Catch Cans - What's the Verdict?

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Originally Posted by MrHorspwer
Originally Posted by shimps1
As long as I remember to empty it, is there any way that it can cause damage to the engine?
What's the worst that can happen? When it gets really cold, moisture that has condensed in the line freezes, plugging the PCV system, causing excessive crankcase pressure, and blowing a front or rear crank seal. That's about the worst that can happen.
How does a catch can affect that one way or the other?
 

shimps1

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One of my concerns is, are catch can's self-fulfilling? As in, does installing a catch can increase the vapors, thus allowing the catch can to look useful? Are they lower resistance than the stock PCV system, thus allowing more stuff into them?
 
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Atlanta,GA
Originally Posted by shimps1
One of my concerns is, are catch can's self-fulfilling? As in, does installing a catch can increase the vapors, thus allowing the catch can to look useful? Are they lower resistance than the stock PCV system, thus allowing more stuff into them?
No. All engines generate blow-by gases which are vented back into the intake to get burned off. The amount of blow-by and the effectiveness of the technology used to condense the oil mist varies from one manufacturer to another.
 
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5,186
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Atlanta,GA
Originally Posted by The_Nuke
Originally Posted by MrHorspwer
Originally Posted by shimps1
As long as I remember to empty it, is there any way that it can cause damage to the engine?
What's the worst that can happen? When it gets really cold, moisture that has condensed in the line freezes, plugging the PCV system, causing excessive crankcase pressure, and blowing a front or rear crank seal. That's about the worst that can happen.
How does a catch can affect that one way or the other?
The catch can and the associated hoses become part of the PCV system. The risk is higher the farther away from the engine you have to mount the can because you need longer runs of hose and the system will heat up slower. A solution in search of a problem.
 
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3,131
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Western S.C.
Originally Posted by BMWTurboDzl
Originally Posted by shimps1
One of my concerns is, are catch can's self-fulfilling? As in, does installing a catch can increase the vapors, thus allowing the catch can to look useful? ...
No. All engines generate blow-by gases which are vented back into the intake to get burned off. The amount of blow-by and the effectiveness of the technology used to condense the oil mist varies from one manufacturer to another.
True, but water vapor is a major component of that blowby mixture, so in cold weather more water will condense in the can, which might make it "look useful," depending on the owner's perspective. The same water vapor would normally pass into the intake uncondensed.
 
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D/FW Metroplex
Originally Posted by BMWTurboDzl
Originally Posted by The_Nuke
Originally Posted by MrHorspwer
Originally Posted by shimps1
As long as I remember to empty it, is there any way that it can cause damage to the engine?
What's the worst that can happen? When it gets really cold, moisture that has condensed in the line freezes, plugging the PCV system, causing excessive crankcase pressure, and blowing a front or rear crank seal. That's about the worst that can happen.
How does a catch can affect that one way or the other?
The catch can and the associated hoses become part of the PCV system. The risk is higher the farther away from the engine you have to mount the can because you need longer runs of hose and the system will heat up slower. A solution in search of a problem.
I see...not really, but it's not worth arguing about. The 3.5L in my last Challenger absolutely benefitted from a catch can. That's not something I will ever debate. The 5.7L in my current Charger may or may not benefit from it. It certainly won't hurt it, as I haven't seen freezing temps here since January I think, and even then they got nowhere close to zero. I'm not willing to acquiesce and give credence to your assertion, but I'm not prepared to debate it either seeing as it doesn't apply to me. Nuke
 
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5,186
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Atlanta,GA
Originally Posted by CR94
Originally Posted by BMWTurboDzl
Originally Posted by shimps1
One of my concerns is, are catch can's self-fulfilling? As in, does installing a catch can increase the vapors, thus allowing the catch can to look useful? ...
No. All engines generate blow-by gases which are vented back into the intake to get burned off. The amount of blow-by and the effectiveness of the technology used to condense the oil mist varies from one manufacturer to another.
True, but water vapor is a major component of that blowby mixture, so in cold weather more water will condense in the can, which might make it "look useful," depending on the owner's perspective. The same water vapor would normally pass into the intake uncondensed.
I'm thinking of the integrated oil separator installed by the automaker. For example BMW places theirs inside the valve cover itself.
 
