Why specifically are oil catch can(s) needed

[stanglife]

If you apply historical knowledge about how an engine works, using a catch can sounds pretty convincing (yes, I'm arguing both sides of this because I think there are valid concerns). (General enthusiast car knowledge here) An engine under constant load and high-RPM is 1 - going to build more crankcase pressure due to blowby and 2 - cause more windage which typically gets sucked up by the PCV system for recirculation/combustion.

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[JAJ]

I've tried doing my research. I think I understand the following:

- oil catch cans minimize crankcase aerosolized oil from getting put through the intake system,
- this is not related to oil usage issues with some of the Voodoo engines (or at least significant oil usage, which seems to be an oil control piston ring issue), and
- for most, a passenger catch can collects some oil, a driver catch can very little.

Since the combustion chamber will already have a film of oil on the walls, I assume the thinking from keeping oil from being introduced into the intake is:

- maybe prevention of eventual sludge formation in the intake manifold runners,
- maybe prevention of crud accumulation on the intake valves,
- maybe prolonging spark plug life, and/or
- maybe slightly more power because of more perfect combustion without the oil being present.

Most of the information I found seems to point to the oil collected as the reason for the catch can, without engine tear down or boroscope pictures showing engines with and without catch can use. (The "see, here's the oil" with the assumption that said oil is damaging.)

Can anyone point me to data driven (versus opinion driven) reasons why catch cans are important to either prolonging the life or performance of the Voodoo (or other engines). I don't have any issue installing at least the passenger side catch can, but I'm looking for the reasons why it is a good idea.

Let's get down to basics: I have one on my GT350 because Ford Performance recommends it for track use.

The best explanation I've found for why they're useful is from Wikipedia: "Another issue that has been raised as a possible problem with allowing oil vapor into the intake is the chance of pre-detonation … This has become more of an issue as more and more cars have started to run high boost levels and high compression ratios."

While oils are formulated with less deposit-forming chemicals than they used to be, oil carried into the combustion chamber can still form deposits on the pistons and valves. Some oil is inevitable because it's on the cylinder walls and valves guides, but that doesn't change the fact that diverting oil that can be diverted is a good thing.

 

[Woody25]

Small investment for a relatively expensive car, so I decided to do both sides for a peace of mind.

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