Oil Catch Cans - Another Side To The Saga

[ht_addict]

It needs to be more exact then maybe and sometimes for engineers to reliably implement something. There's just too much variability and indifferent/clueless car owners, and sometimes equally clueless service departments, to make catch cans viable widescale.

Add to all this, EVs are coming and there's zero chance catch cans will ever be mainstream between now and then.

Again, this isn't about whether me or you should do it. I'm answering the first post and subsequent posts about why it has not been incorporated into existing engine designs. We don't need to have a back and forth unless you think that it can/should be, in which case see my recent replies.

Only reason these would never become mainstream is cost, not some clueless car owners. With sales of 2.8-3.15M vehicles, that would be a huge hit to the bottom line.

 

[Anunakie]

Lots of opinions here but so far I haven't seen anyone mention my main concern about adding an oil catch can to my Stinger. As far as I've been able to gather from looking around on the innterwebs (I must say I am by no means an expert when it comes to cars lol) is that an oil catch can can increase crank case pressure. If this is indeed the case then wouldn't/couldn't that cause more problems then it solves?

 

[AusStinger]

Lots of opinions here but so far I haven't seen anyone mention my main concern about adding an oil catch can to my Stinger. As far as I've been able to gather from looking around on the innterwebs (I must say I am by no means an expert when it comes to cars lol) is that an oil catch can can increase crank case pressure. If this is indeed the case then wouldn't/couldn't that cause more problems then it solves?

How on earth could a well built, sealed system catch can 'increase crank case pressure' ?

A good catch can will reduce the amount of oil that makes it's way back into you inlet air stream.
Oil that gets into your intake air stream becomes carbon on the back ( and combustion face ) of your inlet vales ( and to some extent the exhaust valves ).
Carbon build-up on valves reduces airflow and volumetric efficiency AND increases the temperature of the valves themselves.
Increased valve temperatures reduce the life of the valve guide oil seals and increase the chances of pre-ignition.
Chemical cleaning of carbon can help ( dry ice blasting is better ) but prevention is ALWAYS better than treatment.

If you're still not convinced, don't install one, drive around for 5 years and find out what happens

 

[G-523298]

How on earth could a well built, sealed system catch can 'increase crank case pressure' ?

A good catch can will reduce the amount of oil that makes it's way back into you inlet air stream.
Oil that gets into your intake air stream becomes carbon on the back ( and combustion face ) of your inlet vales ( and to some extent the exhaust valves ).
Carbon build-up on valves reduces airflow and volumetric efficiency AND increases the temperature of the valves themselves.
Increased valve temperatures reduce the life of the valve guide oil seals and increase the chances of pre-ignition.
Chemical cleaning of carbon can help ( dry ice blasting is better ) but prevention is ALWAYS better than treatment.

If you're still not convinced, don't install one, drive around for 5 years and find out what happens

Oil catch cans build up crankcase pressure by restricting airflow that's leaving the engine. Here is a video explaining it.

 

[Anunakie]

How on earth could a well built, sealed system catch can 'increase crank case pressure' ?

A good catch can will reduce the amount of oil that makes it's way back into you inlet air stream.
Oil that gets into your intake air stream becomes carbon on the back ( and combustion face ) of your inlet vales ( and to some extent the exhaust valves ).
Carbon build-up on valves reduces airflow and volumetric efficiency AND increases the temperature of the valves themselves.
Increased valve temperatures reduce the life of the valve guide oil seals and increase the chances of pre-ignition.
Chemical cleaning of carbon can help ( dry ice blasting is better ) but prevention is ALWAYS better than treatment.

If you're still not convinced, don't install one, drive around for 5 years and find out what happens

How? By restricting airflow leaving the engine. Here is a video explaining it.

 

[oddball]

Fun fact: if you never change your oil filter then it clogs and becomes a restriction limiting oil flow and causing your engine to DIE. Therefore you should never run an oil filter!

Maybe you're getting hung up on terminology? "catch can" is a generic term, like "car", and doesn't refer to a specific design. Sometimes there's a more specific label, like "oil mist separator" and whatnot, but we're talking about aftermarket performance marketing. The manufacturers will say whatever they damn well please, so you have to look at the product yourself to see what it actually does and how well it might do it. Some "catch cans" are just beer cans with hoses. Some are very complex and very efficient. Most are somewhere in the middle.

