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| PCV valve for boosted engines (Page 4/4) |
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zkhennings
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JUL 21, 04:14 PM
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In essence the oil may get dirtier from not evacuating the crankcase while also supplying it with fresh air. I imagine that could have negative performance effects over time.
Maybe I will retain my scheme of only feeding it to the intake pre-throttle body, but put a breather filter on one of the valve covers with a one-way valve so that instead of solely relieving crankcase pressure, the system will provide a fresh air source as well that the crankcase vapors cannot revert through.
My only issue with doing it the way that you have accomplished it is that at WOT where the most vapors will be produced, they will have to exit through the breather filter which could eventually get clogged and cause the crankcase to pressurize. Have you had any issues with this?
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pmbrunelle
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JUL 21, 09:07 PM
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| quote | Originally posted by zkhennings:
In essence the oil may get dirtier from not evacuating the crankcase while also supplying it with fresh air. I imagine that could have negative performance effects over time.
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That's the gist of it.
| quote | Originally posted by zkhennings:
Maybe I will retain my scheme of only feeding it to the intake pre-throttle body, but put a breather filter on one of the valve covers with a one-way valve so that instead of solely relieving crankcase pressure, the system will provide a fresh air source as well that the crankcase vapors cannot revert through.
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Pre-throttle body you'll get vacuum from the air filter restriction. The vacuum increases as airflow increases. So that setup will suck the most oily crankcase vapours at WOT... and you were concerned about the octane reduction due to oil. Octane matters most at WOT, but not at idle.
| quote | Originally posted by zkhennings:
My only issue with doing it the way that you have accomplished it is that at WOT where the most vapors will be produced, they will have to exit through the breather filter
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Yes, that's what it does.
| quote | Originally posted by zkhennings:
which could eventually get clogged and cause the crankcase to pressurize. Have you had any issues with this?
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I have observed a hint of crankcase pressurization when I found the dipstick popped out of its hole (perhaps raised 1 inch) a few times, though it did sometimes that with the stock 2.8 as well. However, it seems like the rubber on the original dipstick shrank, and it was no longer making contact with the dipstick tube. So, I made a small sleeve, and that gave the dipstick enough friction to hold:
The main issue I've had with the breather has been oil droplets (related to WOT, not calm driving) escaping the breather and landing on the valve cover. Originally, I had a smaller breather (perhaps 2" dia, 1" long). I switched to a larger breather (3" dia, 2" long), and the air/oil velocity slowed down enough that the pleating could catch the oil without it flying right through. For good measure, I also increased the diameter of the breather's inlet tube (in conjunction with a larger valve cover grommet), again to slow down the air blast.
The oil was stopped by the pleating, but then it would drip down onto the valve cover, so then I added the sock. So far I'm happy with this setup.
The breather filter hasn't gotten clogged, and it doesn't look like it would happens. Air filters in general don't completely clog, but I'm not driving through mud or anything.
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