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Old 12-04-2012, 03:48 PM
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Zooks527 Zooks527 is offline
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Location: Mansfield, MA
Join Date: Mar 2009
Posts: 4,046
Mein Auto: 2009 335i xDrive coupe
Originally Posted by MP3_E46 View Post
Hmm.. I'd not thought of that before. So this is an air intake valve on a DI car? Presumably the carbon is sucked in from the combustion chamber and builds up over time?
Reburn from the PCV line. The crankcase vents into the intake with oil vapor in it. Most of the vapor is burned in the combustion cycle, but some carbonizes on contact with the hot metal around the valve. Another bit of anti-pollution joy.

In a Port Injection system, the fuel contacts the valve stem and helps keep it clean. In a Direct Injection system, you don't get this effect.

Extra credit: Complete this jingle: "We're the rocker arm assembly, assembly, assembly; we're the rocker arm assembly, and ...."
2009 335i xDrive coupe, Jet Black, Black Leather, Grey Poplar, Steptronic, ZPP, ZSP, ZCW, iPod/USB, HD radio, Parking Assist. Rear Fogs, Hardwire V1, ProFit G3.
ED May 12, 2009, Munich dropoff May 16, Redelivery June 22, 2009

Prior 33 years of cars: 1967 BelAir wagon / 1968 LeMans Tempest / 1970 Mustang Mach 1 / 1972 El Dorado / 1978 Corvette (kept until first Bronco) / 1981 Subaru GL wagon AWD / 1983 s10 Blazer 4x4 (big mistake) / 1985 Bronco 4x4 / 1996 Bronco 4x4 / 2004 Passat 4motion

Last edited by Zooks527; 12-04-2012 at 03:55 PM.
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