PCV Valve

[scottravenhill]

Has anyone changed theirs? Honda reccomend check and replace if necessary on every 12k service (not 6k interim)

[wezza9]

ok what is a PCV valve ?

[scottravenhill]

positive crankcase ventilation valve

The Positive Crankcase Ventilation valve, or PCV valve, is a variable-restriction valve that assists with the continual evacuation of gases from inside a gasoline/petrol internal combustion engine's crankcase.

As an engine operates, high-pressure gases are contained within the combustion chamber and prevented from passing into the crankcase (containing the crankshaft and other parts) between the side of the piston and the cylinder bore by piston rings which seal against the cylinder. However, some amount of gas always leaks past the piston rings into the crankcase. This amount is very small in a new or properly rebuilt engine, provided that the piston rings and cylinder walls are correctly "broken in", and increases as the engine wears. Scratches on the cylinder walls or piston rings, such as those caused by foreign objects entering the engine, can cause large amounts of leakage. This leaked gas is known as blow-by because the pressure within the cylinders blows it by the piston rings. If this blow-by gas could not escape then pressure would build up within the crankcase.

Before the invention of crankcase ventilation in 1928, the engine oil seals were designed to withstand this pressure, oil leaking to the road surface was accepted, and the dipstick was screwed in. The hydrocarbon rich gas would then diffuse through the oil in the seals into the atmosphere. Subsequently, it became an emissions requirement as well as a functional necessity that the crankcase have a ventilation system. This must maintain the crankcase at slightly less than atmospheric pressure under light load conditions and recycle the blow-by gas back into the engine intake. However, due to the constant circulation of the oil within the engine, along with the high speed movement of the crankshaft, an oil mist is also passed through the PCV system and into the intake. The oil is then either burned during combustion, or settles along the intake tract, causing a gradual build-up of residue inside the inlet path. For this reason many engine tuners choose to replace the PCV system with an oil catch can and breather filter which vents the blow-by gases directly to atmosphere and retains the oil in a small tank (or returns it to the sump), although this technically fails to meet most engine emission legislation.

[james]

[scottravenhill]

so yeah anyone replaced these before or changed them for breathers as i quote

"many engine tuners choose to replace the PCV system with an oil catch can and breather filter which vents the blow-by gases directly to atmosphere and retains the oil in a small tank"

[james]

well the catch can is supose to be good for your motor

i am gona get one

but no direct answer

[scottravenhill]

i think its the little hose that is on the top of your rocker cover? i think you just replace that with a breather filter, dont understand how the can 'catches' the oil after it blows the gas into the engine bay, unless you house the breather inside the oil catch can???

[james]

do not put the filter on the top of the rocker cover outlet, the fumes will be very very bad for you as the will get in through the air fents and kill you

and the oil will seep out of the filter anyway henc catch caN

[scottravenhill]

yeah i saw a pic of someones engine bay and they had it on there. just dont see how the catch can catches it unless it has a vacuum inside it

[james]