Updated: November 15, 2009

LS-Man

PCV - Its Purpose, Pros and Cons of Delete

PCV is the Positive Crankcase Ventilation system (valve) has been in cars for decades for several reasons including a mandatory requirement by governing bodies.

There are several descriptions on the internet in detail as to what they do so I won’t bore anyone with its function. Ill just include one good picture that I found.

Let’s just jump right in to the Pros and Cons of a PCV system both keeping a functional one and deleting one. Feel free to email me any additional suggestions info@trafficjams.ca

Keeping a PCV system (Stock Setup)		Delete PCV
Pros	Cons	Pros	Cons
Keeps Oil Clean of contaminants	Engine Pulls oil into intake causing possible detonation – reduce octane rating	Eliminates possible detonation due to oil in combustion air (particle or mist)	Oil life is greatly reduced
Oil life is greatly improved	Over time coats valve stems, piston crowns and spark plugs	Keeps Intake tract clean	Possible to have too much pressure and cause engine seals to leak
Environmentally proper	Air filter / MAF sensor contamination after engine shut-off	Keeps valves clean	Oil smell is possible in cabin
It’s a mandatory item by governing bodies to pass emissions		Neat and tidy engine bay	Polluting the environment
Reduces Hydrocarbon Emissions			Causes rapid rust and contaminants on bearings and crankcase
Relieves stress on seals

It seems the PCV system is an important part of basic engine function. Now to get to the debate; lets look at weather to delete it or not.

We should suggest keeping the PCV and keeping that oil breathing fresh, but want to remove that nasty film buildup in the intake tract. Catch cans (oil separators) are available some work, some don’t and they can get pricey.

What about just plugging up the intake and PCV hoses and putting a tiny filter on the valve cover? – Basically deleting the PCV. That’s fine and all, but the crankcase now has to ‘push’ the blow by and air out of that little filter. To run this type of setup properly you must use a Crankcase Ventilation Vacuum pump, causing the same effect as vacuum from the manifold. These pumps are costly and require a bit of wiring and plumbing to work. This is your only option if you do not want any connection what so ever to the intake tract. This does not meet emission requirements either.

In the end, some sort of ventilation is a must, period. To just simply delete and plug up the PCV system is not an option.

Best description found on the forums…

Merely defeating PCV leaves you with no way to remove water vapor from the crankcase. Since the early part of the last century, the effects of this have been well known. Brown froth, sludge, acid formation, and accelerated engine wear. Prior to the introduction of PCV around 1960, cars had a draft tube that allowed the air moving past it to create a slight vacuum that evacuated crankcase gasses and vented them to atmosphere. While first employed as an anti pollution measure, it was quickly found that using engine vacuum to clear crankcase vapors was much more effective than a draft tube, and allowed better reliability and longer service intervals.

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MR

LS Man