what is it,
what does it do
do I need one for my 07 MCS ?
thanks

 

How much oil can a catch can catch if a catch can can catch oil? I never get tired of that. BAHAHAH

I robbed this for you to read.

Catch Can FAQ
The point of a catch can is to minimize the amount of oil vapor that's fed into an engine's air intake tract.

If you've taken the intercooler off a car with even a few thousand miles on it, you'll likely have found the inside of it to be coated with a fine layer of oil. This oil coating is also typically found in the 'Y" pipe, the throttlebody, the cold side of the turbo, and the intercooler to throttlebody hose. This oil coating is very common and isn't usually indicative of a major issue.


Why would I want a catch can?

Catch cans are useful on many, many different kinds of cars- NA and Turbo Subaru's included.

There are two, maybe three specific reasons you might want a catch can:

1) You don't want to effectively lower the octane of the gas you're running- the oil vapor that doesn't condense on the walls of your intake tract ends up in the cylinder, to be burned away for emissions purposes. The effective octane of oil is significantly lower than that of gasoline; having it in the mix will effectively lower the octane of whatever gas you're running.
2) You've got an intercooler- by definition an intercooler is part of your intake tract, and It's generally agreed that an intercooler which is internally coated with oil won't be as effective as one that's clean.
3) You want something pretty under the hood.


Where does this oil come from?

Oil gets introduced into the intake tract via two hoses- the one coming from the PCV (Postive Crankcase Ventilation) valve and the valve cover vent lines.

Who makes catch cans?

Everybody. Call your favorite vendor or hop over to their web site and see what they carry.
Can't I just vent these lines to atmosphere?

You could indeed, but there are several reasons why you shouldn't.
1) You'll lose the benefit of having the inlet's vacuum help suck filthy air out of your crank case (thanks to Wylde Horses for this one)
2) It's bad for the environment
3) It'll make a mess of your engine compartment.
4) It'd let metered air out of the system

 

It is a can with baffles in it that catches the oil mist from the Positive Crankcase Ventilation system and keeps it from burning on the backs of the intake valves and in the intake ports. This carbon build up is a known problem on direct injected engines, like we have on our turbocharged MINIs.

If you install one, it won't do any good unless you block off one of the PCV lines, the one the runs from the passenger side for the head cover to the throttle body.

For more information, do a search for Oil Catch Can or OCC, there is a lot of discussion about it on this site.

Dave