How does the EVAP system work
06-29-2004, 11:15 PM
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How does the EVAP system work Could one of yall help me out by explaining the entire evap system to me from a LS1? I need to adapt this to my 93 RX7/LS1 to pass CA smog, and I really dont know how I will handle that 
-Jason
-Jason
06-30-2004, 08:25 AM
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At its simplest, the evap is a charcoal-filled
cannister with an "air line" to the fuel tank.
Warm gasoline makes vapor; letting it vent
is a source of heavy hydrocarbon pollution.
Making it pass through the cannister, it gets
adsorbed to the charcoal instead (at least,
until the charcoal gets all surface-loaded).
But at least most of the tank fumes don't
escape while the car is sitting around.
Then under normal operation, the cannister
is purged with fresh air drawn through to
engine vacuum, unloading the charcoal for
next time.
Used to be a couple of check valves and a
little black can of charcoal. Now it's more of
a gizmo and has software running it, and
more ability to mess you up (like, stupid
stuff like the tank vapor pressure sensor
being bad, will keep your engine from doing
the crankshaft relearn procedure). That's
pretty damn bossy, for a can full of charcoal.
cannister with an "air line" to the fuel tank.
Warm gasoline makes vapor; letting it vent
is a source of heavy hydrocarbon pollution.
Making it pass through the cannister, it gets
adsorbed to the charcoal instead (at least,
until the charcoal gets all surface-loaded).
But at least most of the tank fumes don't
escape while the car is sitting around.
Then under normal operation, the cannister
is purged with fresh air drawn through to
engine vacuum, unloading the charcoal for
next time.
Used to be a couple of check valves and a
little black can of charcoal. Now it's more of
a gizmo and has software running it, and
more ability to mess you up (like, stupid
stuff like the tank vapor pressure sensor
being bad, will keep your engine from doing
the crankshaft relearn procedure). That's
pretty damn bossy, for a can full of charcoal.
