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Oil breather - why you should NOT replace the line by one of those tiny filters

startrack

Formerly type_r_lover
Messages
2,079
I was looking at some information on the oil breather "issue".

Basically you don't want to keep it the way it is, as the oil foam that gets into your intake messes up the Octane level of the mixture you are burning.... however as it is a closed vacuum line, surely you dont wanna keep it open either.

I found that ultra long post on ephatch that tells you all about it.

http://www.ephatch.com/forum/showthread.php?t=129135


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I was wondering how many people can figure out what is wrong in this pic?
filterkn2.jpg




It is the valve cover breather filter.

Adding just a filter is rather a bad idea for a NA motor. You would now induce humid air into the motor as the PCV system is supposed to be sealed. The location that this filter is located at, is supposed to see a draw from the intake, applying a small vaccum to the valve cover. Thusly the addition of this filter is having the same affect as creating a vaccum leak(down thru the oil drains in the head, thru the block,the PCV valve and directly to the IM).

If you have a oil seperator/catch can between the PCV valve and IM you will find the oil in it all foamed up, with a pale chocolate color indicating moisture in the motor.

This is all from first hand experience.

I wanted to post this up as I seen two cars today with this cool looking filter installed and could see this becoming a "cool cheap mod".

And yes I had one of these cool filters installed for all of 20 minutes.

Quote:
Originally Posted by squeak04si
i dont see the big problem? i dont have anything at all on mine. my valve cover breather is just open. the purpose of it is to blow out the excess vapors built up in the head. thats why there is a radiator coolant adapted to the line to burn off the oiy vapors before it enters the intake pipe. the intake sucks the air from the valve cover. thats why sometimes you will find oil residue in the throttle body or intake. my car has never had any problems and its just left open to the atmosphere, it just constantly blows to the atmosphere

The majority of vapors go OUT thru the PCV valve, and a very little from the valve cover breather tube(only at high rpm's).
There is a vaccum applied by the intake to the VC and as the crank rotates there is a pulsing action exerted onto the air at the VC. The heated tube warms the air pulsing there to prevent condensation from forming inside the motor. The vapors, along with air drawn from the intake are drawn thru the motor, out thru the PCV valve and into the intake. If there is no resistance applied(from the intake) to the air from entering the VC then the air goes straight thru the engine block and out thru the PCV valve. Creating a vaccum leak you will not hear.

Without a even a filter there you will allow all sorts of CRAP to be drawn into the VC, add some oil and you are now wet grinding all the mechanicals in the head!!!

It is your engine to destroy, I am informing others to not make your mistake. Hook up Kpro and check what your MAP is reading without the VC connected to the intake and then check it with it installed and you will see the difference.

Proper crank case pressure is required for the rings to seal and wear properly.

I would imagine that another side affect of the filter would be some added oil "consumption" thru the PCV/IM.

Quote:
Originally Posted by squeak04si
well air is blows out my vc even at idle. my vaccuum always reads around 20-22 as it is. i have the revhard kit and it doesnt come with a spot for this to be hooked up, so where would they be expecting you to hook this up then?

I would add a catch can and plumb it in between the filter and compressor.

With a NA motor at least, having this line from the VC to the intake disconnected will cause a vaccum leak as you change the volume and speed of the air going thru the intake/motor. Almost like a stumble or a feeling of being restrained/held back.

Quote:
Originally Posted by squeak04si
could i just tee it in between the pcv and mani? or could i tee it into the brake line going into mani?

Dont do anything to the brake booster line.

It should not be connected to the PCV-IM line either. It must be connected to the intake prior to the TB and in your case with FI, also prior to the compressor.

Without having a air box installed, adding a catch can there is no problem. Summit racing has one for dirt cheap.




Quote:
Originally Posted by squeak04si
how am i gonna run into the intake before the compressor? there is no spot for it? and why would revahrd and cybernation make a kit that wouldnt have a spot for this to hook up?

I dont have an answer for you on that, perhaps they along with many others do not understand how that impacts the PCV system.

All SRI's and CAI's have a spot to hook up the tube from the VC.
 
So what should you do instead (in idiot terms please! ;)) as I have a BMC CDA kit on mine with one of those little filters on that came with it?

Cheers, Shelton.
 
good read type_r_lover ;)

i agree with it too, cars should come with oil catch cans from factory really...
 
My cam cover breather has a cusco catch tank attatched to it with the other connection on the catch tank venting to atmosphere.

Where the breather pipe would attatch to the aem cai is blocked off.


As in the post above, any oil vapour that does get sucked into the inlet system via the cam cover breather will reduce the octane rating of the fuel you are using. Not good if you have a tuned or standard motor.

Yes you might get a very small amount of moisture build up inside the cam cover if its been wet and cold out and the car is parked in these conditions. As soon as the car is started and driven and warmed up this will soon evaporate.

Have you even tried mixing oil and water. They dont mix, oil will sit on top of water, add some heat and the water will evaporate.

Had a previous nissan that was tuned to 350hp and that stood several times a year for 3-4 weeks using the same catch tank setup. Yes it did have a build up of moisture in the head. But once run for 20 minutes all the moisture was removed and back to normal.


