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Q: I need to isolate my intake from the PCV system

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My car is highly modified with a supercharger, complete exhaust and more. I've been advised to isolate my intake from the PCV system to prevent oil mist from flowing into my Supercharger and intercooler. To do this I've been told to run 2 catch cans vented to atmosphere. The first one from the Valve Cover and the second from the PCV valve on the crank case. My concern is that running vented to the atmosphere will create no vacuum in the system as it does in stock form. Is this problematic or will the engine run safely like this? One specialist in Miata's advises me to do this, and another claims it will cause problems with the bottom end and piston rings not seating correctly. I've scoured Miata forums and done google searches and keep finding conflicting information.

My car has 20000 miles.
My car has a manual transmission.

Hello. A high end catch can with a substantial stainless baffle will catch the oil vapors, as well as water, so there is no reason it or indeed sequential cans if you want to improve oil removal efficiency can’t be plumbed back into the intake creating a closed system. If you have a good catch can system, the amount of oil that might escape into the intake is extremely small and thus of no concern in your set up. Watch out in winter though, if you are in a cold climate. These cans will freeze solid due to water contained therein and that will block the flow of gases and cause pressure to build up within the engine as the blow by gases have nowhere to escape. Hope this helps.

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