Catch can - drain to sump.

[FATGTS-R]

Hi guys,

I have heard of catch cans where the oil that is collected is then drained to the sump somehow instead of just emptying the can or running it back to intake.

How is this style of catch can set up? I am sure its not as easy as just plumbing a line into the sump from the can otherwise nobody would bother with the cans and just run hose from the rockers straight to sump.....right?

[Col-GTSX]

Well draining to the sump could be a bad thing...

The crank case preasure is different to the cyl head preasure.

If you were to run a connection inbetween the crankcase and head you would even out the pressure. This would make the crank case preasure build and put extra pressure on the back of the pistons. So the motor would labour to return the pistons to the bottom of their stroke.

All catch cans are setup just to ventilate the cam case pressure. It takes ages to fill the 800ml catch cans. Not allot of oil makes it there. Its more about a remote area to ventilate the pressure. As a standard PCV does not flow enough of this pressure....

Cheers Col

[2LV8ETR]

The way I have mine set up is with a mini ball valve hanging off the drain point at the bottom of the catch can. After the ball valve I ran a silicon hose that I tapped into the sump. I welded a plate to the inside of the sump and that's what I tapped into.

The only reason I have done this is because the engine was out anyway and I thought, "why not?"

Normally when you do an oil change you'd just drain the can by undoing the clamp then pull the bung out of the end of the drain hose, allowing it to collect into a container of course. Now all I do is open the 1/4 turn ball valve and let the oil drain into the sump - Magic!!

If you want to give it a go I highly recommend that you don't tap into the sump without reinforcing it first!

[Col-GTSX]

2LV8ETR very very good idea...

There you go. If you really want to drain to the sump then do something like this.

Although only open this valve when the motor is shut down. The only other thing is the oil in the catch can will be cold, so flow will be slow. You will not be able to get it all out as cold oil is thick oil... especially when its used cold oil....

[2LV8ETR]

2LV8ETR very very good idea...

There you go. If you really want to drain to the sump then do something like this.

Although only open this valve when the motor is shut down. The only other thing is the oil in the catch can will be cold, so flow will be slow. You will not be able to get it all out as cold oil is thick oil... especially when its used cold oil....

I got the idea of Sydneykid if I remember correctly, kudos to him from me too.

Leaving the valve open overnight with a hose pulled (quick clamps - no real pressure in the PCV system) lets it drain nicely. But I always leave a post-it note on the facia as it reminds me to close the valve before starting the engine.

[FATGTS-R]

I like your idea 2LV. Sounds simple enough.

But I was hoping there was a "automated" way of doing it but thinking about it Im not sure there is.

[2LV8ETR]

I like your idea 2LV. Sounds simple enough.

But I was hoping there was a "automated" way of doing it but thinking about it Im not sure there is.

Yep, there is - you lazy bastard! :headspin:

Instead of using the ball valve, use a electric or pneumatic valve.

For the electric system, select a valve that closes when a voltage signal is sensed and connect this to the ignition system. When the car starts, the valve is triggered by the voltage from the ignition and closes the drain to the sump. When the engine stops, the valve opens and drains the oil to the sump.

For the pneumatic system, select a valve that closes when a positive pressure signal is sensed and connect this to the PCV system. When the car starts, the valve senses the pressure increase in the PCV sytem and closes the drain to the sump. When the engine stops, the valve opens and drains the oil to the sump.

The impossible is managed immediately, miracles take a little longer my friend! Give it a go!

[awurth]

On my Wifes old SR20 there is a drain at the back of the turbo side of the motor and when you put a front mount on and change to piping you just get a small vented catch can to sit on the fire wall with the head venting to the top it and run a pipe from the bottom of the catch can back to the drain on the motor, why use a valve to stop the oil flowing back? Thats the sort of setup I would use, if you wanted to you could use the turbo drain to tap into to let any oil drain into the sump.

[2LV8ETR]

just get a small vented catch can to sit on the fire wall with the head venting to the top it and run a pipe from the bottom of the catch can back to the drain on the motor, why use a valve to stop the oil flowing back?

1: Vented catch cans are illegal - over here at least.

2: Vented catch cans vent to the atmosphere thus fouling your engine bay with oil vapour deposits (even with the piddly filter).

3: If there was no valve to stop the pressure returning to the can then your crankcase will ventilate into the bottom of the can. The PCV system works on a one way route and you've just created an interruption.

[Col-GTSX]

2LV is right... A direct connection between the crank case and catch can would be a stupid idea. Oil vapor under you bonnet is not onlt illegal but its pretty stupid. I have seen many engine fires where the filter catchs on fire due to a little spark....

You ever seen a 4wd on fire. Usually its because they use a coke bottle and a piece of garden hose to ventilate the front diff... Thats why compaines like TJM make a non ventilated system which complies with the CAM's and all states...

Dont do it the dodgy way, do it properly.

A ball valve cannot fail, an electrical setup is prone to fail (im an auto elec, id know). What happens if the electronic valve fails, opens due to bad connection. Crank case spews oil back to the catch can. Catch can over fills and blows a hose or oil comes out the filter. Oil on a hot exhaust or turbo. Guess what "FIRE".... You need to make it safe, so think about 2LV's idea (or sydney kids) its been throught out properly.

