Catch Can Skeptic

[Shakeydeal]

I've asked two very reputable mechanics in my area what they thought of a catch can for DI engines. Neither of them had ever heard of it.

 

Shakey

[SS502]

1 minute ago, Shakeydeal said:

I've asked two very reputable mechanics in my area what they thought of a catch can for DI engines. Neither of them had ever heard of it.

 

Shakey

Wow...without saying yeah or neigh on needing one, Catch Cans have been around for decades.

[Shakeydeal]

I was a little surprised too. But one guy was a BMW master mechanic and I was inquiring about a 335i I had at the time. That said, it didn't diminish my respect for him because he was a BMW fanatic through and through and I continued to take my car to him until I sold it.

 

Shakey

[SS502]

6 minutes ago, Shakeydeal said:

I was a little surprised too. But one guy was a BMW master mechanic and I was inquiring about a 335i I had at the time. That said, it didn't diminish my respect for him because he was a BMW fanatic through and through and I continued to take my car to him until I sold it.

 

Shakey

That surprises me even more LOL...BMW has had issues that many of those owners use to justify the installation of a catch can. Even before the GM DI engines. The BMW S55 engine has an air oil separator in the PCV system that returns oil back to the sump, this is doing the same thing an external catch can does minus dumping back into the sump. NOT arguing Shakey, just surprises me they/he said that. I would bet my pink slip that more BMW owners run catch cans than K2 owners.

[Jacoby]

Not to get off subject but mechanics are morons, well some of them anyways.  The below example is why I will do every bit of work I can on my vehicle if Im able. 

 

Last week when I was going through my swapping oem coil springs from the oem strut to my new lifted struts, I thought I would hit up the local do it all auto shop.  They said sure we do struts all the time and have a spring compressor and what not.  "take us a half hour" they said.  Dude calls me a hour later says our compressor cant compress the spring enough to put the nut on the shock rod and top spring mount.  I thought hmm that's weird.  I went up there and what I witnessed blew my mind.  They were trying to compress the spring down to damn near a pancake so they could mount it on a COMPRESSED strut.  Anybody who's ever bought shocks/struts before knows they are boxed compressed.  That way they can fit in smaller boxes.  When you open them and get ready to install them you usually twist the shock rod and it uncompresses and the shock extends.  These idiots didn't know that and shocks/strut replacement IS A SERVICE THEY OFFER for cryin out loud.  I asked the guy if he let the shock rod all the way out and he said that's as far out as it goes.  I asked for a pair of his pliers and proceeded to twist the rod maybe a quarter of a turn and the rod started to extend out.  Dude actually sat there and told me they weren't supposed to do that then asked me if I wanted them to try and mount the springs again free of charge.  I grabbed all my stuff and high tailed it right out of there. 

[KARNUT]

Not to get off subject but mechanics are morons, well some of them anyways.  The below example is why I will do every bit of work I can on my vehicle if Im able. 
 
Last week when I was going through my swapping oem coil springs from the oem strut to my new lifted struts, I thought I would hit up the local do it all auto shop.  They said sure we do struts all the time and have a spring compressor and what not.  "take us a half hour" they said.  Dude calls me a hour later says our compressor cant compress the spring enough to put the nut on the shock rod and top spring mount.  I thought hmm that's weird.  I went up there and what I witnessed blew my mind.  They were trying to compress the spring down to damn near a pancake so they could mount it on a COMPRESSED strut.  Anybody who's ever bought shocks/struts before knows they are boxed compressed.  That way they can fit in smaller boxes.  When you open them and get ready to install them you usually twist the shock rod and it uncompresses and the shock extends.  These idiots didn't know that and shocks/strut replacement IS A SERVICE THEY OFFER for cryin out loud.  I asked the guy if he let the shock rod all the way out and he said that's as far out as it goes.  I asked for a pair of his pliers and proceeded to twist the rod maybe a quarter of a turn and the rod started to extend out.  Dude actually sat there and told me they weren't supposed to do that then asked me if I wanted them to try and mount the springs again free of charge.  I grabbed all my stuff and high tailed it right out of there. 

You started it my turn. Bought a new lawnmower, got it home belt broke. They sent a ( tec. guy). After watching for a 1/2 hour I told him to step back and I put it on. The diagram was right there, he couldn’t figure it out.


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[1SLOW1500]

Wow...without saying yeah or neigh on needing one, Catch Cans have been around for decades.

It's like asking gm if its needed. Even if it is they aren't going to say yes because the next question is then why isn't it included. I have friends that are the best mechanics around. Start talking performance or aftermarket they are lost. They are nothing more then a useful tool. They can do there job with the knowledge and support of the manufacturers, outside that dont expect much.

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[Grumpy Bear]

Were builders using catch cans on carbureted motors? Not really. This whole thing rest on the idea that detergents in gasoline stop inlet valve deposits. Cars have had PCV systems that feed back to the inlet for a very long time. In that time there have been plenty wet runner motors torn down with inlets plugged to the point of throttling the motor. And yet most did not. In those wet runner motors the usual culprit was excessive inlet valve seal leakage. So is it the fact that detergents are not available in a dry runner motor OR excessive amounts of oil in the inlet runner are present. It's a question worth the ask. For one, a catch can is a cure for the other it's a band-aid on a GSW. 

