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View Poll Results: Do you have drone WITH the valve mod?
YES, I have a DCT and have drone WITH the valve mod. 29 36.71%
YES, I have a 6MT and have drone WITH the valve mod. 4 5.06%
NO, I have a DCT and DO NOT have drone WITH the valve mod. 16 20.25%
NO, I have a 6MT and DO NOT have drone WITH the valve mod. 30 37.97%
Voters: 79. You may not vote on this poll

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      11-29-2014, 01:20 PM   #1
Accel Junky
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Exhaust Valve Mod Comparison Video - Dueling F80 M3s

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UPDATE: POLL added regarding drone. Please vote.

One of the advantages to having multiple M3s at my disposal is the ability to make live comparisons.

Today, I had my wife assist me with comparing her unmodified stock exhaust with valves closed to my M3 with the exhaust valve mod (valves locked open). This used to be called the golf tee mod back when I had my 335i.

There is a noticeable difference but nothing crazy it seems. Hope this helps someone deciding whether to do the mod or not. The best thing is that it takes literally seconds and is easy to restore if you don't like it.



I just added this one today...cold start comparison of no mod vs exhaust mod:




Added 12/15/2014: Interior view cruising, Light acceleration, cruising with stereo:




Added 12/20/2014: Exterior view accelerating at part throttle comparing wife's unmodded F80 and my F80 with the exhaust valve mod:



How to do the mod:



This is directly from the sound engineer responsible for the F8X and may indicate why the poll shows a lot more drone reports from DCT-equipped cars:

"There are also ranges in which we have chosen to close the valves, for instance at low engine speeds in high gears. In these ranges, which are frequently selected in the automatic mode of the M DKG Drivelogic for driving at maximum efficiency, the exhaust tract in turbo engines would have a tendency to drone if there were no damping."

Last edited by Accel Junky; 02-09-2015 at 12:05 PM..
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      11-29-2014, 03:01 PM   #2
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Does it drone with valves open? It sounds like it would.
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      11-29-2014, 03:46 PM   #3
///M ARMY
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why would it drone? its on sports mode all the time.
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      11-29-2014, 03:50 PM   #4
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I don't think it drones. I think it is just like rolling around in sport plus. It is louder but not by much.
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      11-29-2014, 04:36 PM   #5
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It does drone but only at lower speeds and during street driving in 2, 3 and 4th gear. Freeway driving at cruising speed is not a problem in regards to drone.

This is different than just being in sport +, because while in sport +, the flap is constantly opening and closing part way to eliminate drone, this mod keeps the flap fully open which makes the car louder in the lower RPM range.

After a month of driving around with this mod, I just plugged it back in to stock form, mainly due to the cold starts creating earthquake like rumble and I was living in fear of being marked for death by my neighbors.
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      11-29-2014, 05:09 PM   #6
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Thanks for taking the time to put a video comparison together. You certainly are in a unique position for this sort of thing with two F80's in the garage.

So I'm gathering it would be pretty easy for an industrious owner to wire up a switch that would give you full control inside the car to command these valves to just stay open when you want, and then go back to normal ops when you want, ala Jag F type...
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      11-29-2014, 07:11 PM   #7
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Thanks for the comparison - yours is quite a bit louder than your wife's!
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      11-29-2014, 07:33 PM   #8
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Quote:
Originally Posted by ///M ARMY View Post
why would it drone? its on sports mode all the time.
According to BMW, it could drone. Even in Sport and Sport+ modes the valves close under certain conditions to minimize drone. From the exhaust deep dive interview:

Quote:
In SPORT and SPORT PLUS modes, other engine characteristics are selected for controlling the exhaust valves. At lower gears, the exhaust valves are always open, while when higher gears are selected under constant driving conditions, they are closed; however, if the load conditions change accordingly, they open up in a flash. There are also ranges in which we have chosen to close the valves, for instance at low engine speeds in high gears. In these ranges, which are frequently selected in the automatic mode of the M DKG Drivelogic for driving at maximum efficiency, the exhaust tract in turbo engines would have a tendency to drone if there were no damping.
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      11-30-2014, 01:38 PM   #9
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I just added a new video to the first post with cold start comparison.
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      11-30-2014, 01:48 PM   #10
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Hi

Sorry, but how is this fix Done ?
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      11-30-2014, 02:03 PM   #11
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Quote:
Originally Posted by wolfbane1967 View Post
Hi

Sorry, but how is this fix Done ?
Found it
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      11-30-2014, 02:16 PM   #12
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Quote:
Originally Posted by wolfbane1967 View Post
Found it
I made an instructional video yesterday. Did you find it?

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      11-30-2014, 03:01 PM   #13
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Quote:
Originally Posted by Accel Junky
Quote:
Originally Posted by wolfbane1967 View Post
Found it
I made an instructional video yesterday. Did you find it?

Thanks for the video, I'll try this When I get home
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      11-30-2014, 03:11 PM   #14
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Quote:
Originally Posted by Accel Junky View Post
I just added a new video to the first post with cold start comparison.
Awesome Values-open cold start is definitely the angry-neighbor mod ... thinking I'm gonna go for it.
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He tries to draw people into inane arguments, some weird pastime of his.
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      11-30-2014, 08:24 PM   #15
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So, is this a purely aural mod, or any other advantage to it? Forgive the ignorance if it appears as such...
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      11-30-2014, 08:47 PM   #16
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That's much better, and a bit more volume and character. I love what you've done.
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      11-30-2014, 09:10 PM   #17
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Any noticeable difference from inside the cabin?
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      12-03-2014, 10:44 PM   #18
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I love this mod!!
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      12-03-2014, 11:31 PM   #19
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Am i really debating getting out of bed walking down three flights of stairs and trying this right now haha. sounds much louder to me
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      12-03-2014, 11:55 PM   #20
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Quote:
Originally Posted by ES_TRADER View Post
Any noticeable difference from inside the cabin?
It does drone unfortunately. But the startup sound went from being embarrassing to being something you can be proud of.
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      12-04-2014, 09:48 AM   #21
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I suspect on M cars the valve is open more often than on a regular 335.
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      12-04-2014, 09:56 AM   #22
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Your car sounds so much better cold start, no comparison. Me doing this at 5:30am might not be the best thing, but boy it sounds great.
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