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How does the PCV work in boosted applications? 

 

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Posted: Sat May 20, 2006 4:02 pm 
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concorde wrote:
tickford_6 wrote:
you guys seem to be forgeting that the PCV is a valve and it will close under boost. and operate the same as it always did. the only thing i would recomend is the use of the early type one, steel not plastic

the rocker breather at the back of the head is the one you need to worry about. thats a simple fix though, from the rocker cover to oil catch can to intake piping pre-boost (infront of turbo/blower


when is the crank case going to pressurise and need to be vented? when the engine is running max boost, when the PCV needs to open, which is when the valve won't open becasue it has boost pressure pushing it closed.

Use a catch/breather can.


in that case the rocker breather you have moved to infront of the the turbo, s/c will vent the crank case.

remember when in an NA situation the most crank case pressure is at FULL THROTTLE and the PCV is closed then aswell

a little reaserch on the topic of the PCV with google will help a few people here.

 

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Posted: Sat May 20, 2006 8:30 pm 
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Blu Falc wrote:
also known as a catch can


NO NO they are not the same, one is a can, the other is built to seperate oil from air.

The one I had made uses centrigugal force to spin the oil out then it also has angled baffles inside the centre tube to remove oil vapour, you can vent this back in before the turbo it will remove 95% more than a catch can. Also it has a drain back so its self sufficient, most cans you have to empty.

I choose not to run a PCV, the benefit of running one is that you remove the flammable gasses from the crankcase, the vent only system only lets out the excess gasses it doesn't actively scavenge them, which is an advantage, but something you typically only see on stock'ish cars.

The deciding difference between the oil air seperator and a catch can is usually the cost, the catch can is cheap(ebay) and requires few lines/fittings, the seperator costs heaps more usually needing to be custom made, and needs 3X more lines/fittings.

 

 

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Posted: Sat May 20, 2006 8:54 pm 
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ltd351T wrote:
Blu Falc wrote:
also known as a catch can


NO NO they are not the same, one is a can, the other is built to seperate oil from air.

The one I had made uses centrigugal force to spin the oil out then it also has angled baffles inside the centre tube to remove oil vapour, you can vent this back in before the turbo it will remove 95% more than a catch can. Also it has a drain back so its self sufficient, most cans you have to empty.

I choose not to run a PCV, the benefit of running one is that you remove the flammable gasses from the crankcase, the vent only system lets out the excess gasses it doesn't actively scavenge them, the PCV is an advantage on stock cars with minimal blowby, but something you typically only see on stock'ish cars, anything with larger piston to bore clearance the PCV will be a negative thing as the engine would be consuming excessive oil. At least thats how I think it all works I could be wrong.

The deciding difference between the oil air seperator and a catch can is usually the cost, the catch can is cheap(ebay) and requires few lines/fittings, the seperator costs heaps more usually needing to be custom made, and needs 3X more lines/fittings.

 

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Posted: Sat May 20, 2006 10:57 pm 
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my mistake, when i made one i used steel pipe (4") and had internal baffles and packed with stainless steel wool. worked well and it would drain itself.
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Posted: Sat May 20, 2006 11:21 pm 
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I've got one that has a bolt in the bottom just undo it to drain. It's got two fittings at the top for hoses, adn i've filled it with steel wool. It's got a level indicator on the side. And then at the top there's an oil cap, going to replace that with one of those breather oil caps, and run the PCV and rear rocker cover breather into the can.

 

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Posted: Sun May 21, 2006 1:00 am 
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On my V8 I added 100mm alloy tube so movng pcv higher making it harder for oil to be drawn into manifold...The hose from oil filler was disconnected and joined to filter via seperator.... I have breathers on boh rocker covers they vent to filters also... A pcv keeps oil cleaner and helps keep condensation out of oil..

 

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Posted: Sun May 21, 2006 12:06 pm 
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Blu Falc wrote:
my mistake, when i made one i used steel pipe (4") and had internal baffles and packed with stainless steel wool. worked well and it would drain itself.


sounds like a good design

 

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Posted: Sun May 21, 2006 10:04 pm 
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I don't run a PCV on mine.

I have been meaning to set it up better but have been told not to run it directly to the inlet of the blower.

Down side to my set up is the oil vapour in the engine bay :(
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Posted: Sun May 21, 2006 10:10 pm 
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LTDHO wrote:
I don't run a PCV on mine.

I have been meaning to set it up better but have been told not to run it directly to the inlet of the blower.

Down side to my set up is the oil vapour in the engine bay :(



your PCV is always plumbed into the intake manifold. it never needs to be moved.

 

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Posted: Sun May 21, 2006 10:21 pm 
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tickford_6 wrote:
LTDHO wrote:
I don't run a PCV on mine.

I have been meaning to set it up better but have been told not to run it directly to the inlet of the blower.

Down side to my set up is the oil vapour in the engine bay :(



your PCV is always plumbed into the intake manifold. it never needs to be moved.
Who said I was moving it?
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Posted: Sun May 21, 2006 10:34 pm 
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LTDHO wrote:
I don't run a PCV on mine.

I have been meaning to set it up better but have been told not to run it directly to the inlet of the blower.



by the sounds of that its been moved already

all i'm saying is there is never a need not to have conected. forced induction or not the factory arrangment is correct

 

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Posted: Sat May 27, 2006 7:45 pm 
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tickford_6 wrote:
twr7cx wrote:
So your saying rerout the rear breather, but PCV is fine to be left?



change it to the EB style steel PCV, but yes it will not flow air into the engine.
the boost will close it


This is correct. The positive pressure on the manifold side of the PCV will close it when on boost.

The plastic PCV's end up breaking in situ and the bits end up floating about inside your engine. - I had this happen recently.

The steel ones are the go.

The catch cans are best plumbed to the back of the rocker cover and then to make it legal run another line to the mouth of the turbo piping so it has light suction on it. This is a closed system and will pass engineering.

 

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