I tried to watch that video but I don't think he ever said that you shouldn't run a catch can. He's trying to *sell* catch cans. He even says the plain ones with no media won't cause problems but won't be as helpful.

Are you worried about the can getting clogged? There's a kernel of truth in there, somewhere, maybe, but it's not actually applicable to the situation. The volume of airflow is very -very- low. Something like a slight breeze. So the can doesn't need to be very interesting to be able to flow that amount of air and help catch oil mist. Like anything else, as long as you actually do maintenance and keep things clean, it'll work just fine. Also, crankcase ventilation is operated by intake vacuum, so the pressure differential is what moves the air through the crankcase.

As for WOT, the first topic is just how long, exactly, do you keep the engine at WOT? Regardless, this is when crank vapors push back out the ""clean"" side of the system, which is why several vendors recommend or specifically design a dual-can system for those scenarios. I ran one for a while, never got a single drop, so removed it. YMMV. Something would have to to terribly, horribly, wildly wrong for pressure to actually build in the crankcase. Even if it did, it would quickly find a way out, because the design of the crankcase does not attempt to hold in pressure at all.

If you're building a true high performance engine then you don't use a catch can - you run an evacuation system that actually pulls a slight vacuum (just a few inches of mercury) on the crankcase at all times. That's been shown to give just a few more HP, the theory being it helps ring seal. But those just dump the mist overboard, usually passing through a rag zip-tied around the outlet.

 

[oddball]

Man, this one keeps bugging me. Another factoid: just putting a hose in the side of the tube does not create a venturi. If it did, then manifold vaccum ports on a carb would never work - they would always show a vacuum. It takes some actual design work to use the venturi effect, so there's no guarantee - and I find it quite unlikely - that the intake tube would "pull" vapors.

 

[Anunakie]

Fun fact: if you never change your oil filter then it clogs and becomes a restriction limiting oil flow and causing your engine to DIE. Therefore you should never run an oil filter!

Maybe you're getting hung up on terminology? "catch can" is a generic term, like "car", and doesn't refer to a specific design. Sometimes there's a more specific label, like "oil mist separator" and whatnot, but we're talking about aftermarket performance marketing. The manufacturers will say whatever they damn well please, so you have to look at the product yourself to see what it actually does and how well it might do it. Some "catch cans" are just beer cans with hoses. Some are very complex and very efficient. Most are somewhere in the middle.

I tried to watch that video but I don't think he ever said that you shouldn't run a catch can. He's trying to *sell* catch cans. He even says the plain ones with no media won't cause problems but won't be as helpful.

Are you worried about the can getting clogged? There's a kernel of truth in there, somewhere, maybe, but it's not actually applicable to the situation. The volume of airflow is very -very- low. Something like a slight breeze. So the can doesn't need to be very interesting to be able to flow that amount of air and help catch oil mist. Like anything else, as long as you actually do maintenance and keep things clean, it'll work just fine. Also, crankcase ventilation is operated by intake vacuum, so the pressure differential is what moves the air through the crankcase.

As for WOT, the first topic is just how long, exactly, do you keep the engine at WOT? Regardless, this is when crank vapors push back out the ""clean"" side of the system, which is why several vendors recommend or specifically design a dual-can system for those scenarios. I ran one for a while, never got a single drop, so removed it. YMMV. Something would have to to terribly, horribly, wildly wrong for pressure to actually build in the crankcase. Even if it did, it would quickly find a way out, because the design of the crankcase does not attempt to hold in pressure at all.

If you're building a true high performance engine then you don't use a catch can - you run an evacuation system that actually pulls a slight vacuum (just a few inches of mercury) on the crankcase at all times. That's been shown to give just a few more HP, the theory being it helps ring seal. But those just dump the mist overboard, usually passing through a rag zip-tied around the outlet.

