Quote:
Originally Posted by Jon.
What's the function of the flapper valve?
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You know how the standard OEM exhaust has dual tips, there is a flap that covers the left hole and it acts as a silencer, makes the car more quiet at low RPMs. However, after about 3k RPM the flap is opened up so you can hear your exhaust better. The golf tee mod basically keeps the valve open all the time so you can hear your exhaust better at low RPM. since the BMW PE and Magnaflow are about sound, they don't use the flapper at all. There is a thread in the DIY section that has more info and pics on how to do it.