quote:
Originally posted by i30krab:
Can I please get some feedback on this unusual pcv valve. Has anyone ever seen or used one??
http://www.rippmods.com/products/products_list_details.asp?menuid=3&productId=268
i30krab, let me start off by saying this, the explanation on their website is almost correct.
The stock PCV valve is, by design, a check valve.
In a normally aspirated engine the PCV system indeed properly vents the crankcase of blow-by, condensated water, excess fuel vapor in the oil, etc., etc. The air drawn out of the crankcase is replaced by filtered air through the PCV breather thats usually hooked up to your air filter housing.
The reason the PCV valve is designed as a check valve is to stop a backfire induced flame front in the intake manifold from making it to the crankcase where there's volitile vapors that can be ignited.
The other PCV design is a calibrated orifice with an incorporated sintered metal filter element, this sintered metal is what stops the backfire induced flame front, for obvious reasons this calibrated orifice PCV is not used in boosted engines.
On a pressureized/boosted engine, the PCV valve checks/stops the pressurized air so that the crankcase will not have pressure introduced into it.
If pressurized air is making its way into the crankcase through the PCV valve, then the PCV valve is defective and must be replaced.
When rippmods.com say:
"when the manifold is pressurized the excess blow-by gases now under pressure flow out of any part of the engine it can find such as the valve cover seal or gaskets, oil dip stick tubes, valve cover relief vent and various other “escape routes” the pressure manages to find."
They forgot to mention the PCV breather, it would be almost impossible to pressurize the crankcase due to the fact that the PCV breather is always open to atmospheric air and the diameter of the respective openings are different, PCV valve hose smaller/PCV breather opening larger. IMHO, the above quote sounds like a scare tactic to sell their $70 check valve.
I drive a 2005 Dodge Neon SRT-4 with the 2.4 liter turbo engine, I check my PCV valve to making sure that the internal valve is free, you do this by placing your thumb over the end of it with the engine running, you should hear the valve click when you remove your thumb, or if the engine is off, the PCV valve should rattle when shaken; to see if it'll hold boost pressure, I blow into the hose end of the valve, you should not be able to blow air through it, if it'll hold back my breath it'll hold back the turbo's boost.
I have high confidence in the stock PCV valve operating properly and will not be installing any other check valve in the system.
I have a writeup here on this very subject.
http://s6.invisionfree.com/Michigan_SRTs/index.php?showtopic=1089
I hope this helps.
Bill