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5,186
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Atlanta,GA
Originally Posted by The_Nuke
I see...not really, but it's not worth arguing about. The 3.5L in my last Challenger absolutely benefitted from a catch can. That's not something I will ever debate. The 5.7L in my current Charger may or may not benefit from it. It certainly won't hurt it, as I haven't seen freezing temps here since January I think, and even then they got nowhere close to zero. I'm not willing to acquiesce and give credence to your assertion, but I'm not prepared to debate it either seeing as it doesn't apply to me. Nuke
Ya, probably not an issue in Texas but could be in Chicago or the NE US. A simple Google search will show you.
 
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Kingston
Originally Posted by BMWTurboDzl
Originally Posted by CR94
Originally Posted by BMWTurboDzl
Originally Posted by shimps1
One of my concerns is, are catch can's self-fulfilling? As in, does installing a catch can increase the vapors, thus allowing the catch can to look useful? ...
No. All engines generate blow-by gases which are vented back into the intake to get burned off. The amount of blow-by and the effectiveness of the technology used to condense the oil mist varies from one manufacturer to another.
True, but water vapor is a major component of that blowby mixture, so in cold weather more water will condense in the can, which might make it "look useful," depending on the owner's perspective. The same water vapor would normally pass into the intake uncondensed.
I'm thinking of the integrated oil separator installed by the automaker. For example BMW places theirs inside the valve cover itself.
I had my catch can on my 83 Caprice all winter, in temperature as low as -22 celsius or so, and I had no issues. It's also mounted fairly far from the engine, which doesn't build much heat under hood even in the summer time. There is a lot of open space under the hood since I removed all the AC years ago. I'm not saying it can't happen, but it didn't happen to me. In my case any damage wouldn't be very expensive to fix on a small block Chevy v8 though.
 
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I have a question (I'm not the ICE or car mechanic guru but have friend and family who are, and this is somewhat a proxy inquiry based on discussions where this has come up) On the modern car (DI specifically), is this atomized crankcase oil mist a necessary component of the vehicles "combustion process" (factored into the burn process in some significant way necessary for proper operation) OR Is this atomized crankcase oil mist basically a "tramp" vapor that is simply being "incinerated" during the combustion process for emission control, relieving crankcase pressure etc? In my mind, the correct answer to that question will effectively address and answer the question as to whether a catch can is necessary as well as to what level of benefit having one may be as opposed to not having one. From industrial machines, I design and install mist collectors (basically what we call PCV systems) for safety, air quality etc. but the applications are not "engines" and have combustion blow by ( but the system would capture them as well) This technology is well recognized and effective ( assuming its designed and built right) So, in my mind the "verdict" on the technology proper is a clear and inarguable YES at to whether the technology is legitimate, valid, applicable and proven to work as designed. Then the question evolves to "does it either mitigate a risk (such as coking valves) or does it add a benefit (or a mixture of both) There could be a split verdict- it "does" mitigate a risk but at a cost. I believe the key to both is the specific answer on what those gases do, add or produce during the combustion process. Granted this is just me thinking but if I were going to analyze it, that would be the first datapoint I would want to nail down.
 
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Jupiter, Florida
Originally Posted by littlehulkster
Your PCV system is already precisely tuned by actual engineers and most cars have some sort of separator on them anyway.
It's nice to believe that every aspect of a vehicle is well engineered. However, anybody who spends time in dealership repair shops knows there are common (and unnecessary) problems that continue to show up. Some vehicles even vent blowby to turbocharger inlets, contaminating the compressor and the intercooler. A quality catch can will solve this problem and prevent frequent cleanings. I'm not convinced a catch can will prevent intake valve deposits. But a quality synthetic oil can, in some circumstances, help or eliminate the issue.
 

JTK

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Buffalo, NY
The way I see it is, you can spend $5 or $500 on one. They're ALL going to catch liquids, but none of them are going to stop all vapors from going back into the intake manifold and combustion chamber. Could they buy you some time between intake valve cleanings on a DI engine? Maybe. Not sure we have real before/after data to support it though.
 
