LordKOTL
Stinger Enthusiast
To add other the other explanation posts: if my physics 101 is not rusty, it also acts as an expansion chamber.Random question what does the oil catch can do?
If you've taken a look at vacuum pumps and vacuum bleeders, on the vacuum line they usually have a can that the vacuum line is attached to. They did this so that any liquids suspended in the air being sucked into the vacuum pump fall out of suspension in the air as the gasses slow down due to less inertia than the liquid droplets and condensate. This means that, ideally, only air and gasses get pulled into the pump, while vapors and liquid/liquid droplets get collected into the can.
The catch can works the same way--with your engine being the vacuum pump, and the crankcase blow-by vapors/droplets being possible contaminates you don't want getting into the pump (engine) proper.
To my knowledge, if you have port fuel injection or throttle-body injection, any condensate or vapors coming out of suspension and onto the surfaces of your intake valves tends to get washed off by the fuel spray. Gasoline Direct Injection doesn't spray onto the valves, so gunk can build's up meaning that valves can start leaking unless you actively clean your intake and valves every so often...I think the dealer runs a can of intake cleaner through your car for the 30/60/90k tune-up. The catch can catches that gunk into the can which you should empty regularly. I try to do it every oil change (of which I've only done one so far

It was one of the 1st mods I did once I got my Stinger.