There’s been some interesting discussions here of late about how the evap system handles re-fueling events in modern cars. The problem of course is the laws of physics; if you pump 10 gallons into the tank, 10 gallons of air has to come out some way or another. And it has to come out very fast to prevent the pump from shutting off prematurely.
The impression I got from the recent discussions is that with new car evap designs the air comes out 100% via the charcoal canister during re-fueling. But I noticed the other day on my 20+ year old Corolla there’s a small hole adjacent to the filler hole where I insert the nozzle. That small hole is covered air-tight by the gas cap when the gas cap is on, but is open to the atmosphere during re-filling. I’m thinking that’s where the re-fueling air comes out, rather than the charcoal canister. Or does it exit both ways? It seems like allowing that air to exit during re-fueling might contribute to air pollution. Is that vent hole under the gas cap removed in later models and the re-fueling air exits entirely through the charcoal canister?
edit: hmmm … or on my Corolla is that hole adjacent to the filler hole connected to the air exit point on the charcoal canister? So the re-fueling air in fact does exit 100% via the charcoal canister, but it just vent via that hole?