PCV system
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| − | ==Why | + | ==Why a PCV system is needed== |
Positive Crank Case ventilation is needed to help remove the acidic gaseous buildup inside the crank case. This is caused by combustion gas blowby around the rings as well as fumes released as the oil gets hot. | Positive Crank Case ventilation is needed to help remove the acidic gaseous buildup inside the crank case. This is caused by combustion gas blowby around the rings as well as fumes released as the oil gets hot. | ||
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Before the PCV system road draft tubes were used. This basically vented the gasses directly to the atmosphere. This was major source of smog in big cities and an initiative was launched to solve this. GM invented the PCV system and "gave" it to other manufacturers to use. This was the first emissions control device on automobiles and it drastically reduced the smog problem. | Before the PCV system road draft tubes were used. This basically vented the gasses directly to the atmosphere. This was major source of smog in big cities and an initiative was launched to solve this. GM invented the PCV system and "gave" it to other manufacturers to use. This was the first emissions control device on automobiles and it drastically reduced the smog problem. | ||
| − | ==Typical | + | ==Typical configuration and components== |
There are only a few components involved in the PCV system. | There are only a few components involved in the PCV system. | ||
| − | * A breather is located in | + | * A breather is located in one valve cover through a rubber grommet. This allows fresh air to enter the engine. There are two popular ways to do this. |
| − | ** A tube that connects | + | ** A tube that connects the valve cover to the air filter. |
| − | ** | + | ** Or a small air filter/breather that pushes directly into the hole in the valve cover. |
| − | * The PCV valve itself is located on top of the | + | * The PCV valve itself is located on top of the valve cover opposite the one with the fresh air intake, usually through a rubber grommet. |
| − | ** The area inside the valve cover where the grommet is located should be baffled. This helps to avoid oil getting sucked into the valve. | + | ** The area inside the valve cover below where the grommet is located should be baffled. This helps to avoid oil getting sucked into the PCV valve. |
| − | * A rubber hose that connects the PCV valve | + | * A rubber hose that connects the PCV valve a vacuum source, usually at the front of a carb or into the plenum area of the intake, not routed into an individual intake runner. |
| − | * This setup allows fresh air to enter one side of the engine, go through | + | * This setup allows fresh air to enter one side of the engine, go through crankcase, and be introduced into the intake tract. |
| − | You should avoid attaching the breather tube and PCV to the same valve cover. This will not vent | + | You should avoid attaching the breather tube and PCV to the same valve cover. This will not vent enough of the combustion gases. |
==PCV valves for modified engines== | ==PCV valves for modified engines== | ||
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==DIY catch can== | ==DIY catch can== | ||
| − | *Catch can if used need at least a 3/8" connectors and baffles inside. Without some sort of baffle inside the catch can the engine will suck up some oil. Avoiding oil is | + | *Catch can if used need at least a 3/8" connectors and baffles inside. Without some sort of baffle inside the catch can the engine will suck up some oil. Avoiding oil is important because it will create carbon deposits on valves, pistons, and combustion chambers which hurts performance and can cause preignition when the carbon gets hot. Oil vapors also are a source of detonation which can destroy pistons. |
The catch 'bottle' below is made from an air compressor oil separator, it is a cheap alternative to commercially available off the shelf units. | The catch 'bottle' below is made from an air compressor oil separator, it is a cheap alternative to commercially available off the shelf units. | ||
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The LQ4 6.0L crate engine from GM comes with a fixed orifice in the valve cover. The paperwork says to throw the original PCV valve away and connect the hose to the nipple. It appears they are finding the correct size orifice for the engine vacuum and are no longer using a valve. Perhaps a small inline needle valve to adjust crankcase vacuum flow might be the ticket. Not too much to cause a major leak, just enough to evacuate the crankcase. | The LQ4 6.0L crate engine from GM comes with a fixed orifice in the valve cover. The paperwork says to throw the original PCV valve away and connect the hose to the nipple. It appears they are finding the correct size orifice for the engine vacuum and are no longer using a valve. Perhaps a small inline needle valve to adjust crankcase vacuum flow might be the ticket. Not too much to cause a major leak, just enough to evacuate the crankcase. | ||
| − | A fixed orifice system may not work in all applications, especially forced induction. The pintle valve acts a check valve allowing pressure to move one direction. Likewise, the | + | A fixed orifice system may not work in all applications, especially forced induction. The pintle valve acts a check valve allowing pressure to move one direction. Likewise, the pintle valve system acts like a spark arrestor, preventing any combustion gasses from entering the valve cover should a backfire occur. |
==High tech adjustable PCV== | ==High tech adjustable PCV== | ||
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[[Category:Undeveloped articles]] | [[Category:Undeveloped articles]] | ||
[[Category:Undeveloped Engine articles]] | [[Category:Undeveloped Engine articles]] | ||
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