Catch Can Crankcase Ventilation

[jp4130]

Is running two hoses from the breathers on valve covers to your catch can sufficient for crankcase ventilation? I've seen a lot of RB-26s set up this way. Is having no source of vacuum detrimental.

[Skym]

You have to understand how the PCV (Positive Crankcase Ventilation) system works.

At idle the PCV valve is open and it vents blowby gasses into intake manifold from intake camcover (also the opposite way, off the exhaust camcover), so it can be induced and burnt by engine. But when engine transistions to boost, the PCV valve closes and it vents the gasses the opposite way, into PCV piping that's connected to the exhaust cam cover, then infront of turbo's, so it can be induced and burnt by engine.

The problem is, when engine runs more boost for long periods (racetrack), some of the oil moves with the blowby gasses, so enters intake piping before turbo's, goes through turbo's, etc. This affects octane of the fuel that's injected.

The way the two hose catchcans from Japan work, is they intercept and catch the oil from the exhaust camcover to intake piping that's infront of turbo's.

On racecars, they block off PCV valve part on intake manifold with a bung and do the same on intake piping infront of turbo (or use a hardpipe without a hole for PCV piping). Then they run both camcovers via hoses to catchcan. Then they have another breather hose off the catch can, that sits just behind the engine (vents to atmosphere). Only problem with doing it this way, is your venting to atmosphere, so ECU needs to be retuned to compensate for the air being lost through this breather.

[jp4130]

I understand the purpose of a catch can. My car is setup like your race car example, except I'm running filters on the breathers instead of a catch can. However it seems that their should be, or maybe it would be benificial to have a source of vacuum for the crankcase. Maybe pull vacuum via the exhaust like old V8s.

[Skym]

Do you mean the "AIR" system in this link below, that was used on Camaro?? -

http://www.camaros.org/emissions.shtml

Just seems to be more complicated and adds weight with pump, etc. The higher boost levels, higher pressure from oilpump probably push the air out of camcovers, towards catchcan.

Some run a small K&N filter (or two of them) on catchcan instead of a breather pipe. R.I.P.S would be one tuner that does this -

http://www.ripsracing.com/images/images2/regans_r33_lge.jpg

What's interesting is the Mines R34GTR demo car, Gibson Group-A R32GTR catchcan setup, as they both have multiple catch cans in series. I'm not totally sure why you would do it that way, but there must be good reason behind it???? Maybe makes sure oil doesn't hit the racetrack???

[malibusst]

they did this as one would catch the oil, then the other would catch condensation build up....


also, if its a "loose" motor, those catch cans fill up quickly, so theres two....

[Dragon Humper]

A.I.R. stands for air injection reaction, it's an emission device that is still in use today. It injects air into the exhaust to help clean up cold start emissions by burning the rest of the fuel that may be left over in the exhaust.

I am going to use a leftover from the old days and put a bung in the exhaust just after the O2 (so it doesn't get contaminated). If you google crank case evac. you'll se what I mean. I already have a catch can. I'm just going to add vacuum to it from the exhaust rushing past the bung. Just adding a small amount of vacuum to the crankcase at full power can add a few ponies coming out the back. Not to mention it cuts down on the amount of oil that weaps out of seals and whatnot under full power. A properly placed evac bung can make 10 inches (don't know the metric) of vacuum.

For those of you in an area that has emissions testing, forget it. Placing the bung after the cat still works a bit but you'll fail the sniffer test unless you block it off before testing.

Jon.

[NismoS-tune]

I went with the nismo oil separator so I don't have to worry about emptying a catch can, using more room with a catch can or losing any oil over time. It's a nice unit though I may modify it a little with stainless lines.

[mcfly]

If you don't have a vacuum source the system wont work as it should. You need a pressure differential for it to circulate the air into then out of the can.

So to do it right you need one line going before a turbo.

Vents kind of work, but vacuum source is best.

[JD74]

I went with the nismo oil separator so I don't have to worry about emptying a catch can, using more room with a catch can or losing any oil over time. It's a nice unit though I may modify it a little with stainless lines.

Where did you pick that up if you don't mind me asking ? and what did you pay for it ?

Thanks.

[jp4130]

A.I.R. stands for air injection reaction, it's an emission device that is still in use today. It injects air into the exhaust to help clean up cold start emissions by burning the rest of the fuel that may be left over in the exhaust.

I am going to use a leftover from the old days and put a bung in the exhaust just after the O2 (so it doesn't get contaminated). If you google crank case evac. you'll se what I mean. I already have a catch can. I'm just going to add vacuum to it from the exhaust rushing past the bung. Just adding a small amount of vacuum to the crankcase at full power can add a few ponies coming out the back. Not to mention it cuts down on the amount of oil that weaps out of seals and whatnot under full power. A properly placed evac bung can make 10 inches (don't know the metric) of vacuum.

For those of you in an area that has emissions testing, forget it. Placing the bung after the cat still works a bit but you'll fail the sniffer test unless you block it off before testing.

Jon.

This sounds like the way to go. Would running the line from the pcv valve hole work well? I'm thinking of doing that as well as keeping my K&N filters on the valve cover breathers.

[NismoS-tune]

Nearly $500 with today's market I'm certain I'd have to doublecheck what I paid. Any Nismo supplier can get this item.

[Dragon Humper]

This sounds like the way to go. Would running the line from the pcv valve hole work well? I'm thinking of doing that as well as keeping my K&N filters on the valve cover breathers.

The best way to do it is to remove all vents and have the system closed. The EVAC bung should pull a little vacuum at idle as well. If you find that it only pulls vacuum at WOT then you should run the PCV as well tied into the same closed system. This way you have positive EVAC at both idle to remove leftover fumes and the big pull at WOT to remove the big nasties.

You can just plumb it directly but I have a catch can allready so I will use that as well. No catch can means you'll have more carbon splatered on your bumper.



Jon.

[jp4130]

No catch can means you'll have more carbon splatered on your bumper.

Thats fine, I already get a fair bit on my heatshield/bumper from my flamethrower, I mean exhaust.

[333]

This is what it looks like on the car, all nice and neat. It doesn't take up too much room. The bottom hose is fed back to the Turbo drain so there is no burnt oil smell.

[Bruizer]

Pretty sweet set up Nershan!! but wait! Splitfires!!1!! missfire? lol. jk