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Old 12-04-2012, 02:48 PM
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Zooks527 Zooks527 is offline
Winding up the M235xi
Location: Mansfield, MA
Join Date: Mar 2009
Posts: 5,628
Mein Auto: 2015 M235xi / 2005 Tacoma
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 ...."
2015 M235xi coupe, Black Sapphire Metallic, Black Leather, Fineline Stream trim, Steptronic, xDrive, ZPP, ZTP, ZCW, ZDA, ZDB, 5DP, hk w/ BimmerTech amp, Enh. BT
Ordered 3/12/15, Off the line 4/7/15, Delivered 5/14/15

Prior 40 years of cars: 1967 BelAir wagon / 1968 LeMans Tempest / 1970 Mustang Mach 1 / 1972 El Dorado / 1978 Corvette / 1981 Subaru GL wagon 4WD / 1983 s10 Blazer 4x4 / 1985 Bronco 4x4 / 1996 Bronco 4x4 / 2004 Passat 4motion / 2009 BMW 335i xDrive E92

Last edited by Zooks527; 12-04-2012 at 02:55 PM.
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