If you use the car everyday then there wont be any build of moisture.
 
PCV are a funny thing to get your head around. A lot has been written on them, but basically on an NA engine you should always have the line going from your intake to your crank case. The oil catch tank will catch the oil, and you won't have a problem with oil deposits in your intake. On your setup I would therefore reattach the catch tank to the intake.

I suppose your Nissan was forced induced for 350bhp, and it's a much different theory which applies then.

On an NA K20a you shouldn't use a vented line (ie through a filter), but addp an oil catch tank with a pickup in your air intake.
 
Excuse my ignorance as you have forgotten more then I know about NA tuning.......

But one thing confuses me.

"You would now induce humid air into the motor as the PCV system is supposed to be sealed"

How is the PCV system sealed as standard? I thought the breather in the rocker cover vented back into the OEM airbox, which is obviously not sealed at all.


Apologises if I'm talking out of my anus but I neither understand or believe it.:D
 
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You are right Lee, it vents into the airbox as standard which can still allow moisture into the motor.

As above im running a catch tank from the cam cover vent thats not attatched to the airbox or in my case aem cai pipe.
 
Well it seems to me (unless the whole thing is written as confusingly as the person writting it seems to be confused, yes that is confusing in itself) that the person writting it is mixing up the 2 different systems. Basically, as simply as it can be put, you have 2 lines from the head. The one everyone removes and fits a filter to which feeds into the hose between the airbox and throttle butterfly. This (other than throwing the mist everywhere) is fine as has been said this is open to the elements anyway through the airbox.

The PCV valve (ie a pressure/vacuum valve) is in the line that goes direct to the head (so when the throttle is shut the vacuum would be lost if this is not blanked off, the filter would have the same effect as it being open) but again this could (although would be even more messy) have a little filter fitted on the head end.

If anyone can come up with a valid reason why this is wrong then please enlighten me.
 
So what should you do instead (in idiot terms please! ;)) as I have a BMC CDA kit on mine with one of those little filters on that came with it?

Cheers, Shelton.


If I was you I would ditch the BMC matey. Its through this induction kit that my engine went bang!!!! So much crap gets stuck in them, take it off and give it a shake and you will see what I mean. Only giving you the heads up because my engine blew up and would hate the same to happen to you....
 
If I was you I would ditch the BMC matey. Its through this induction kit that my engine went bang!!!! So much crap gets stuck in them, take it off and give it a shake and you will see what I mean. Only giving you the heads up because my engine blew up and would hate the same to happen to you....

Glad you posted this mate, i was about to do a deal with someone off "The Other Forum" for one;)
 
If I was you I would ditch the BMC matey. Its through this induction kit that my engine went bang!!!! So much crap gets stuck in them, take it off and give it a shake and you will see what I mean. Only giving you the heads up because my engine blew up and would hate the same to happen to you....


How can a little filter make your engine go bang??

Would like to know what damage was done and how a little filter can cause this.
 
The BMC intake has a hose that can should be pointed towards the wheel arch.

Some have obviously pointed into the wheel arch.
 
How can a little filter make your engine go bang??

Would like to know what damage was done and how a little filter can cause this.

I put it in my post, it sucked up loads of crap. As i said take yours off and give it a shake, you will see what I mean.
 
Apologies for dragging up a real old post, but interested in what people thoughts are on this today, in particular with a FN2.

From what the report says, it should be a closed system (rocker cover), how true this is I don't know. But the argument that the rocker cover is vented to the air intake which is not a closed system I believe to be true. So the small filter has no affect on a pressurised system which if you agree with this argument, the closed system is not there in the first place (Am I wide off the mark here?).
From what I can read from it is, filter will allow damp in to the rocker cover when sat with engine off, but so could an open cone air filter if it's not a closed system. Admittedly further to travel. Advantages of the filter is preventing misted/oily air back into the intake system weakening the the mixture.

Is it worth doing, or is in a no no?

Cheers
Dave
 
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It's not 'worth' doing at all. It's something you end up doing after you've modified your car and lost some vac ports or returns.

A catch can, you could argue is worth doing. Not really necessary on these motors though IMO.
 
From what the report says, it should be a closed system (rocker cover), how true this is I don't know. But the argument that the rocker cover is vented to the air intake which is not a closed system I believe to be true. So the small filter has no affect on a pressurised system which if you agree with this argument, the closed system is not there in the first place (Am I wide off the mark here?).

It's not a closed system, no, but the air box/intake is a negative pressure system. This means that when the engine is running there will be a low pressure zone in that box, so there will always be suction against the rocker cover from that - hopefully greater than the pulsing pressure differential in under the rocker cover.
 
It's not 'worth' doing at all. It's something you end up doing after you've modified your car and lost some vac ports or returns.

A catch can, you could argue is worth doing. Not really necessary on these motors though IMO.

Catch cans are only ever useful on motors that have lots of blow by, like RB's and JZ's. There's absolutely no reason to have one on a standard K20. If it was boosted i'd do it.
 
Thanks for the replies and the info guys, for now I’ll leave be.
Hopefully in the next 12 months there is a possibility that I will supercharge as this is a project car for me, so will bare it in mind for then.

Cheers.
 
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