Vagitarian

Hey guys, I am making a catch can for my setup. I am stuck at how to fabricate the top though.

I have 3 lines coming from my engine to the can, drain **** at the bottom, baffling/steel wool between the inlet and vent, but I cant decide on how to vent.

I see most people use filters on top, but 3 of those is a little expensive, I dont have them, and would take up 2" more height.

Can I simply drill holes in the sealed top and "vent" to atmosphere out the top??

I assume all the oil would get trapped in my thick wool and baffling, and only air would be escaping the top. Aside from the smell, is there any downfalls to simply drilling holes?

Ash J. Williams

why do you people insist on atmosphere venting? you know, if you apply vacuum to it, your rings will thank you. route the top to the intake tube on your compressor inlet.

wantboost

iTrader: (2)

I have a catch can built by some Japanese race shop where they used a piece of metal with holes in it as the outlet, its simply a square on top. I'll post pics if I can find them

KevinEF7

I would say its fine as long as the top drilled holes arent right beside the inlet of the 3 ports, youd want the air/oil/vapour to be forced through the steel wool before being allowed to escape

Vagitarian

Well I figure holes on the top would be fine but was not sure, since the filter is essentially just letting air escape the top. I suppose there an extra filter, but I believe my thick steel wool would be enough filtering

wantboost

iTrader: (2)

Yea on this can the outlet is on the other side of the inlets... as long as you have sufficient baffling and steel wool in the can, nothing should come out of the vent... I would however put a drain back in since rye can will fill up

Ash J. Williams

i do hope your inlets go to the BOTTOM of the can.

spAdam

iTrader: (1)

Steel wool sucks and rusts and falls apart. Use this stuff:

Vagitarian

Why would the inlets be at the bottom? Then the tank would never be able to accumulate any oil?

Ash J. Williams

the inlet and outlet need to be on the opposite side of the separating media, otherwise the contaminated air will simply get sucked back in the engine and the oil and water vapour will not have time to condense and fall out.

wantboost

iTrader: (2)

The inlets on the bottom would never work.. they would just fill with oil and the can would be pointless

Ash J. Williams

give me a minute to draw up a simple sketch.

Ash J. Williams

here you go

spAdam

iTrader: (1)

I need to finish designing the check valve that I came up with. Basically a pcv valve. Has a light spring so that any pressure (2psi or whatever depending on the spring) in the can allows it to purge to the atmosphere. Plumbs to the intake tract otherwise. Best of both worlds.

Ash J. Williams

ideally, the can should only see vacuum

wantboost

iTrader: (2)

We don't run a closed system... we vent crankcase pressure to atmosphere

Ash J. Williams

i know, and i still have see no point of that. the separator media, the separator can itself doesn't do much that way.
however, even with venting, you simply vent the plug that usually connects to turbo inlet

spAdam

iTrader: (1)

Ideally.

I want to add a spare MAP sensor to the top of my can and log it one of these days, to see if it's something worth pursuing. Either way, I want something better than venting to atmosphere for sure. Used to run an exhaust scavenge setup in my old car. Worked awesome. Don't care to do it on a car with a cat though.

wantboost

iTrader: (2)

The crankcase pressure leaves the motor on its own... path of least resistance.

And as the crankcase pressure is forced through the catch can that's how the media works

Ash J. Williams

you can simply route the outlet to the turbo intake, there is plenty of vacuum there.

Ash J. Williams

sure, but at the very least follow the diagram i posted. otherwise the vapour comes in one way and leaves out of the other.

wantboost

iTrader: (2)

It comes in and leaves the outlet.... what's so hard about that?

And with plumbing it back to the turbo inlet you risk contaminating the intake charge

Ash J. Williams

nothing hard about that, it's inefficient. if you plumb it back to the turbo inlet and with proper media, you only introduce the gas vapour, which should be burned by the engine anyway.
i understand the reasoning if the car is a race car and not wanting to lower your octane rating with that, but then, you shouldn't have a cat and run the exhaust scavenging system instead.

EsotericImage

iTrader: (8)

Alot of boost set ups do not run a tube to the inlet of turbo.. Usually just a filter. So theres no place for any vacuum location. If the turbo inlet is pointing towards pass side, then theres room for an inlet tube, but most dont run one cuz the slave is right there.

Also, Alot of people do not want to let the oil vapor hit the blades.
Thus venting to atmosphere is the only option. Theres always the slash-cut option on the exhaust.. but then you have oil vapor in the exhaust.. again.. atmosphere is the other option..

As far as the rings, some evac is better then no evac. Ive seen plenty of set ups w/o any evac route..I wonder what those rings look like?


99% of the time on street cars the car is in vac anyways.. using a PCV from a turbo Supra will close when theres boost and keep it open during vac. That way you have the best of both worlds.

wantboost

iTrader: (2)

I don't run cats on anything... not even my 1 ton van that I use to tow and do track support local.

The vapors from the crankcase no matter how clean will still contaminate the intake charge and cause issues with tuning, carbon build up on intake surfaces and intake valves, and cause a false air fuel reading