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Old 05-01-2012, 03:13 AM   #17
catinthehat
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Member#: 271408
Join Date: Jan 2011
Chapter/Region: SCIC
Location: Anaheim
Vehicle:
2011 WRX
DGM

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Quote:
Originally Posted by CosmoTheCat View Post
No, you're wrong.

The charcoal canister absorbs the vaporized fuel, then in a purge cycle the vapors are sucked into the engine to be burned off.

PZEV vehicles are allowed almost zero emissions - including evaporative emissions from your fuel tank. It IS a sealed unit on newer vehicles.
Then please explain to me what the charcoal canister is for if the vapors are just recirculated, and please explain to me how the pressure build-up due to the increase in the the partial pressure of the fuel vapor is addressed.

I am by no means an expert in vehicle fuel systems, but I am an "expert" in activated carbon systems among other things.

*edit* looked up a reputable article on the subject myself. Very interesting read. A car's fuel system is by no means a sealed system, but it is certainly more complex than I thought.

Some of my own thoughts: Vapor pressure curves are different for different compounds, so it seems plausible to me that certain vapors are being adsorbed into the charcoal cannister at faster rates than others, leaving you with liquid fuel mixture that could be much different than the original formula if left to sit long enough. Sure, once the car gets running the EVAP system does its job to try and recirculate what it can, but the ratios will still be off. Interesting stuff either way.
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Last edited by catinthehat; 05-01-2012 at 03:30 AM.
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