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A lot folks modify or disable the PCV system of a performance care engine. I suggest that before you do so, try to understand the purpose and function of the system:
The purpose of Positive Crankcase Ventilation is not just to let the blowby fumes out of the crankcase, and prevent the engine seals from getting blown out by the pressure, but also to continually purge the crankcase with fresh filtered air to remove the blowby gasses (water vapor, CO2, CO, NOx, and Hydrocarbons). These gases mixing with the oil droplets (and oil mist) in the crankcase at high temperatures degrade the oil, tending to form acids and sludge. This works at part-throttle, when there is significant vacuum in the intake manifold, through the PCV valve, which functions as a flow regulator. It is more restrictive when the vacuum is high. In a well-designed crankcase ventilation system, when crankcase fumes are pulled into the intake manifold through the PCV valve, the make-up fresh air comes in through the large hose at the valve cover and that air flow sweeps the blowby gasses out of every nook and cranny of the crankcase. In not-so-well designed systems, the fresh air flow only partially cleans out the crankcase fumes. These engines, and ones with really rudimentary CCV systems (no PCV valve), the engines tend to sludge-up and otherwise degrade the oil more quickly than a good modern engine. That is one reason why in many cases you can get normal engine life with 7500 to 10000 mile oil change intervals. If you do not hook up the PCV valve to the intake manifold, as it was designed, you are not actually getting continual crankcase ventilation.
When power level is higher, the blowby gas volume is higher, and intake vacuum goes away; the PCV may shut (it is also a one-way valve) and all of the blowby gasses flow out the upper hose attached to the valve cover. You don’t get crankcase ventilation, just a way for the blowby gasses to exit the crankcase without blowing out your oil seals.
So if you really do not want your high-power blowby to get re-breathed into you engine, you can get away with hooking that hose to a filter and catch/can oil seperator. The only real consequence is that you will be dumping raw exhaust pollutants into the atmosphere at high load. If you do not plumb the PCV valve properly, you might as well remove it and you will not actually get crankcase ventilation.
If you want to make best use of a catch-can, put it in the large hose between the valve cover and the air cleaner hose because this has the highest peak flow-rate and on most engines, the oil separation isn’t that great due to the high velocities in this path. Also, as an engine wears, this gets worse. The reason why this isn’t usually a problem for production engine is that most engines only get very brief use near full-power. The hose to the PCV valve will benefit less from a catch-can (for most engines) because the flow rate is very limited by the valve and it is easier for the OEM to design an adequate oil separation device for this low flow rate and gas velocity.
On a really healthy engine with a good separator built into the valve cover, you might collect more oil in a catch-can in the PCV valve loop.
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