Anyone knows the reason why?

[///Morgan]

Hi;
I was wondering if somebody can explain me the real reason of the exhaust bypass valve?. Is it only for quieting the exhaust sound?
I have just unpluged the actuator in the trunk on my 335i but I am worried about some possible drawbacks on that. Did also the golf tee mod on my R32 for a few miles.
Some bad experiences??
I didn´t try the golf tee mod on the BMW... which one will be better?

Thanks in advance!

[coco_m3]

golf tee?

[rocketpop]

golf tee?


There is an actuator connect to a flap that open and closes inside the exhaust pipe. One of the earlier ways to keep the flap open was to put a golf tee in the connecting vacuum hose. Other way is to put a BB in there, or even unplut the actuator plug.

It just makes the exhaust louder, not sure if there is any downside to it.

http://www.1addicts.com/forums/showt...light=golf+tee

[EvanB85]

I believe the main reason is for EU noise regulations. With both pipes open it is no boubt louder. Also, I think it might help to warm up the cats a little quicker... that is purely conjecture though.

[///M ichael]

Flapper mod!

[knightps]

I have seen people simply pinch the vacuum hose with a binder clip to keep the valve open. Is there any serious down side to this approach?

[jeremyc74]

My guess is this was just done to meet noise regulations for normal driving, and still have a free flowing exhaust under WOT. It would be hard to imagine any negatives coming from this other than the increased sound level.

If there were issues with cat temps it would certainly show up on aftermarket exhaust systems that are more open, and there are a lot of 335s running around with aftermarket exhaust on them.

[F0Bman]

From my experience its to reduce, noise, but when done smartly can actually increase back pressure for NA applications.