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      03-28-2018, 03:31 PM   #17
dpaul
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Drives: 2009 E90 335xi, 2011 E93 M3
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Quote:
Originally Posted by anorphirith View Post
if the walls weren't so porous I bet gunk wouldn't add-up so quickly
The cylinder head is not porous. What in the world do you mean?

Gunk adds up because in a direct injected engine there is no fuel in the intake to wash oil and deposits away. In the current design, the low speed blow by from the crankcase is dumped directly into the intake ports. Oil vapors hit the hot metal and carbonize. That's your gunk. It is not an inspired design. Even the German automotive geniuses don't always get everything right.
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