Quote:
Originally Posted by citizenboyo
Sorry, Might be a dumb questions but what exactly do oil catch cans do? Do they prevent gas from recirculating into the engine or is it engine oil?
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It's oil. Or rather, oil particulates. Oil vapors in the head and block are routed through the PCV valve, back to the intake, so they can be ingested and burned, rather than vented to atmosphere (for emissions/EPA compliance). Normally not a huge issue, since the fuel would spray the valves on the way into the engine, keeping them mostly clean. With the newer Direct Injection systems, the injector sprays into the cylinder itself (kind of like how the spark plug sits). So, add together oil vapors, hot valves, and lack of cleaning fuel spray, the oil and other carbon byproducts begin collecting and burning onto the valves (similar to oil coking). This buildup restricts airflow, changes the air flow pattern into the cylinder, and eventually begins to cause misfires. In extreme cases, the crumbling bits can come loose and ruin a valve seat or bend a valve.
So, after that novel, the oil catch can is installed inline with the PCV system. The air with oil vapors goes through the can, and through a series of baffles. The oil (and moisture I believe) is allowed to condense back to liquid form (or at least get trapped in the can/baffles). Every so often, just pull the can (some have a screw on can like an oil filter) and empty it out. By eliminating and/or reducing the oil vapors going down the intake, the less buildup that will form on the valves. Also helps to keep the rest of the intake cleaner (throttle body, temp and airflow sensor, etc). The charge pipe and intercooler are known places where oil will condense, and make a mess during disassembly.