Oil Catch Can on a V6 Petrol

The guys in the states are putting catch cans on their VQ40 V6 engines and catching a little oil before it goes into the plenum.
What do you guys think?
Is it worth putting a oil catch can on a petrol N/A engine?

I put one in my diesel mostly to keep the intercooler clear of the oil.
Its amazing the difference you feel once you clean you intercooler out.
If it was not for that I wouldnt bother installing it in the first place.
Why dont you just vent the PCV to atmosphere? you used to buy the little rocker cover air filters for the old holden 6s to replace the PCV would that kind of setup (maybe extended line version) work on the Navs 6?

Aussie Frontier said:

What do you guys think?
Is it worth putting a oil catch can on a petrol N/A engine?

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Yes it is.

To meet emissions laws they cant vent to atmosphere anymore.
The same principal is for petrol and diesel. crank case fumes are heavy in oil so taking that oil out of the mix before putting it back into the engine seems to make sense.Some of the web sites are saying its a harmfull mix of gases from the crankcase so best to filter that somewhat before putting it back into the plenum.
The V6 takes air in on the filter side of the throttle body and puts that inot the crankcase and then sucks it back out into the air plenum after the throttle body.
The guys in the states are pulling limkea teaspoon full for every 400 odd miles so its definately in there.
Just seems funny that the manufacturers all seem to do the same and vent the crankcase back into the plenum.
I know many guys with forced induction do it to keep oil out of the blower or turbo .

What he said ^^^ First up it is not legal to vent to atmosphere, but the arrangement of the plumbing usually means that under normal conditions, manifold vacuum draws air in through the air filter, into one port, through the crankcase and then into the inlet manifold via the PCV (Petrol engines only obviously given a deisel will not have any manifold vacuum to make a PCV work) The air drawn in though the air filter normally goes through the air flow meter so it is a metered part of the inlet air. Vent to air would mean venting both to air and disconnecting and plugging the PCV as if it is still connected it will draw in unmetered air through the atmospheric vent at the other end of the system and the idle and cruise mixtures will end up lean as a result.

A better bet on an NA petrol engine (Even forced induction) is an oil seperator on the line to the inlet plumbing. Bottom of the seperator to the rocker cover, top to the intake pipe near the air filter. Any oil that ends up in there under full load will end up drawn back into the rocker cover courtesy of the PCV applying vacuum to the system and drawing it back in.

Aussie Frontier said:

To meet emissions laws they cant vent to atmosphere anymore.
The same principal is for petrol and diesel. crank case fumes are heavy in oil so taking that oil out of the mix before putting it back into the engine seems to make sense.Some of the web sites are saying its a harmfull mix of gases from the crankcase so best to filter that somewhat before putting it back into the plenum.
The V6 takes air in on the filter side of the throttle body and puts that inot the crankcase and then sucks it back out into the air plenum after the throttle body.
The guys in the states are pulling limkea teaspoon full for every 400 odd miles so its definately in there.
Just seems funny that the manufacturers all seem to do the same and vent the crankcase back into the plenum.
I know many guys with forced induction do it to keep oil out of the blower or turbo .

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Whatever oil you can separate from the vapour going back into the combustion process the better.
PCV was only designed to not vent these gases into the atmosphere, and in no way benefit combustion in the cylinder and infact its not good.
On top of being no good for combustion the oil in the vapour can rather quickly create a crust on the inlet valves which if left unattended will reduce airflow into the cylinder greatly.

If your not pulling down your engine every 20000 or so (sometimes it takes longer to encrust), fit a catch can...it cheap insurance.



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So general thought would be a definate yes.
The engine bay is somewhat crowded so the next question would be does it matter how far the piping is. One of the guys in the states fitted his behind the left headlight but its 9ft of piping in total.
I was thinking of on the radiator support panel behind the grill on the drivers side.
Any thoughts or reccomendations on what to buy?

A container as big as possible in the coolest position is best.

Probably a minimum 10mm ID vacuum hose would do the job...just make sure it wont collapse under high vacuum.





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So in front of the radiator support panel would be a good place then as it shouldnt have any heat from the engine.
I have been looking and their appears to be quite a few to choose from.
Should I go with a fully welded unit or the type that I can get into?
Some of the boys in the US go with just a cylinder then get some really coarse stainless steel wool and fill the canister with that.
What type are the diesel guys running?

Choices so far look like
Unbaffled canister

Sealed but probably unbaffled

Fully welded and media filled supposedly


choices choices choices

I would go the top one.

I just got one for the '22 and found it has no way of opening it
so am fucking around to mod it so i can experiment with different media and configuration that work best.





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Let's not forget that the gas that is being pumped out of the crankcase - once you remove the oil vapour - is EXHAUST gas. It's crap. It should be heading out to make more holes in the ozone layer and giving one more tree-hugger an excuse to get a 'woody'.

Oh, and for the record: yes, fit a catch can. I agree!

I dont know how your engine bay is mapped out but i was able to fit mine on top of the passenger wheel arch in front of the firewall.
I dont know how to upload a photo but I got a similar one to the top it has no baffles its a square dr1ft and I checked the piping a wek after installing it and the return line was clear of oil. So without a baffle it still works effectively.

Well we should have the same engine bays Mad as we both running th same engine.

Just bought this unit of EvilBay for close on $50 delivered


Am hoping I can open it up and mod it a little with the incoming tube feeding to the bottom of the canister and then insert Stainless Steel Wool to act as a media for the oil vapour to accumulate on

The line size should be 10mm
Will try if I can to replace it all so that I have no joins etc and have rubber going to the catch can and clear on the return for a while to see if its doing as it should

Aussie Frontier said:

Well we should have the same engine bays Mad as we both running th same engine.

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Im running the oil burner model not the V6.
But I have managed to get technology tollerant and upload some pics of my install. You may be able to







There was factory holes pre threaded in that spot where i made a bracket out of stainless to suit and cut out L shaped holes so you can slide the cannister in and out easily. The last pic you can just make out the slots.

Looks like its meant to be there.
Ill have to wait till mine gets here to figure out where to mount it .
I was going to swap out the drain plug for a valve with a drain tube so i wont have to move it
However I still have to see where it will go.At this stage am thinking in behind the grill next to the right head light as my engine bay is somewaht a mess lol . Nissan bits everywhere

A good cheap mod that has merits, looks like I'll be doing this one over Easter as well, along with Raptor bed lining, and canopy refit etc etc etc etc

Yeah it fitted in the hole like a bought one.
Looks inconspicous apart from the red plumbing. the D40 uses 28mm hose or there abouts.
So I wanted to make sure the pipe was oil resistant and could cope with both pressure and vacum. @ $15 a metre its not cheap stuff.