M235i Twin Exhaust query

BMW444 · 11-29-2015, 02:36 PM

I have had my Series 2 M235I now for 3 months. Bought it second-hand and it is just over a year old.

Runs and drives perfectly, I just have a few questions about the exhaust though that puzzles me.

On cold start up only 1 of the exhaust pipes operates (right hand side) then after about 30 seconds the left hand one seems to kick in - this is the one with the valve I think.

Q1 Do both pipes stay open all the time, or does the left hand pipe close again after opening after start up. I take it the right hand pipe is open all the time as it does not have a valve????

Q2 Why does my left hand pipe (the one with the valve) seem to have a little water in it most of the time only drying out completly in warmer weather where as the right exhaust only has a little water on start up and dries out really quickly, surely both exhaust pipes should react the same regardless of the valve or is the valve in the left pipe that causes the issue of water retention more in the left pipe???

Any thoughts on how the standard exhaust operates and why one pipe seems dry and the other less so???

Thanks

Cyberdemon · 11-29-2015, 06:16 PM

No, both pipes do not stay open at all times. The flap opens when asked by the system. The "Golf Tee" mod as it's referred to on the forums is a way of pegging the valve open for a more aggressive sound.

When there is condensation in the valved part of the system, there is no heat or airflow to dry it out since in normal, non aggressive driving conditions the valve will not open. That completely eliminates the exhaust flow to the left branch of the system.

The condensation should not be cause for concern. Another complaint that is common is "why is one tailpipe filthy and the other one clean".

Transfer · 11-29-2015, 11:27 PM

I have the performance exhaust and was playing around with it on cold start up today. The left pipe is not open on cold start even if you change to sport or sport+ but it does open in those modes somewhere around 60 seconds of warmup. The left pipe was nearly silent at idle compared to the right, even with valve open and visual cold exhaust clouds coming out of it. I thought this was strange.

11-29-2015, 02:36 PM	#1
BMW444 Registered 0 Rep 2 Posts Drives: M235I Join Date: Nov 2015 Location: United Kingdom iTrader: (0)	M235i Twin Exhaust query I have had my Series 2 M235I now for 3 months. Bought it second-hand and it is just over a year old. Runs and drives perfectly, I just have a few questions about the exhaust though that puzzles me. On cold start up only 1 of the exhaust pipes operates (right hand side) then after about 30 seconds the left hand one seems to kick in - this is the one with the valve I think. Q1 Do both pipes stay open all the time, or does the left hand pipe close again after opening after start up. I take it the right hand pipe is open all the time as it does not have a valve???? Q2 Why does my left hand pipe (the one with the valve) seem to have a little water in it most of the time only drying out completly in warmer weather where as the right exhaust only has a little water on start up and dries out really quickly, surely both exhaust pipes should react the same regardless of the valve or is the valve in the left pipe that causes the issue of water retention more in the left pipe??? Any thoughts on how the standard exhaust operates and why one pipe seems dry and the other less so??? Thanks
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11-29-2015, 06:16 PM	#2
Cyberdemon Brigadier General 1538 Rep 3,331 Posts Drives: 2020 X5 40i, 2018 M3 Comp Join Date: Jun 2012 Location: Long Island NY iTrader: (3)	No, both pipes do not stay open at all times. The flap opens when asked by the system. The "Golf Tee" mod as it's referred to on the forums is a way of pegging the valve open for a more aggressive sound. When there is condensation in the valved part of the system, there is no heat or airflow to dry it out since in normal, non aggressive driving conditions the valve will not open. That completely eliminates the exhaust flow to the left branch of the system. The condensation should not be cause for concern. Another complaint that is common is "why is one tailpipe filthy and the other one clean". __________________ Current: '20 X5, '18 M3 ZCP Previous: '11 E90 335i, '11 E90 M3, '16 VW GTI, '15 M235i, '13 335i, '08 TL-S, '00 Corvette
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11-29-2015, 11:27 PM	#3
Transfer Major General 5251 Rep 5,874 Posts Drives: Bronco Wildtrak, Tesla MYP Join Date: Mar 2010 Location: Issaquah, WA iTrader: (1)	I have the performance exhaust and was playing around with it on cold start up today. The left pipe is not open on cold start even if you change to sport or sport+ but it does open in those modes somewhere around 60 seconds of warmup. The left pipe was nearly silent at idle compared to the right, even with valve open and visual cold exhaust clouds coming out of it. I thought this was strange.
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