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Re: Non-turbo engines don't have one-way pcv valves Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Sat, 4 Oct 2008 18:09:48 In Reply to: Re: Non-turbo engines don't have one-way pcv valves, SRS900, Sat, 4 Oct 2008 13:25:21 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Crankcase ventilation has been around since the beginning of Internal Combustion engines.
No piston ring seals perfectly, some combustion gases leak past and into the crankcase. Left unchecked, this will pressurize the crankcase, and eventually blow the seals out. This is not a good thing.
The crankcase connects to the valve train - oil in the valve train drains down to the crank, and any pressure in the crank passes up to the valves.
In the olden days - up to the mid 1970's - the crankcase would just vent to the atmosphere. This was usually just a 'crankcase breather' on the valve cover to let the oily gasses out. With the advent of emissions controls, oily, partially-burned combustion blow-by just can't be vented to the air. So that air gets ported into the intake manifold and gets burned again.
So every car has something like this, and burning those oily fumes is the way to go. Most cars have a PCV (Positive Crankcase Ventilation) valve. In some cars, it only opens when there is enough pressure difference between the intake and the crankcase - usually at idle or near closed throttle, when the intake is at vacuum.
With a turbo engine, you need a one-way valve so that under boost, you don't pressurize the crankcase.
posted by 76.219.9...
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