phunk

A factory style PCV system allows oil vapor into the intake tract. An oil film will build up inside the intake tubing and intake manifold. This means you will consume a minuscule amount of oil through combustion, which according to the theory, will reduce the fuel octane.

That said, unless your engine is in terrible shape, the consumption is likely much too low to cause any perceivable increase in knock tendency. A looser fully built engine with tons of boost can have increased piston ring blow-by, increasing the flow through the PCV system. This is when I might start to consider a catch can, but I still would probably personally prefer to just go open on the ventilation to keep the engine bay less cluttered.

People with catch cans will observe what appears to be a significant amount of oil collected in their cans. I say if you put that oil back into vapor form and disperse it evenly through all the air the engine has ingested in that time, you would find it be nothing. There is also a question of how much of that oil collected is a direct result of eliminating the crankcase vacuum which many believe helps the rings seal, reducing crankcase vapors. If that's the case, it can make the catchcan a sort of self ful*filling* prophesy (see my pun there).

None of my belief is backed by scientific study. Just a matter of having always left it alone yet always having great success with my builds.

Great looking bay. Only thing i would change is one of the first mods I did to my 370z... rerouting the starter cable through the cowl instead of how the factory draped it over the timing chain covers.

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