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      08-08-2018, 07:21 PM   #1
rjahl
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Exhaust Question

I have a silly question.

From what I can see the 35is has a dual exhaust system from the turbos to tailpipes. No merges, "Y" or "X" pipes at all. So how does BMW get away with an exhaust flap on the right muffler only?
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      08-09-2018, 07:04 PM   #2
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Originally Posted by rjahl View Post
I have a silly question.

From what I can see the 35is has a dual exhaust system from the turbos to tailpipes. No merges, "Y" or "X" pipes at all. So how does BMW get away with an exhaust flap on the right muffler only?
Another note, I see the 3 series has a pipe between the left and right muffler. So closing the flap would cause equal back pressure in both sides.
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      08-10-2018, 09:19 AM   #3
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It isn't like they are totally blocking off the right side. There is a small pipe that bypasses the flap.

The conditions when this flap activates is of no real consequence to the engine.
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      08-13-2018, 06:15 PM   #4
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Quote:
Originally Posted by NoQuarter View Post
It isn't like they are totally blocking off the right side. There is a small pipe that bypasses the flap.

The conditions when this flap activates is of no real consequence to the engine.
I understand how and when the flap is closed. I'm planning to modify the maps in the tune anyways. I'm simply curious why BMW chose to close only one side. Clearly this will create some type of unbalanced loading between cylinder banks. The fuel map between bank one and bank two are even and don't have any compensation for this.

With the 3 series they installed a balance line between mufflers so they must have had a reason.
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