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Rocker cover breather hose and PCV 

 

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 Post subject: Rocker cover breather hose and PCV
Posted: Mon Dec 26, 2005 10:35 pm 
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Just a few quick questions about the breather hose on the back of the rocker cover nad the PCV on the front.
Am I right in that the PCV needs to be connected into the intake manifold as it needs the vacum and that to function properly?
and the rear breather hose doesn't need to be (i.e. can a small filter be placed on it instead)?

 

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 Post subject: Re: Rocker cover breather hose and PCV
Posted: Mon Dec 26, 2005 11:00 pm 
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twr7cx wrote:
Just a few quick questions about the breather hose on the back of the rocker cover nad the PCV on the front.
Am I right in that the PCV needs to be connected into the intake manifold as it needs the vacum and that to function properly?
and the rear breather hose doesn't need to be (i.e. can a small filter be placed on it instead)?


if you want it to be legal, no you can't put a filter on it. it needs to be conected to the TB.
if you are worried about oil vapor droping the octane rating of the feul run it through an oil catch can first then to the tb

 

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Posted: Mon Dec 26, 2005 11:04 pm 
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were ignoring legalities at this stage, speaking hypothetically.

just trying to find out if either the PCV or the rear breather actually require the vacum from the intake manifold to properly function.

also, how much oil do these spit out ? do both spit oil out? because if there spitting oil out then a filter as in the picture may not be such a good idea as it'll just get drowned in oil. but if there oil venting gases/breathing should be fine?

i was thinking little filter for the rear and oil catch can for the front - but that's on my previous assumption that the pcv spits out oil with the gases while the rear one only breathes.

 

 

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Posted: Mon Dec 26, 2005 11:32 pm 
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i thaught all the front one does was create vacume with the valve. without it it ideles too high and lumpy
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Posted: Mon Dec 26, 2005 11:42 pm 
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i wouldn't have thought the PCV could effect the idle as the PCV is opened when the pressure in the rocker cover gets to a certain point and then all it does it relieve the pressure by opening the valve and spitting out the gases and oil down the pipe and into the inlet manifold is then send down teh manifold with the air and into the combusion process and out the exhaust...
actually it may be effected at idle as there would be a strong suck down the line which could suck the pcv open? but say under boost there would be a strong blow which could stop the pcv from opening unless the pressure in there is greater than the pressure in the inlet manifold.

 

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Posted: Tue Dec 27, 2005 12:09 am 
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PCV is not opened by pressure in the rocker cover/crankcase, it is opened by intake vacuum. Its primary design is to circulate fresh air through the crankcase to reduce emissions and oil contamination. It will also help vent blowby pressure (along with the breather pipe).

PCV requires intake vac to work properly, and it does function at idle as well as full throttle. The breather pipe does not have a vacuum supply (if it did have an intake vac supply it would actually cause problems) and you could just use a filter instead (although it probably causes more problems then good).
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Posted: Tue Dec 27, 2005 6:05 am 
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Posted: Tue Dec 27, 2005 4:40 pm 
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EDXR8 wrote:
The breather pipe does not have a vacuum supply (if it did have an intake vac supply it would actually cause problems) and you could just use a filter instead (although it probably causes more problems then good).


any chance you can elaborate on these problems?

quote="EDXR8"]PCV is not opened by pressure in the rocker cover/crankcase, it is opened by intake vacuum.[/quote]
so any idea what happens under boost to it?

 

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Posted: Tue Dec 27, 2005 4:51 pm 
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The breather pipe is designed to let the fresh air into the crank case, it then circulated through the crankcase mixing with unburnt gasses and is sucked back out the PCV pipe. If the breather pipe is hooked up to an intake vacuum supply then it won't let the free flow of air into the crankcase, it just cause a vacuum in the crankcase no the constant flow in and out that the PCV system is designed for.

Under boost the PCV valve is forced closed (by the boost pressure in the intake manifold), but blowby can still escape however via the breather pipe. Because turbo/blown engines normally have more blowby, and the PCV system stops working under boost, you often see turbo/blown engines having multiple breather pipes.
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Posted: Tue Dec 27, 2005 6:56 pm 
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wicked thanks for the info.
so were do all the extra multiple breather pipes that boosted engines have run to? catch cans or elsewere in the intake piping/manifold?

 

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Posted: Tue Dec 27, 2005 7:05 pm 
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For legal reasons they should vent back into the intake piping, and if you are worried about oil in your intake charge then a catch can can be installed. Some people just vent to atmosphere (can't really do that on MAF based cars though), but I think its just as easy to recirculate it, at least then you keep the police and hte environment happy.
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Posted: Wed Dec 28, 2005 12:08 pm 
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Is there anything that needs to be changed if adding a turbo? Im turboing my ef and this area has got me completely puzzled.

 

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Posted: Wed Dec 28, 2005 1:48 pm 
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bogan393 wrote:
Is there anything that needs to be changed if adding a turbo? Im turboing my ef and this area has got me completely puzzled.


For forced induction you have to make sure the breather hose is relocated before the turbo otherwise the boost will preasurise the crankcase. You can leave the PCV hose/valve alone, just make sure the valve itself is in good condition and seals properly (i fitted a one way valve in the PCV line just to make sure).
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Posted: Wed Dec 28, 2005 3:23 pm 
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go out and take the valve out. start it up and get someone to hold there finger over the hole where the valve is ment to be. then get them to take there finer off and you will notice the idle goes all up the s**t
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