Quote:
Originally Posted by DaleHeinz
Stock exhaust has an actuated exhaust valve which opens and closes when cold starting and going between comfort and sport modes. It allows comfort mode to be quiet and tame while sport and sport+ become louder with pops and gurgles. Dinan exhaust is open with no valve, which makes comfort mode louder, and some guys don't like the lack of stealth for a daily.
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FYI. In my tests, the valve is closed at cold start, opens after a short time and then stays open. It does not open and close on drive mode changes.
I think it's only purpose is to create more back pressure on cold start to help the cat get up to operating temp faster.
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My 2017 M240i: MHD, xHP, Modded OE Intake, AA GESi 400 CPSI Cat DP, Dinan Mid-pipe, M Performance LSD & Rear Diffuser, BMS Exhaust Tips, Apex EC-7 Wheels, M-Tech Front Lip, iND Painted Mirror Caps, Smoked Reflectors