Oil catch can

[h4X6]

OK sorry for the stupid thread.

But oil catch cans... I cannot wrap my head around them.

So I run both blow bys off the valve covers into the can. Do I need a third hose coming out of the can vented to the air? Or just the two hoses that go to the valve covers? And that's it...

Sorry again for the dumb thread.

Sent from my Galaxy Nexus using Tapatalk 2

[Skym]

PCV system is simple on a Skyline. When at idle, PCV valve is open on intake plenum and blowby gas goes into intake plenum from intake camcover breather fitting, vacuum hose and into intake infront of turbo via exhaust camcover fitting, vacuum hose, hardpiping. Once engine transistions to boost, the boost pressure inside intake plenum closes PCV valve and blowby gas from both camcovers (why fittings on both camcovers are joined together by a vacuum hose) exit via exhaust camcover and goes into intake infront of turbo and into engine where it gets burnt by engine.

The problem is too much oil gets to head at higher rpm, so oil starts to exit exhaust camcover with the blowby gas. This is where a catchcan is fitted to separate the oil from the blowby gas and only let the blowby gas enter intake infront of turbo. Oil in blowby gas supposedly can drop octane of fuel inside cylinders hence cause engine to knock and blowby gas cause a dirty burn inside cylinders (cleaner burn = more hp).

On turbocharged racecar engines that are at higher rpm, high boost levels most of the time, they remove PCV valve, block hole where PCV valve was and block hole infront of turbo and run both camcovers to catchcan via vacuum hoses. Then run a breather / vacuum hose from catchcan to just behind engine which vents blowby gasses to atmosphere (cleaner burn inside cylinders). On a road car due to emissions it has to be put back into intake.

[cory]

Good explaination

[h4X6]

thanks for the explanation that helped with me understanding how the system works

but lol which do i need? a catch can with 2 ins and a vent to atmosphere? or just the 2 ins and no vent?

[Skym]

The way it's configured depends on use of car, street, racetrack, etc and if it has to pass emissions testing.

Usually with street car (emissions), 1 litre Japanese tuner (Cusco, etc) or aftermarket (D1spec, etc) made catchcans (2x fittings on catchcan), you put a catchcan inbetween exhaust camcover breather and hardpipe that goes to rubber intake pipe infront of turbo. The catchtank catches the oil that exit's camcovers at higher rpm, boost levels and vents into hardpipe that goes to rubber intake pipe infront of turbo when car is used on street, motorway, etc.

The two vacuum hoses to catchcan from both camcover breathers and vent to atmosphere near bottom of back of engine from catchcan via vacuum hose should only be used on a racecar or engine that doesn't idle alot. If engine idles alot in traffic you need the PCV valve and the street setup.

From what I understand, the size of catchcan is sized to half sump capacity (2 litre), but motorsport rules say it's matched to I think was engine capacity (would need to consult a racecar engineer or contact local motorsport authority to find out what size catchcan suits engine). I think it was at least (minimum) a 2 litre catchcan is needed for competition use and can get away with 1 litre on the street (actually I think some are 800cc catchcans).

[h4X6]

OK so I want to make sure I understand this

I'm running a street car that needs emissions. So if I run both intake and exhaust hoses to catch can with no vent to before Turbo I should be OK? Especially with emissions?

I currently have the vent to the turbo as its a vg30 Turbo but I have a gt35 being installed soon so I would like to get rid of the vent to before the Turbo.

My plan would be with gt35 Turbo installed. Blowbys to the catch can with no vent at all... is that possible?

Sent from my Galaxy Nexus using Tapatalk 2

[Skym]

No.....Not venting blowby gas can result in too much pressure inside engine and the pressure finds the weakest point to exit (failed turbo seals, camcover seals, etc).

I would run street setup as mentioned above. Also if you do vent to atmosphere from catchcan, I was warned that it can affect ECU tune, so that would need to be adjusted to suit.

Here's the street setup on street spec JUN built R34GTR with big single turbo at 1:39+ -

http://www.youtube.com/watch?v=tbSmCf2j1mw

[h4X6]

OK so run the two lines to the can and then have a third hose or port to vent to atmosphere or back into before turbo. Got it now. Thx

Sent from my Galaxy Nexus using Tapatalk 2

[knate]

No no no run one line from your exhaust cam cover to catch can, run other line from catch to your intake before the turbo. If you you run a line from each of your cam covers you need a third line to your intake before turbo. Or instead of running a line to intake before turbo you need to have a filter that is open to atmosphere

lol skym got it explain before i finished typing

[Skym]

No.......Filter on catchcan is not the best way, as you need a vacuum source to draw blowby gas out of engine. Air running under car is the vacuum source on a racecar, hence why vacuum hose from catchcan exits just behind engine. On street car the engine becomes the vacuum source at low (car is not moving in stop, start traffic), high rpm.

On a dry sump setup the multistage pump itself becomes the vacuum source (best way to permantly solve blowby, oil starvation problems on RB engine) and I think has a vent type of catchcan with filter in the system (only time I think the filter type catchcan setup should be used) to vent the blowby gasses to atmosphere.

Also another way is into exhaust with a one way valve plumbed into vent hose.

[h4X6]

OK Lets see lol

Leave the one hose going from intake side to the intake then one hose from the intake side to the catch can.

Exhaust side do a hose to the catch can.

Then from catch can a hose to before the Turbo.

Sent from my Galaxy Nexus using Tapatalk 2

[beacher1B0]

Essential : Exhaust cover -> Catch can -> Intake before turbo but after Air Flow Meter

Max Protection : As above and Intake Cover -> 2nd Catch Can -> PCV Valve(Intake Manifold)

Constantly monitor how much oil has accumulated in catch can, and ensure you have no leaks in your setup.

[Skym]

Only need catchcan on exhaust side, as PCV valve on intake manifold closes when engine is under boost. Oil only exit camcovers when there's alot of oil, blowby in head at higher rpm, higher boost levels. Also blowby (air, exhaust gas, etc passing rings that goes into sump, through oilpump, through oil galleries and ends up inside camcovers) is at it's worst when under high boost level, higher rpm.

Exhaust camcover breather > vacuum hose (supplied with catchcan) > catchcan breather fitting > blowby, oil gets separated by catchcan > other catchcan breather fitting > vacuum hose (supplied with catchcan) > factory PCV hardpiping > rubber pipe infront of turbo.

Also I think on JUN R34GTR they blocked exhaust side exit on breather fitting and made it exit on intake side of engine to catchcan, then from catchcan into intake pipe infront of turbo.

[h4X6]

ok got it! thanks for all the help and clarification