Catch Can
Positive Crankcase Ventilation and oil issue.
A common practice on many modern engines is the plumbing of PCV (positive crankcase ventilation) lines back into the intake - this is done in accordance with emmissions regulations.
The issue with this is that many engines have this excess air bled from the rocker covers where there is lots of oil flying around, so this excess air becomes heavily contaminated with oil before entering the intake……as you may know oil retards the ignition process and therefore dampens power.
The common method to reduce this oil re-entering the intake is to tap into the PCV line and install a catch can - catch cans are basically a filter allowing air to pass through while catching as much oil as possible. The quality of cans varies greatly - some cans are nothing more than that, a glorified can with an inlet and outlet while others (such as the one i have on my car) are more elaborate with internal baffles and filtration to catch as much oil as possible.
After i designed my can and had a welder mate fabricate it i felt i would start marketing them but due to the cost and complexity of making the stainless can and the fact there are so many cheaper and mass produced (and often inferior) cans on the market we decided to not pursue this avenue.
My can has an outlet on the bottom which has some clear tube attached which is terminated with a bleed valve. This allows monitoring of the amount of oil caught and a convenient way to drain off the oil. I do know of some designs which run the outlet straight into the dip stick tube which is no maintenance but i dont like the idea of putting the oil back into the system without knowing how much i am catching. The oil can often be contaminated with moisture and turns a horrible grey colour so i prefer to bleed it off and safely dispose of it.
Tags: catch can, Commodore, Holden, positive crankcase ventilation