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DarkHorse

Petrol exhaust, muffler butterfly valve flap

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The back box has 2 tail pipes, the inner most one has a vacuum / spring opperated valve inside it that is closed at idle.

 

I found that I can test the DME electronicly generated (I think) vacuum operated flap / valve using INPA:

- Select Engine N53 MSD80 Siemens
- F6- Activate
- F1 - Stellgliedansteuerung1
- SHIFT + F2 - AbGasKlappe AGK (Exhaust Valve/Flap)
- F1 - AGK ein - Turns the Valve on for 15 Seconds
- F2 - AGK aus - Turns the Valve off for 15 Seconds
- F4 - Ansteurun Zuruck an DME - Returns control of back to the ECU (DME)

 

If not the exact same key strokes then just follow the German phrases.

 

I expect the E60 N53 525i/530i is closed at idle and probably opens the valve above 3k RPM but not able to verify. The N53 in a 330i reports to open at idle (for noise effect) then close between 1k RPM and 3k RPM.

I got bored and force my muffler valve open all the time with a cable tie. The back box sounds slightly different at idle, a bit beefy but nothing much to shout about. Going to leave it for a week or two and evaluate at various speeds and conditions. I googled around and there seems to be a wide variety of reasons for the flap (mostly hear say) but I'm not convinced by any of them being factually correct, other than for mild noise control.

 

 

Edited by DarkHorse
details and updates

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I had that in my E60, opened up second tail pipe above 4k rpms with noticeable change in bellow.

 

Didn't do that very often as by the time I had got to 4k rpms for it to activate, I was where I wanted to be and inevitably backing off the loud pedal.

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I expect the flap was much more noticable on your previous V8s :twisted:, my little i6 doesn't have the same effect sadly.

 

 

Edited by DarkHorse
typo's

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Update: Holding the muffler valve open increases the noise from the exhaust a little, as expected, just a bit more noticeable at lower revs with the window open. Going to leave the mod in place for now.

 

 

Edited by DarkHorse

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5 hours ago, DarkHorse said:

Update: Holding the muffler valve open increases the noise from the exhaust a little, as expected, just a bit more noticeable at lower revs with the window open. Going to leave the mod in place for now.

 

 

 

A similar thing can be done on the 3 series, it's just there for noise. Google the E90 golf tee mod - it's popular!

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