R56 Most liked posts in thread: Catch can Install and blind caps

Like Dave, I ran the BSH CC with a BSH Dual Tap blocking the rear PCV port. I used one tap for a boost gauge and the other for a Forge BOV/Diverter. I had it installed for about three years and it was still working fine when I traded the car. This is a picture of my setup.

 

Your mechanic does not understand how the MINI's PCV system works, it is different from most cars. The N14 engine has two PCV valves. The rear PCV valve, to the throttle body, opens when the intake manifold is in vacuum, this is when the turbocharger is not supplying boost. It closes when the turbocharger is supplying air pressure to the intake manifold,think of it as a one way valve.

When the turbocharger is supplying boost it causes a slight negative pressure on the PCV valve to the turbocharger inlet, that and a small build up of crankcase pressure, opens the driver's side PCV valve and allows the turbocharger to draw a vacuum on the crankcase.

When you block off the rear PCV valve to the throttle body, all of the PCV valve function is performed by the PCV valve to the turbocharger inlet, this does not hurt anything as the valve is very sensitive and it will not allow crankcase pressure to build up. Sometimes that valve will fail closed, this will cause the crankcase pressure to build and cause oil leaks at the crank seals and the head cover. a new head cover will solve the problem.

I have been running my N14 engine with the PCV valve to the throttle body blocked off and an oil catch can on the PCV line to the turbocharger inlet for nine years with no problems. The PCV line to the throttle body is the principle source of oil mist to the backs of the intake valves where it burns and chokes off the intake ports. That is why you put an oil catch can on the PCV line to the turbocharger inlet, to help keep oil out of the intercooler.