Bimmerfest - BMW Forums - View Single Post - CEL emissions issue with Akropovic Exhaust
View Single Post
Old 10-07-2012, 01:46 PM
roadkillrob roadkillrob is offline
Officially Welcomed to the 'Fest
Location: Boston
Join Date: Aug 2006
Posts: 2,647
Mein Auto: 325CIC, 335CIC
Originally Posted by gotrice415 View Post
Ok so you just said it youself. How is that not accurate? There are dpdw's that control the wastegate which is vacuum to it. Since you have an exhaust installed by VDC im sure they blocked off the vacuum line and retrofitted the DME software to ignore or not activate the flap since it ha been deleted.

So if you dont do that what do you think the DME does? Sets a fault for activation and vacuum leak causes lean mixture faults.
Do you have any idea what you are talking about???????????????

The flap on the tailpipe is for noise regulations only, blocking of the vacuum line has no effect on anything at all (won't even throw a code and certainly has nothing on earth to do with emissions).

Wastegates are on the turbos, not the exhaust flapper at the end of the tailpipe. Wastegates are vacuum controlled also (only thing you have correct) to control the volume of exhaust gas driving the turbines.

The DME measures the difference in pollution on the primary cats, there is a sensor before and after, 2 cats on the N54's, 1 on the N55's. Secondary cats are not monitored by the DME.

Now back to the actual question - Op lists that he has an M3, so no turbo's. My guess that something was damaged when the exhaust was installed, either wiring to the O2 sensors or an O2 sensor itself if they needed to be removed to install the exhaust - the car is seeing too much of a difference across the primary cats. M3 also has dual primaries with an O2 before and after, there should be no issue with the install going anywhere near those, so either the had to much with something up front or it is just a coincidence.

2008 335i Vert Montego/Saddle/Grey Poplar
2013 Mercedes C63 AMG Obsidian Black/Black
2016 X5 M-Sport Mineral White/Mocha Design Package/Fineline Oak

Last edited by roadkillrob; 10-07-2012 at 01:48 PM.
Reply With Quote