Quote:
Originally Posted by rtb001
I have the 328, so just the single muffler with 2 exhaust tips. Never having cleaned them, I've noticed that one of tips has considerably more soot on it than the other. The other day, while I fired up the engine to let it warm up while cleaning snow off the windows, I noticed that at idle, pretty much all the exhaust gas is coming out the "more sooted" tip.
So is this by design, so that at idle or under low engine load, all the exhaust gas is coming out of that one tip, and during higher load, both tips are used for exhaust?
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Yup! exactly the second exhaust valve opens at around 2500 rpm, BMW did that to reduce exhaust sound when idling. If you open all your windows you can hear the second valve close when slowing to a stop.