Catch can flow discussion

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iamdub

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I installed this cheap amazon chicom catch can 5 yrs ago. I added pot scrubber matl and drain valve. Its still working good today.
View attachment 412499
View attachment 412500


That's the one I installed on my brother's truck and two or three others. It's basically the same as what I just bought for my friend's Tahoe, the difference being this one has a 750ml reservoir. I've added the stainless scouring pad to mine and all of 'em I've installed.
 
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iamdub

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My thoughts is that gravity helps the oil drop out of suspension once the air has entered a larger space and changes direction. Baffles help by making the air change direction, like in a muffler, and causing the oil to stick to the baffle. Also in the same line of thinking with gas lines in your home and how they have a down leg on verticle runs for any debris that may get into the line to drop out.

Gravity might play a small role in it. But, it's atomized oil droplets riding an air current. They ride it out of the crank case, through the valve cover (as well as additional droplets from there), through a hose, etc. What's to stop them from riding that air current straight from the port dumping into the reservoir across to the outlet port? So, the coalescing media is required. I think if the air hits it first, the droplets collect and are then too heavy to make it from where the port dumps into the reservoir, across and out. If it goes through the void of the reservoir then hits the media, yes, it's stalled and the droplets will eventually be too large for the air currents (vacuum, actually) to hold them to/in the media and then gravity is able to overcome so the now larger drops fall. But, there's still a suction on the filter media and surely some oil is bound to be pulled through and up the hose leading into the intake manifold.


I always thought our Catchcans.com one should have the input on the side port and exit through the top port. One of the reasons is that if oil in the can gets full enough up close to that side port that is sucking to the intake, any bumps or jostle of the can could easily let oil splash up to that port and suck oil in. Also, usually the suction port on any of these cans I've looked at are usually at the top and/or have a filter or screen before it. Thinking to keep oil from getting to it and sucked into the intake.

Valid. But, this is why you get a large reservoir if your engine passes that much oil or check/drain your can more often. But, hey, if it's catching that much oil, then it's gotta be working that good, right? Or your engine has problems. lol


The cheap ebay can I had on previously for 4 years had both ports on the side, one about an inch below the other. The bottom port was the in and top port was out.

The arrangement makes sense. But I'm a firm believer in scrubbing media.


I have a breather type can on the blown mustang, but also run a mechanical vacuum pump. The discharge from the pump goes into the side of the can. Inside the can between the side port and the top opening are 2 or 3 staggered metal tabs that are the baffles and a small air filter is at the top. It does not return to the intake. The air hits a baffle plate and turns 90* to get around it. Oil catches on the plate and drops down into the can.

A breather filter sure would make things easy, but also smelly.


When I first installed the catchcans.com one like yours last year I hooked it up with side port in/top port out. Worked fine. After talking to you and also sending an email to catchcans.com asking correct orientation, both telling me top in, side out, I switched it. Works fine also, lol.

This is my conundrum! I see how it'd work fine with the flow in either direction. I just think it's optimal going the way they suggest. The confusion was when I noticed the Amazon/ebay cans all have theirs reversed. I've never paid attention to it until now. Clearly, they work fine like this. I change the oil on my brother's truck and, after 4+ years, his intake manifold is dry. It's a healthy Gen3, so it moves very little oil to begin with. The expensive can companies don't advertise such details that I could find.
 
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iamdub

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I have a $130 Mike Norris Motorsports catch can on my C5 Corvette. Inlet on top, outlet on side. It doesn't catch liquid any better than the $30 side inlet and outlet chicom cc that's been on the Yukon for 5 yrs.
View attachment 412525


That's a catchcans.com one. They're one of the pioneers for these things. I bought mine in a group purchase (on ls1tech, I think) back in 2011ish- back when there weren't many companies offering them and especially no dirt cheap ones on ebay or Amazon. Years later, I exclusively buy the Amazon ones since, just as you said- they function just the same but at a fraction of the price. What you're paying for with the expensive ones is appearance and usually vehicle-specific bracketry and hoses. I have tools and metal stock to make my own brackets and regular hose clamps (spring, worm, EFI, etc.) suit me just fine.
 
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iamdub

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My thinking on those models with the round brass filter covering the port, that port should be the exit back to the intake. If it was the input from the valve cover the oil will catch on that brass filter on the input side of it. Will it get sucked/seep through to the can side of the filter, yes eventually but may cause a restriction to the air going into the can

Wouldn't it work better then? If the oil has been stalled and scrubbed from the air, and has coalesced on/in the filter media (the bronze plus the added scouring pad), the droplets would already be too big to remain "in flight" to get to the "unprotected" outlet port. Going the other way, the oil is already stuck to the filter media and is being pulled through via engine vacuum at all times. Eventually, it'll get through and make its way up the hose to the intake manifold.

The oil would have to pretty much be solidified in the hose to be a restriction. Obviously, it's very far from being a solid. Also, a restriction stalls air flow and this weakens the vacuum on a fluid substance. If there's enough oil going through the PCV system (through that tiny hole in the PCV "valve", for one), to fill the 5/16" hose, then your engine was already moving that much oil and it needs more help than a catch can would ever provide. Does an oil-soaked brass filter reduce air flow? Of course. But it's not enough to cause excess pressure inside the engine or affect engine vacuum in any amount the PCM sees and reacts to.
 
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I have the JLT 3.0 oil catch can installed on my 07 Yukon XL Denali, and here is an excerpt from their web site:

"A filter on the inlet side of the oil catch can traps fine oil vapors and releases them once heavy enough to fall. By the time the oil gets through the filter it's too heavy to be passed on into the intake.

The tank holds 3 oz of fluid, while that may not sound like a lot, you shouldn’t see that much oil in your PCV system. Drain it every 2000-2500 miles on most applications and you will never come close to filling it. Average collection for most applications is roughly an ounce every 1000 miles."

You can see the inside of this catch can with an explanation of its function in the following YouTube video as the 2:45 minute mark:


View attachment 412545


Yes! This is my exact train of thought. Although, unless I missed something, the guy in the video has his connected opposite of what JLT says.
 
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iamdub

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I swear the video says opposite what the text you quoted says. I think they mean the inlet port of the can not the intake of the engine. According to this the guy in the vid has it backwards.

Okay, so I'm not just tired and misunderstanding.
 
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The arrangement makes sense. But I'm a firm believer in scrubbing media.




A breather filter sure would make things easy, but also smelly.
The old cheap can did have a screen seperating the upper and lower part of the can and the corresponding ports.

As far as the open breather, yeah a bit smelly but it's not a daily driver, has a large cam, longtubes and no cats so it smells anyway
 
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The old cheap can did have a screen seperating the upper and lower part of the can and the corresponding ports.

Ah. That's better than it just relying on gravity and [rather ineffective] fluid dynamics.


As far as the open breather, yeah a bit smelly but it's not a daily driver, has a large cam, longtubes and no cats so it smells anyway

Right. Perfectly fine for a race car. But could be an annoyance on a family hauler kept in the garage. I don't have cats on mine. That, coupled with jacked-up idle spark tables leading to more raw fuel in the exhaust makes mine a nuisance if idled in the garage. Other than that, I appreciate just smelling hot metal and plastic when I pop the hood after a drive. If I ever smell anything, then I'll know right away I have a leak.
 

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