What is a catch can, and what do they do?
By nature some oil, fuel and even water escapes from the motor during normal operation and ends up in the crankcase. In standard form, this film of oil is sucked back through the positive crankcase ventilation line (PCV) and ends up in your air intake, where it goes back into the motor to be burnt in the combustion process.
A catch can sits in between your crankcase and the PCV, and it is designed to separate the fluid and mist from the air that makes its way through and catch it in the bottom of the unit.
Oil catch cans are simple devices that can greatly benefit direct-injected engines. They prevent oil and other contaminants from causing buildup inside your engine’s intake manifold. Here’s how they work, and why you might want to install one on your own car.
A typical catch can plugs into a hose running from the top of your engine’s crankcase to the intake manifold. This hose relieves pressure in the crankcase generated by blow-by (when pressure escapes the combustion chamber by seeping past the piston rings). The problem is, this pressure relief hose allows oil and other nasty stuff from the crankcase to get into the intake manifold, where it doesn’t belong. These contaminants can build up inside the intake; when left unchecked, this buildup can hurt fuel economy and horsepower, and can even cause misfires.
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