I now believe a catch can works but I have a question

**risky** · 11-16-2008, 10:56 PM

What oil is it catching, where is it originating from? How exactly does it work? Cleaned mine today after 4-6 weeks and there was a decent amount in it.

**slideway** · 11-16-2008, 11:02 PM

Originally Posted by risky

What oil is it catching, where is it originating from? How exactly does it work? Cleaned mine today after 4-6 weeks and there was a decent amount in it.

A Catch can stops oil mist from being drawn into your intake manifold(and then into the heads and comb. cham.) from the PCV valve, comming out by the valve cover. Over time you can get a lot of oil in the intake and can cause preignition.(knock)

**Fargo59** · 11-16-2008, 11:12 PM

yep. ive found i have low knock levels, even at the track, and when inspecting my pcv valve i usually found no oil. 1000km of using my catch can and i have a tablespoon of oil already.

**Ladybreeanna** · 11-16-2008, 11:26 PM

That what I had after 3 months & I dont drive everyday!

**fireman2118** · 11-17-2008, 12:10 AM

^^^^That's about right.

**Super T** · 11-17-2008, 10:47 AM

Better answer about where it comes from - The crankcase is full of oil just sloshing around in there while you drive. It splatters off of the moving parts and gets agitated by blow-by gases (no such thing as perfectly sealed piston rings). The blow-by in particular pressurizes the crank case - that's not good, it's not meant to hold pressure and in theory this provides an ever-so-tiny resistance to the pistons during the power stroke. So the PCV is a blow-off valve of sorts to let this pressure out. Well, all those tiny droplets of oil flying around come out w/ the air through the valve. Back in the day, when emissions and pollution were no big thing, they just vented to atmosphere. Now they go to the intake in the name of cleanliness - and the oil goes w/ that air (which is otherwise, in theory, clean).

This is the oil that the catch can catches.