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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > 2012-2019 BMW 3 and 4-Series Forums > General F34 3-Series GT (Gran Turismo) Forum > Exhaust Vavle Mod
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      10-12-2021, 05:58 PM   #1
Call me the breeze
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Exhaust Vavle Mod

I thought I would pass along my experience with a simple exhaust mod that I recently did and had been meaning to do for awhile. As many probably already know, there is an electronically controlled valve inside one of the 2 exhaust pipes (for the 4 cylinder, slightly different for the 6er). The purpose of the valve is to meet DOT sound regulations and as it turns out has a detrimental effect on fuel efficiency. So really kind of a dumb feature. It's not new though; my 2003 E46 has a similar valve and other manufactures have their version.

There are YouTube videos that go into the process so I won't repeat here. It is actually easier to do than the videos indicate. My first recommendation is to get under the car while it is parked and cool and pull the valve controller clip out of the harness so that when it is time to do it for real you know how without breathing too much exhaust. Reconnect it before proceeding. The valve is default closed. Start by turning on the engine and putting it in Sport+. Confirm that the valve is open by feeling for hot exhaust coming out of the 2nd pipe. Pull the clip out of the harness and shut off the engine. If it is open in the off position then you have done it right. You can restart the engine and feel for hot exhaust but shut it off right away to avoid heating up the exhaust and burning yourself. The last step is to waterproof the clip and the harness in case you (or future owners) want to reverse it. I used aluminum foil, electricians tape and zip ties to tie it off neatly. YouTube videos can give the visual. All of 10 minutes to do.

This mod will give a slightly more robust and deep sound and even some mild burbles when revving. The sound inside the cabin is barely noticeable. One crazy part I didn't expect is my average fuel efficiency went up 1-2 MPG in city driving. Obviously restricting the exhaust flow by 50% has an impact. If you are looking for better sound and better fuel efficiency for free then this mod is for you.
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      10-12-2021, 06:24 PM   #2
Billfitz
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The exhaust valve doesn't affect fuel economy. If it did it would open in Eco Pro mode. It stays closed initially to allow the engine to warm up faster, which does increase fuel economy, it opens under hard acceleration to give better performance. Since it's anticipated that one intends to do some hard acceleration in Sport it's opened then in preparation for it. This isn't news to members here by any means: https://f30.bimmerpost.com/forums/sh....php?t=1220699
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      10-12-2021, 08:08 PM   #3
Call me the breeze
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1) My MPG has gone up since opening. I wasn't expecting that.
2) You admit in your post that it opens up under hard acceleration for better performance which means less restriction. Less restriction means better efficiency.
3) If you want to discourage people from sharing their experiences, you are doing a fine job with your little dig at the end.
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      10-21-2021, 04:21 PM   #4
BimmerBren
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Quote:
Originally Posted by Call me the breeze View Post
1) My MPG has gone up since opening. I wasn't expecting that.
2) You admit in your post that it opens up under hard acceleration for better performance which means less restriction. Less restriction means better efficiency.
3) If you want to discourage people from sharing their experiences, you are doing a fine job with your little dig at the end.

Your exhaust valve mod is smart. I'll look into doing it myself. I agree with you that it slightly improves efficiency because there's less restriction. That Billfitz guy never has anything nice to say although his reputation is high. He's kind of a Karen in the Bimmerpost lol. I'm glad you suggested this mod and I'm glad I'm not the only one who gets annoyed at Billfitz haha.
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      10-22-2021, 01:55 AM   #5
Markoff Chaney
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Quote:
Originally Posted by BimmerBren View Post
Your exhaust valve mod is smart. I'll look into doing it myself. I agree with you that it slightly improves efficiency because there's less restriction. That Billfitz guy never has anything nice to say although his reputation is high. He's kind of a Karen in the Bimmerpost lol. I'm glad you suggested this mod and I'm glad I'm not the only one who gets annoyed at Billfitz haha.
I also find Billfitz's input to be useless, spitefull, and generally shitty.
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