Thanks for the response. Here Is a video of a couple different catch cans increasing pressure in the crankcase. What im trying to figure out is if this is a non issue for a stinger and if so there is any evidence to back that up. If I cant fide the info im looking for all like end up installing one and doing some testing my self.

 

[Kazz]

You can try. But you won't pry my Mishimoto catch can from my cold, dead hands. No need for upper valve cleaning at all. Just remember to empty the can regularly.

 

[oddball]

Thanks for the response. Here Is a video of a couple different catch cans increasing pressure in the crankcase. What im trying to figure out is if this is a non issue for a stinger and if so there is any evidence to back that up. If I cant fide the info im looking for all like end up installing one and doing some testing my self.

Do you know what a mbar is?
I'm not finding quick info on the noise floor of a typical MAP sensor, but it'll also very much depend on what sensor, precisely, he used. The dude is waaaaay down in the noise. It's easy to collect data. It's hard to know if the data is actually any good. The arduino saw something, but is that something any good?

Anyway, 2 or 3 mbar is not much. That's *one tenth* of the smallest unit of pressure typically logged by an ECU.

 

[LordKOTL]

...

Are you worried about the can getting clogged? There's a kernel of truth in there, somewhere, maybe, but it's not actually applicable to the situation. The volume of airflow is very -very- low. Something like a slight breeze. So the can doesn't need to be very interesting to be able to flow that amount of air and help catch oil mist. Like anything else, as long as you actually do maintenance and keep things clean, it'll work just fine. Also, crankcase ventilation is operated by intake vacuum, so the pressure differential is what moves the air through the crankcase.

...

That is what I am lead to believe about the scenario for catch cans.

When the engine is normally operating the intake is operating in a partial vacuum state and sucking in air. Crankcase vapors and blow-by are sucked through the PCV system through the intake via the intake vacuum, past the intake valves, and combusted. With port fuel injection the fuel cleans the valves. GDI doesn't spray fuel on the valves, so deposits can happen if any liquid/vapor falls out of suspension and lands on the valves.

In other vacuum pump systems, like say a vacuum brake bleeder, you always put a can in between the actual pump intake and whatever you want to apply vacuum to--in this example a brake bleeder nipple. Any liquid that is being sucked will fall into the can before it goes into the pump inlet (assuming of course the pump inlet port on the can is at or near the top of the can). If my 10th grade physics hasn't failed me, the can acts as an expansion chamber and allows heavier fluids than air or other gasses to slow down and settle out via gravity, while not affecting the vacuum pressure (or at least no more than a negligible pressure difference). That can on the brake bleeder pump serves to protect the pump from ingesting liquids which might ruin the pump. Ditto on other vacuum pumps.

A catch can operates on the same principle. As intake vacuum sucks everything out of the crankcase, the catch can acts as that expansion chamber, causing vapors, mists, and other stray liquids to fall out of suspension and into the bottom of the catch can as the speed of the fluids through the catch can drop (even though the vacuum pressure remains constant). All you have to do is clean the can regularly so it doesn't fill up (every oil chance suffices on mine), or get an automatic-emptying one. They might not be 100% perfect, but they do work.

 

[Striker's Stinger]

That is what I am lead to believe about the scenario for catch cans.

When the engine is normally operating the intake is operating in a partial vacuum state and sucking in air. Crankcase vapors and blow-by are sucked through the PCV system through the intake via the intake vacuum, past the intake valves, and combusted. With port fuel injection the fuel cleans the valves. GDI doesn't spray fuel on the valves, so deposits can happen if any liquid/vapor falls out of suspension and lands on the valves.

In other vacuum pump systems, like say a vacuum brake bleeder, you always put a can in between the actual pump intake and whatever you want to apply vacuum to--in this example a brake bleeder nipple. Any liquid that is being sucked will fall into the can before it goes into the pump inlet (assuming of course the pump inlet port on the can is at or near the top of the can). If my 10th grade physics hasn't failed me, the can acts as an expansion chamber and allows heavier fluids than air or other gasses to slow down and settle out via gravity, while not affecting the vacuum pressure (or at least no more than a negligible pressure difference). That can on the brake bleeder pump serves to protect the pump from ingesting liquids which might ruin the pump. Ditto on other vacuum pumps.

