also if you have NPP exhaust the NPP valves tend to open around 1800 rpm depending on mode selected and exhaust settings. Settings are different depending on the model year. You can also pull the NPP fuse to make the NPP valves stay open all the time.
Glad I have an M7!
Good Luck!
Ron
Last edited by RonC7; Oct 12, 2016 at 10:34 PM.
Reason: .
If you have an A6 or A8 and are in Drive it is possible that you are hearing / feeling the switch to V8 mode and the AFM valves switching.
Try the same driving profile in MAN while using the paddle shifters. Paddle shifting keeps you in V8 mode. If you don't have the symptoms, suspect the AFM valves.
Pull up the INFO display on the DIC which shows V4 / V8 operation.
Also if you have NPP exhaust the NPP valves tend to open around 1800 rpm depending on mode selected and exhaust settings. Settings are different depending on the model year. You can also pull the NPP fuse to make the NPP valves stay open all the time.
Glad I have an M7!
Good Luck!
Ron
Thanks, thats some good advice and I will give it a try and see what hapens. I drive mostly in sport mode but have the settings for the exhaust set to match which mode Im in, so does the AFM still go between 4 and 8 cyls while in sport?
Yes, the AFM is active in all modes (not sure about TRACK) with auto trans. AFM is active only in ECO with M7. Lots of information in previous threads and the manual.
Active Fuel Management (engine
cylinder shuts off)
4-Cylinder Mode
. Normal with automatic
transmission: The engine uses
8-cylinder mode when
accelerating, but changes to
4-cylinder mode when coasting.
. With manual transmission:
Active Fuel Management only
active in Eco Mode.
. Off in Manual mode with
automatic transmission unless in
Eco mode.
. Eco keeps the engine in
4-cylinder mode unless heavy
acceleration is needed.
Exhaust (variable mode exhaust
system)
Changes when the variable exhaust
valves open.
Thanks for the info guys, its much appreciated. I drove with the car in paddle mode and I could still hear the flutter but maybe not as much, or so it seemed. I also had the center screen so I could see if I was in 4 or cyl and when I heard the flutter I was still in 8 cyl. Could it still be the AFM?
Think I will pull the NPP fuse next and see how that goes. Which number is the NPP fuse?
When I am cruising along and acclerate a little I hear a slight flutter noise that sounds like it is coming from the back of the exhaust area. Has any heard their car do the same and have any info on this? Thanks.
You may have the warble noise mentioned in this thread:
If this link doesn't work, just do a search using the word warble. There is a video post in the thread that you can hear the noise. If this is what you have, you are not alone.
If this link doesn't work, just do a search using the word warble. There is a video post in the thread that you can hear the noise. If this is what you have, you are not alone.
I do beleive this may be what Im experiencing too, thank you for the link.
Flutter noise towards rear
