Sorry I am late to this thread. The issue has nothing to do with the checkvalve as long as a proper crankcase evac system is used, and to date, not a single manufacturer of FI systems seems to understand what is needed.
And what I see out there is most are deleting the evacuation function and only venting pressure to the air filter. Then there are some systems TOTALLY deleting the PCV system and running the fresh and foul sides together in one breathered can so that zero evacuation takes place allowing all the harmful combustion byproducts to accumulate in the crankcase contaminating the engine oil. Part of the blow-by all engines experience (the better the ring seat, the less blow-by) are compounds that will cause premature wear and damage to the internal engine parts over time if NOT evacuated as soon as they enter the crankcase before they can accumulate and contaminate the engine oil. As this wear happens over time, most will never associate the wear with the lack of a proper PCV system. Now, in that blow-by there is unburnt fuel, water vapor (released from the air in the combustion process), abrasive carbon particles (many to small in micron size for the oil filter to trap) and other damaging hydrocarbons, etc. In the crankcase sulfuric acid is also produced from a combination of these compounds and if this is not constantly, and completely evacuated (flushed by fresh in and foul out) it is going to accumulate in the crankcase settling into the engine oil and onto the internal parts (anyone that tears LS engines down can attest to the corrosion on the rocker arms and the needle bearing buckets on the drivers side when the valley cover vent is used on older LS engines that left the driverside stagnant).
So, there are going to be some unhappy C7 owners miles down the road that are installing the systems that delete all evacuation and tie the fresh and foul sides together into one can to vent.
And, now with the LT1 being Direct Injection, the intake valve coking issue is a new issue never before encountered by the LS crowd.
The solution? You must have a PCV/crankcase evacuation system that will retain the constant evacuation of these compounds, and any system that pressurizes the intake manifold under boost has to be modified as the intake manifold vacuum will only provide evacuation while in non-boost operation, and all systems to date we see are defeating the evacuation process by just running a vent line to the air filter.
The OEM PCV checkvalve is not designed to operate under 12-16# boost, so you must use a properly design checkvalve on the foul side to prevent boost pressure from entering the crankcase, and if used between the IM and the PCV valve, the OEM valve will not fail and stick. Then you most have an alternate evacuation source to switch to as soon as boost is detected. For this we have for the past 12 years used the inlet of the turbo/centri blower for this alternate suction (GM just began doing the same with the Cadillac ATS 4 cyl turbo with inlet suction fitting already cast/machined in). So, if you look at the RX system for the C7 Procharged, ECS/A&A systems you see we have the PCV system remain intact. We use the intake manifold vacuum to provide evacuation when in non boost with the primary checkvalve closing as soon as it detects any boost (protecting the OEM PCV valve preventing failure). We then tap into the head units inlet side for suction to continue evacuation as soon as in boost so when the primary valve closes, the secondary valve opens providing proper and continuous evacuation no matter if in boost or not. And the RX can is the only one that stops all the detectable oil from ingestion. Then, the cleanside separator provides the fresh side air uninterrupted and also stops and traps any oil from ingestion when pressure seeks the path of least resistance during the brief transition between non-boost and boost. So, you have zero pressure issues, you have a properly evacuating PCV system, and have maintained a EPA Emissions compliant system. The oil ingestion is stopped preventing detonation and intake valve coking, and no issues with these other compounds contaminating the engine oil.
Ask any questions on any part of this not clear...this is a subject that is so full of wrong solutions and misunderstood functions all over the internet and vendors jumping into the market with catchcans not designed to deal with any of this properly.
