RB25DET Oil catch can

[Jason062100]

I'm confused as to how the pcv works with the oil catch cans. I thought I understood that the oil catch can connects to the two pcv valve cover fittings via two hoses and you need one more hose that connects to the fitting on the right that connects to the intake for vacuum. So how come people run setups like in this picture where they don't have that vacuum and instead go straight to the oil catch can?

[GTSBoy]

That's if you're happy to vent to atmosphere, which is stupid and illegal.

[Dil-Dog]

That in the picture is the best way that I KNOW and have experience with ..... to my knowledge there is no disadvantages to this set up and thus will provide only clean air to the engine from through the filter and there is no other source like polluted blow by gas going back through, fouling and dirtying up your turbo, throttle body, intake ports, and valves. 

PS: who cares if its illegal and realistically how much more harm is it causing to the environment venting to atmosphere while your 20 year old fire breathing  RB is running ?

@GTSBoy can you explain why this set up is "stupid" ? 

Edited October 24, 2019 by Dil-Dog

[GTSBoy]

6 hours ago, Dil-Dog said:

can you explain why this set up is "stupid"

Yup, because it is really bad for the environment. Hydrocarbon emissions are a major contributor to smog, cause respiratory problems and almost certainly have cyclic/polycyclic aromatics in them that are almost all carcinogenic.

Venting to atmosphere is the lazy way to deal with the problem. A real engineer put best efforts into everything.

And it's illegal.

[KiwiRS4T]

If your catch can is just for show that's one thing but if you have a real oil control problem such as is normally found after a sustained period at WOT which usually happens only on the track (or the dyno) then you need a better set up... preferably one that includes a breather from the crankcase (upper sump).  In this case plumbing it into the intake will help to reduce crankcase pressure. A properly baffled sufficiently large catch can should catch the oil mist produced and if it doesn't then another air/oil separator in the line will.

There is a very thorough discussion of this subject in the oil control thread (just read the last half - its a giant thread).

 

[joshuaho96]

Is the crankcase vent used because an excess of oil is pushing out of the valve cover into the PCV? The 80+ page thread is just dizzying amounts of back and forth. If the issue is just a lot of oil coming out of the PCV I would wonder if an air oil separator draining back to crankcase is a decent enough bandaid solution to avoid pulling the engine to install a proper crankcase vent. 

[GTSBoy]

1 hour ago, joshuaho96 said:

Is the crankcase vent used because an excess of oil is pushing out of the valve cover into the PCV? The 80+ page thread is just dizzying amounts of back and forth. If the issue is just a lot of oil coming out of the PCV I would wonder if an air oil separator draining back to crankcase is a decent enough bandaid solution to avoid pulling the engine to install a proper crankcase vent. 

Oil has to go down the holes in the block. Blowby gases from the crankcase are coming up. The more power any given engine is making, the more the crankcase gas flowrate increases. There comes a point where the gas flow up prevents the oil flow down. One long blast of high power can take a lot of oil from the sump and trap it in the head. (Obviously).

The answer is to provide more cross sectional area for the gases to flow out of the crankcase without competing for the path that the oil uses. Hence the crankcase vent.

That is the distillation of the "why" part of the oil control thread. The recipes for success have some variation, but they all follow broadly what Kiwi said.

Edited October 24, 2019 by GTSBoy

[joshuaho96]

6 minutes ago, GTSBoy said:

Oil has to go down the holes in the block. Blowby gases from the crankcase are coming up. The more power any given engine is making, the more the crankcase gas volume increases. There comes a point where the gas flow up prevents the oil flow down. One long blast of high power can take a lot of oil from the sump and trap it in the head. (Obviously).

The answer is to provide more cross sectional area for the gases to flow out of the crankcase without competing for the path that the oil uses. Hence the crankcase vent.

That is the distillation of the "why" part of the oil control thread. The recipes for success have some variation, but they all follow broadly what Kiwi said.

Any thoughts on the Tarmac Solutions air oil separator? Supposedly uses the dipstick as a ghetto crankcase vent.

[GTSBoy]

Don't know it. But the dipstick is about 10% of the required cross sectional area!

[KiwiRS4T]

1 hour ago, joshuaho96 said:

Is the crankcase vent used because an excess of oil is pushing out of the valve cover into the PCV? The 80+ page thread is just dizzying amounts of back and forth.

Yes its a long read but but you can get away with reading just the last third. In it many possibilities are explored and you will find that pretty much a consensus emerges. And if people are not familiar with the concepts then another, but redundant, thread of equal size could be created with people repeating points of view that have already been thoroughly canvassed.

[Dil-Dog]

Basically @Jason062100 you can look at it in 2 very simple ways....

#1 The picture you shown where the 2 PCV ports on the top go into a non-return catch can that vents to atmosphere, and the side PCV port is blocked/Capped. - This method is the absolute best and cleanest for your engine, no ifs ands or buts... its is the best.

#2 If you are a good boy and care about the law and environment, ? ... run a catch can that has a return port but AT LEAST run the return port somewhere after the turbo like on the charge piping so you at least dont foul up ur turbo with carbon build up and oily greasy gunk. 

Choose Wisely and join the dark side ?

[joshuaho96]

My view on emissions is that CO2 is a way bigger problem that one lone individual cannot really solve. You can avoid using plastic bags, straws, buying endless piles of trash that you never use, drive an EV, etc... but it doesn't even come close to helping the problem, not when the rainforest is being slashed and burned in south america for agriculture. They use the land for a few growing seasons then it's on to the next plot to slash and burn.

But stuff like unburned oil spraying out your atmo vent catch can or exhaust PCV system is getting into your water, it's getting into the roadways and causes extremely slick surfaces when it rains

[KiwiRS4T]

9 hours ago, Dil-Dog said:

Basically @Jason062100 you can look at it in 2 very simple ways....

Life is simple when you 're a simpleton. Ignorance is bliss. Be happy.

[Ben C34]

9 hours ago, Dil-Dog said:

but AT LEAST run the return port somewhere after the turbo like on the charge piping so you at least dont foul up ur turbo with carbon build up and oily greasy gunk. 

Well that just won't work. There's a reason they vent to in front of the turbo. Also turbo won't "foul up"

[admS15]

What's a cat can?

[GTSBoy]

I'm seeing some very wilful ignorance playing out here.

Not one mention of boost flowing backwards through the catch can from the wonderful advised method of connecting it up after the turbo.

Beauty may only be skin deep, but stupid, well that goes all the way down to the bone.

[GTSBoy]

Oh, AND REMEMBER TO VOTE REPUBLICAN!

[Dil-Dog]

Oh shit yes i stand corrected the veterans definatly have a point the the return must go infront the turbo and not on the charge pipe... my bad. Never ran one with a return so I dont have any expirence with it. Ignore my previous comments. Yall dont gotta be fags all the time by the way... next time try help and educate a noob out