I could make an elecronic system but i wouldnt trust it. So ball valve is the way to go i reckon.

[raist60]

lol ive blown oil all over hot exhausts before, all it does is SMOKEEE!!! it was very impressive.

besides if you've got enough pressure to push your sump oil up the drain tube you got more to worry about than a fire. theres nothing wrong with running a line back into your sump if you have a vented can. As for the vent, just run a hose down and point it at the ground.

[2LV8ETR]

lol ive blown oil all over hot exhausts before, all it does is SMOKEEE!!! it was very impressive.

besides if you've got enough pressure to push your sump oil up the drain tube you got more to worry about than a fire. theres nothing wrong with running a line back into your sump if you have a vented can. As for the vent, just run a hose down and point it at the ground.

Have you ever seen a doorslammer running the 1/4, throwing a piston, cracking the block, spilling oil onto the hot exhaust (which is glowing white) and causing flames to piss out everywhere?

Remember the dude at the Jamboree who blew his clutch on the line? The clutch caused an oil fire that trashed his beast.

Last year in the WRC series a car retired due to an oil fire from a seperated turbo oil line spilling onto the exhaust housing.

EGT's run about 150°C at idle to 760+°C under an extreme load. Normal running temps will be between 260° to 480°C. The flashpoint of your typical motor oil is 200°C. You can work out the math. The risk of an oil fire in a motor vehicle is low, but you'd have to be rich to want to risk it.

As for venting to the atmo - The Colonel said it best:

Dont do it the dodgy way, do it properly.

[Col-GTSX]

The colonel????

Me dont understand...

So so so so so funny i read it now. This afternoon a WRX came into work for a re-wire after an engine fire due to a oil catch can...... LOL whats the chances that i might be right....

2LV.... Maby we were correct in saying its dangerous.... LOL

Just so funny i see what i was describing come into work like an hour after i state it.... LOL

If you dont agree then ill have them write it down on paper and ill mail it to you. As the owner knew what had happened and he said he was told to fix it only 2 weeks ago by his mechanic.... So funny, people dont listern...

[mjfawke]

Well draining to the sump could be a bad thing...

The crank case preasure is different to the cyl head preasure.

If you were to run a connection inbetween the crankcase and head you would even out the pressure. This would make the crank case preasure build and put extra pressure on the back of the pistons. So the motor would labour to return the pistons to the bottom of their stroke.

All catch cans are setup just to ventilate the cam case pressure. It takes ages to fill the 800ml catch cans. Not allot of oil makes it there. Its more about a remote area to ventilate the pressure. As a standard PCV does not flow enough of this pressure....

Cheers Col

For a start, the head(s) and crankcase are connected, otherwise the oil cannot return. On the RB engines, there isn't a vent in the block, only the rocker covers are vented. Under high vacuum conditions, air is drawn through the PCV valve into the inlet manifold, but under all other conditions, the valve is shut. Under boost, blowby is vented into the air intake in front of the turbo.

The whole point of a "catch can" system (for road use) is to separate the oil vapour out of the blowby gasses, so that oil is not fed into the inlet. There is nothing wrong with a catch can draining to the sump, as long as it is (a) efficient at getting the oil out and (B) the blowby gasses are fed back into the turbo inlet.

For motorsport, the catch can is to catch the oil from the engine when it lets loose - usually there is so much blowby when a piston goes that most of the oil is blown out of the motor through the vents.

[Col-GTSX]

Yes the crank case is connected to the head.... Obdivouslly.... (check my spelling)

But yeah... There are a few ways to look at it...

As for a simple explination.... Atmospheric ventilation from a catch can is illegal.... Full stop.

The reason why is it is dangerous and is un-healthy.

I run a catch can, but dont have it vented and dont have it drainable. As it would take 2 years to fill it, i see no point is draining it even monthly. I just rip it out when i do an oil change. The catch can should be conected to the intake for the turbo. A little oil spray is good for the turbo.

Im not going to argue the pros and cons. I have seen fire after fire when it comes to mis-installation on oil cans. Please read all of the above is you are considering fitment of an oil can. I dont suggest doing it if your goona do it wrong.

Thanks Col

[Col-GTSX]

Before someone pick at it. Oil is not good for a turbo ( i mean dont pour oil down your inlet. Im just saying it does not hurt the turbo to have a little (tiny) bit of spray. Also you do not "need" to connect it to the intake, its just suggested.

Point i was trying to mark is dont make it atmospheric venting....

[awurth]

A little oil spray is good for the turbo.

It's also good for some detonation when your on load. That's my main reason for having it vent to atmosphere. Same with my GTR although it sits on the drivers side of the motor both the cam covers venting to the can and the PCV valve has been removed and the hole has a bung in it. but it doesn't drain into the sump. I don't think anything I've done is dodgey, maybe simple, all your ideas are very good and well thought out, mine might be "illegal" but if you have oil over all your engine bay from your can venting something is wrong. my filter still looks clean.