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      06-16-2009, 05:47 PM   #6
GT3 Tim
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Drives: 2014 MB E63S
Join Date: Feb 2008
Location: Sacramento, CA

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Quote:
Originally Posted by FStop7 View Post
On the M5 the charcoal filters are meant to filter gasoline fumes that vent out of the intake path when the motor is shut off. Apparently the M3 has the same tendency. It's an emissions thing.
This is exactly what it is. It is called "evaporative emissions" and all cars must meet certain criteria. Typically, California has the most stringent regulations, and cars are manufactured to meet those standards. California most definately has an evap emissions standard for new cars. CARB tests cars to ensure they meet the standards. They wil test new cars (even ones that are not released yet), and also pay people a few hundred bucks to test thier "old" cars too...to ensure they are complying with the emissions warranty as required under seperate regulation. I think the emissions warranty on cars is 7 year/100K. They can test cars anywhere within this range to make sure the manufactures are meeting the design and regulatory limits.

Most likely, because of the intake tract design, and large amount of airspace in the plenumn, gas vapors can make their way out of the intake when the car is off. Thus, they installed charcoal filter media to absorb any rogue gasoline vapors. This way, along with a number of other things, BMW can comply with the regulations.
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Tim <--- apparently likes "3" cars
2014 E63S -- The Rocket
2014 F30 328i -- Kids car
2008 E90 M3 -- Sold
2004 GT3 -- Sold
1997 M3/4 -- Sold
1995 M3 -- Sold