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Originally Posted by Cujet
I'm not convinced a catch can will prevent intake valve deposits. But a quality synthetic oil can, in some circumstances, help or eliminate the issue.
Nor am I but the key to prevention is to assess the formation of the deposits and remove as many of the causal factors as necessary. I ask this if anyone knows. On the "coking" process ( layering of the deposit) Is the heat of the valve drying it from contact outward ( this would create a more striated layer pattern with the denser material on bottom) and it builds from the bottom up or Does ambient heat "cook" it to the stem? That would go a long way in devising ways to deal with it- anyone know or have investigated this?
 
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I believe they make the most sense for forced induction motors with intercoolers. The engines produce more blow-by under boost and the oil vapors make the intercoolers less efficient when they coat the fins. The vapors can reduce octane and encourage knock, as well.
 
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I fitted a catch can to my Volvo a couple of months ago. Anyone who has a turbo a few years old, petrol or diesel, will have seen the oil around the turbo intake, leaking out around the hose. I fitted this catch can to my Pajero many years ago, just to see how much oil was actually going through the turbo...not much it turned out. The Volvo already has a factory catch tank, my PCV system is working, but there is oil at the turbo inlet, and creamy goop at the PCV inlet to the hose. Very few miles over lockdown, and it was all close to home, but back at work for 7 days now, and checked the tank - it was nearly full ! 99% water with a very small amount of cream, so hardly any oil at all. I don't know if I want to drain water from this tank every week....and what if I forget ? I think I've reproven what I proved 15 years ago - it's mostly water that condenses, so not a problem. The Volvo system works well at recycling the oil vapour back to the sump, and passing the H2O to the intake. It comes off tomorrow.
 
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Originally Posted by ABN_CBT_ENGR
... I ask this if anyone knows. On the "coking" process ( layering of the deposit) Is the heat of the valve drying it from contact outward ( this would create a more striated layer pattern with the denser material on bottom) and it builds from the bottom up or Does ambient heat "cook" it to the stem? That would go a long way in devising ways to deal with it- anyone know or have investigated this?
Is it a useful hint that Mazda claims to have minimized the issue by designing their engines to maintain higher intake valve temperature?
 
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Originally Posted by CR94
Is it a useful hint that Mazda claims to have minimized the issue by designing their engines to maintain higher intake valve temperature?
A Clue! Leads me to believe that someone has studies it to a degree and realizes that there is a line between burning and true incineration and they are trying to get there to resolve the issue. A car engine doesn't have the metallurgy or density and flow to match the temp and soak time to incinerate oils so they appear to be attempting to get as close there as they can. Then they would need to address the source oil in terms of volume and origin. If its not "flashed" off then some residue will stick and accumulate. ( even then some residue will be there- no such thing as perfect incineration) But I would think this would also have the end effect of making whatever remains much harder to clean because it would be like a baked ceramic now Would make an interesting study ( and I am certain it is being or has been or both)
 
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Texas
Hey guys. Bumping an old thread here as I wanted to share some information on the topic... nothing scientific just a real-world sample. So I put an Elite Engineering E2-X catch can on my 2016 L86 Yukon XL Denali when I bought it new... can went on around 300miles in. I did not install the clean side separator. I used Mobil1 0w20 Annual Performance and M1-113A filter... changed the oil and filter every 4k miles (don't flame me for wasting money). I've recently switched over to Amsoil Signature full synthetic 0w20 and Amsoil filter as well. Should also note, I've been running a tune and have had DOD disabled from day 1.

Okay, details out of the way, I took my intake manifold off this past weekend as the curiosity got the best of me and I wanted to see what the valves looked like. Behold the results. Note, the valves got cleaner as you worked you way to the rear of the engine. I should confirm, I'm right at 54,500 miles. Curious what you all think. Just wanted to share this use case from a vehicle that has basically had a can on it from the start as the only owner. I was pretty tired from the gymnastics session in and out of the engine bay so apologies the pictures aren't professional. was having trouble holding a light, my phone and not end up falling out on to the garage floor :)

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