 

Under what conditions, operational or mechanical, is there enough oil in the inlet system to plug an inlet to the point of air deprivation? How did cups of oil trapped in a can get to be 'normal'? 

 

What is getting missed it the 'degree' of oil intrusion. Motors with bad rings that use measurable and excessive amounts of oil suffer the type of blow by that pushes PCV systems to the brink. Well sealed rings under normal loads display very little vapor traffic in a multi-cylinder motor.  It takes traffic at a high enough velocity to carry oil mist anywhere. The 14 and newer motors have incredible amounts of cover baffling and mist separation built into them. 3X as much as pre 2014 motors. 

 

That said if you have enough oil to trap and show by the cup the yes, use a can...BUT why is there that much to begin with? 

[EpicLT]

I want to say that I personally don’t run one (yet?) but I can’t ignore all of the stories of people draining them. I guess I feel like it’s beneficial to not let that get back into the engine to be burned up. Regardless, my dad’s company uses GM exclusively for their fleet trucks (all Silverados) and the 2016+ models now have 50-60k on them. Their engines haven’t blown up yet from being clogged but I’m not knowledgeable enough in this topic to know when buildups would actually hurt. 

[SS502]

1 minute ago, EpicLT said:

I want to say that I personally don’t run one (yet?) but I can’t ignore all of the stories of people draining them. I guess I feel like it’s beneficial to not let that get back into the engine to be burned up. Regardless, my dad’s company uses GM exclusively for their fleet trucks (all Silverados) and the 2016+ models now have 50-60k on them. Their engines haven’t blown up yet from being clogged but I’m not knowledgeable enough in this topic to know when buildups would actually hurt. 

Well, I am not sure one would ever blow up on you lol. IF there is a carbon build up, and again I am not promoting a CC or disputing them but IF you have carbon build up you will or can lose proper air flow into the cylinder leading to decreased fuel economy and or performance, rough idle or if a chunk breaks off and is ingested possible cylinder damage. If it made it through the combustion chamber then it could in theory get stuck and damage your catalytic converter. These are all my opinions. I'm gonna have to put that disclaimer that Jacoby puts in his signature block into mine LOL.

 

[EpicLT]

Just now, SS502 said:

Well, I am not sure one would ever blow up on you lol. IF there is a carbon build up, and again I am not promoting a CC or disputing them but IF you have carbon build up you will or can lose proper air flow into the cylinder leading to decreased fuel economy and or performance, rough idle or if a chunk breaks off and is ingested possible cylinder damage. If it made it through the combustion chamber then it could in theory get stuck and damage your catalytic converter. These are all my opinions. I'm gonna have to put that disclaimer that Jacoby puts in his signature block into mine LOL.

 

Thanks for the reply. I do my own routine maintenance, but that’s about my extent of engine knowledge. Electronics is more down my alley. I wish I knew more about engines. 

[xax]

Just get your intake walnut blasted at 100k Miles and be done with it. The engine isn't going to fail from having no catch can... 

18 hours ago, CSI-WALLEYE said:

 

[MaverickZ71]

Just think about all of this crap today.  Back in the day, a simple valve cover breather used to take care of everything.  But that's against the law now.  The more mankind 'progresses', the more we move backwards.  Really torques me off that my truck doesn't run as well as it could because of oil in the intake, supposedly for air quality, when meanwhile over in India/Pakistan/China, etc., they're doing whatever the he11 they want and polluting more than we ever did.  And the liberals driving our environmental laws have no problem flying everybody they know to the islands for vacations on the taxpayer dime.    

Edited April 1, 2019 by MaverickZ71

[Shakeydeal]

14 hours ago, MaverickZ71 said:

Just think about all of this crap today.  Back in the day, a simple valve cover breather used to take care of everything.  But that's against the law now.  The more mankind 'progresses', the more we move backwards.  Really torques me off that my truck doesn't run as well as it could because of oil in the intake, supposedly for air quality, when meanwhile over in India/Pakistan/China, etc., they're doing whatever the he11 they want and polluting more than we ever did.  And the liberals driving our environmental laws have no problem flying everybody they know to the islands for vacations on the taxpayer dime.    

 

Amen brother.....!

 

[Capt Bob]

18 hours ago, Grumpy Bear said:

 That said if you have enough oil to trap and show by the cup the yes, use a can...BUT why is there that much to begin with? 

Well then in an effort to stay on point, it appears by this statement that if your engine is in good shape, you should have minimal oil in the blow-by gas so the question is.....

What constitutes "minimal"?

I read an article on emission system design that stated that an engine in fine tune should have a measured blow-by oil content of 1gram or less per hour under load. That would equate to a little over 3.5 ounces every 100hrs. if I did the math correct. One might want to measure the can droppings based on an hourly drain rather than mileage to see if they're in that ball park.

If the results are higher, then logic would indicate a poorly designed motor or bad sealing aka rings. I'm leaning toward the latter. If so then the use of quality oil and filter with consistent change times may provide just as much protection as the can itself. A lot to ingest and think about with these motors.