A catch can operates on the same principle. As intake vacuum sucks everything out of the crankcase, the catch can acts as that expansion chamber, causing vapors, mists, and other stray liquids to fall out of suspension and into the bottom of the catch can as the speed of the fluids through the catch can drop (even though the vacuum pressure remains constant). All you have to do is clean the can regularly so it doesn't fill up (every oil chance suffices on mine), or get an automatic-emptying one. They might not be 100% perfect, but they do work.

What do you think of the BMS “zero maintenance” catch cans?

 

[AusStinger]

What do you think of the BMS “zero maintenance” catch cans?

IMO, avoid this type.
Crank case vapours are a mixture of fuel and oil which is something you don't want to reintroduce to your oil system. Its better to remove that stuff than reintroduce it to your lubrication system.

Also, the position of this item when installed and being made of metal, makes me believe it 'could' heat the vapours to a dangerous point in a worst case scenario.

 

[LordKOTL]

What do you think of the BMS “zero maintenance” catch cans?

There are some here on this board who swear by them; I'll let them chime in on the pros and cons of them.

In my case, I take the same stance as @AusStinger : crankcase vapors are not just oil. There could be fuel, water, or other things I personally don't want that gunk in my oil sump, mixing with my oil and trying to lube up things like my turbos. From my 1000-3000 mile oil change (only at 4100 miles now), it collected about a shotglass of gunk (yummy.). I figure for a 3k interval it won't pass 1/4 cup (Freedom Unit) of gunk, and my catch can has way more volume than that. As long as she runs liked a dream, if I empty it every time I change my oil, I should be fine.

 

[AusStinger]

Back in the 70's car manufacturers would put one of these in the PCV line which did virtually the same thing as the BMS unit but was a much cheaper ( and probably safer ) alternative.

 

[Anunakie]

So which catch can is better or would you guys recommend? The Mishito or the ADD W1 V3.3?

 

[Thomby]

IMO, avoid this type.
Crank case vapours are a mixture of fuel and oil which is something you don't want to reintroduce to your oil system. Its better to remove that stuff than reintroduce it to your lubrication system.

In my case, I take the same stance as @AusStinger : crankcase vapors are not just oil. There could be fuel, water, or other things I personally don't want that gunk in my oil sump, mixing with my oil and trying to lube up things like my turbos. From my 1000-3000 mile oil change (only at 4100 miles now), it collected about a shotglass of gunk (yummy.).

Isn't the idea that volatile gasoline & water vapor will pass through to the intake, while oil mist will hit the filter and drain back into the crankcase?

Unless you have ridiculous amounts of blowby, at operating temp any gasoline or water in your crankcase should be in gas form above the oil, not liquid mixed into it. It will vent through the PCV, with a small amount of (liquid) oil mix. The latter is what bakes onto the back of your intake valves.

 

[LordKOTL]

Isn't the idea that volatile gasoline & water vapor will pass through to the intake, while oil mist will hit the filter and drain back into the crankcase?

Unless you have ridiculous amounts of blowby, at operating temp any gasoline or water in your crankcase should be in gas form above the oil, not liquid mixed into it. It will vent through the PCV, with a small amount of (liquid) oil mix. The latter is what bakes onto the back of your intake valves.

It's the condensates. Anything in a gaseous state should pass through like feces through a cobra chicken. I believe the mist/condensates/particulates that get caught aren't 100% engine oil. They might get caught in the oil filter, but personally, I don't want that gunk getting near my turbos.

Again, your car, YMMV.

 

[AusStinger]

Isn't the idea that volatile gasoline & water vapor will pass through to the intake, while oil mist will hit the filter and drain back into the crankcase?

That's the idea of a zero maintenance setup but I'd prefer that the fuel degraded oil not return to the sump.
Draining the catch can every now and then is my preference.

 

[AusStinger]

So which catch can is better or would you guys recommend? The Mishito or the ADD W1 V3.3?

That is up yo you.

I think the ADD W1 setup is more comprehensive but I really don't like the mounting setup.
I have the Mishi can and I like it. If they had made one for the clean side I would have purchased that also.