z-ya Posted September 7, 2011 Share Posted September 7, 2011 Now that is a pile of garbage..... First get the car to run and drive reliably, then worry about longevity. Now as far as the lack of a PCV effecting performance, I've never run one on a race car, and never had problems with performance or crankcase ventilation. PCV is mainly for emissions. Quote Link to comment Share on other sites More sharing options...
ktm Posted September 7, 2011 Share Posted September 7, 2011 (edited) I drilled and tapped my vent tube coming out of the engine to fit a threaded PCV valve. I took the tube down to my local parts store and spent 10 minutes perusing their selection, matching up the diameter of the tube to the diameter of the PCV valve. I then verified the direction of the valve and all was well. Quote from six_shooter: the PCV valve is really quite important to the proper operation and logevity of an engine. A proper system will will crankcase fumes into the engine to be burned off, clearing damaging fumes. These fumes acn deteriorate the gaskets, and leave excess pressure in the crank case, without the PCV system connected. At higher RPM, the PCV system will, when connected properly create a small vacuum, or at the very least less pressure in the crank case, allowing the pistons to move down the bores easier, helping create more power than without the PCV system connected. If you are boosted, such as in this application, the PCV valve does not function. Well, it is functioning as intended. The valve will close under boost so that the crankcase is not pressurized by the manifold. The PCV valve only functions under manifold vacuum conditions such as cruising. Edited September 7, 2011 by ktm Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 7, 2011 Share Posted September 7, 2011 KTM, that is incorrect and a gross oversimiplification of how the Nissan PCV Valve works! The PCV will indeed close on-boost. At that time, the differential by the inlet filter being drawn on by the turbo evacuates the blowby to prevent crankcase pressurization... In this aspect, it is more to prevent nuisance oil leaks than anything else. A plugged crankcase WILL build pressure, and WILL start pushing oil out every orifice, gasket, and seep point possible. In the old days, the "Road Draft Tube" was where your blowby went. Later, PCV was introduced to contain the vapors, true enough, but there is positive compelling evidence on the effects of positice ventilation and vacuum in the crankcase affecting windage and power levels. It promotes ring sealing to be sure, even top fuel dragsters acknowledge this and run vacuum pumps or vac-u-pan systems to aid for this effect. But the turbo operation (as well as some other modes where the Nissan PCV acts more as a limiting-flow-control valve--it's not just open or closed, it has intermediate functional points where it limits the vacuum pulled on the crankcase to prevent deluging the intake with excessive oils...) simply lets the crankcase vent through the air makeup line on the valve cover to the intake tract's lowest pressure point to insure there is no pressure building up in the crankcase EVER. Pressure in the crankcase (even as little as 4" H2O will cause MASSIVE leakage from front and rear seals. Those seals are designed to keep DIRT OUT not OIL IN! (That is mostly accomplished by the SLINGERS, which are aided in oil return by air passing over the seals in towards the gearbox...) The PCV not only acts as a check valve in Turbo Application, it regulates vacuum applied to the crankcase, and acts as a flow diverter valve depending on manifold vacuum presence. This is why it is critical to have it cleaned and operating freely. We are talking about very low pressure ratios which cause the valve shuttle to restrict or stop flow altogether. Notice at WOT (without a turbo) that the fumes come out the valve cover? Why? Because the PCV is closed at that time. And on snap-throttle closing from WOT---closed again to open in a modulating action to regulate vacuum spikes to the crankcase which could literally draw oil up the pipe like a straw! It's not as simple as people make it out to be. It does work... You want a simple system, get a Corvair with a hole in the sucker tube and see how well it works when it plugs with sludge... Quote Link to comment Share on other sites More sharing options...
z-ya Posted September 7, 2011 Share Posted September 7, 2011 I stand corrected. It makes sense to use a PCV in any boosted application as a check valve to prevent over presurizing the crankcase. Quote Link to comment Share on other sites More sharing options...
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