DIY catch can material?

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I didn't get a response in older related thread, so I will try again.

I have two different catch cans connected sequentially in my Tahoe. That works well, but now I'd like a catch can in our Mazda, and I will transfer this setup there.

I am thinking about building a large catch can out of 3 or 4" DWV copper pipe, with copper tube going almost all the way to the bottom, and steel wool in the middle. Maybe even the accending spiral out of steel wool. I think copper will work better then PVC water pipe for heat transfer.

I don't have space constraints under the hood of Tahoe for this purpose. Maybe I will even place it under the bumper cover or in the wheel well.

My question is about copper as a suitable material. Is it acceptable for that application? Would the metal react in some way with catched stuff that would produce some chemicals detrimental to the engine internals? Would copper corrode in contact with steel wool and caught water?

Maybe stainless exhaust flex pipe or straight tubing will work better? Thick walls though...

Also, would PVC clear vacuum hose work PCV with gases? Thinking about 3/4 ID hoses to lessen restriction...

Thank you for your help!
 
Copper would transfer heat better, which is what i would not want. I would want as little heat in the catch can as possible.
i mean you want the water and oil vapor to condense in the catch can and not move on to the intake. For that , the catch can needs to be cooler, a copper pipe seems like it would conduct more heat to the center of the catch can.

I wonder if something like this on the catch can would make it condense better.

51chcRZ0GZL.jpg
 
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Hmm, I thought otherwise about heat transfer... I guess, it depends on the can's location. Sump gases should be quite warm at operational temperature. Warmer then under the hood in any case. Warmer still then in the wheel well or behind the bumper cover... So it appears to me that the heat transfer would be from the core to the outside.
But I agree, something to think about.
 
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The copper will corrode somewhat but I don’t know if if would be a problem. I doubt it though. Use stainless steel wool.

If you could put it outside of the hot under hood area, it would really help with condensing the liquids. There you would want it to be a highly conductive material. Under the hood, that property is less important. The gasses flowing through it there are probably warm and the underhood air is somewhere between cold and hot, depending on ambient temperature and engine temperature.
 
Originally Posted By: yugrus
I Would copper corrode in contact with steel wool and caught water?



Nope, because the steel wool, being lower in the electrochemical series, will corrode for both of them, unless stainless.

For the rest, you don't give dimensions, but you want something thin walled, to give good heat transfer.

Beer can.
 
In Oz, a lot of the 4 wheelers are making theirs out of PVC piping, and open pore foam.

When it comes to catching mist, the bigger the expansion ratio the better.

Read your post earlier, and have been pondering.

You could put a remote oil filter mount, and put the biggest, cheapest oil filter you can find on it (no ADBV). The filter media will coallesce the oil droplets, which will ultimately fall to the bottom.

Unscrew and dump, or unscrew, throw away, and replace.
 
Thank you for suggestions gents!
Few years ago I experimented with air compressor filter as catch can, and found that using its native filtering media was impractical. It gets clogged really fast, impeding the flow. So remote oil filter is a good approach, but I guess, filter itself should be cut, hollowed and its internals modified. I agree that the expansion ratio is very important here. I think big filters are still smaller then what I have in mind, diameter - wise. Are there any with 3-4" ID? With 3/4" ID central inlet pipe that should give me good expansion ratio at 8-10" container length or more.

As for beer can, good thin wall container, but not long enough, even the bigger one, and cumbersome to make serviceable.

Stainless wool is a great idea!

I'm curious if I go with thin-wall copper pipe, the copper would show in UOA, implying the reaction with PCV gases. Maybe this would mean nothing, maybe otherwise. I just don't know.

I can also take stainless exhaust pipe and mill the walls thinner. Can't solder end-cap on that though. Can MIG it, probably. Depends on how thin the steel is.

Another thought was the addition of the electric vacuum pump to maintain constant vacuum in the sump. I'd use the check valves at the intake and the pump, the T-connector, and the pressure transducer. The pump would only kick in when the intake vacuum drops, maintaining proper increased PCV flow evacuation, sealing piston rings, etc. Looks like this is what the stock PCV system is lacking at higher RPMs. Intermittent nature of the pump operation should prolong it's life, and the system is fail-safe. The pump would vent into the atmosphere or into exhaust post-cat. Providing that the catch can does its job, the vented gas should be harmless. I would need to tune it for the transitional period of low vacuum, so that at least something creates it in the sump whatever the engine is doing.

I'm really open for suggestions at this point, thank you all very much!
 
BTW, "air/oil separators" for small aircraft are a simple aluminium can with plain aluminum window screen, cut to width the same as the length of the can (about 6" or so) and just wrapped around a small wooden dowel and rolled up until the roll will fit inside the can. Pretty simple.

On these, you have:
1) airflow (with oil also) going in
2) airflow out
3) drain back to the sump

m300.jpg
 
http://www.google.co.uk/url?sa=i&rct=j&q=vacuum%20pump%20catch%20can&source=images&cd=&ved=2ahUKEwjVt6byl4XaAhXRfFAKHX1SCu4Qjxx6BAgAEAI&url=http%3A%2F%2Fwww.stangtv.com%2Ftech-stories%2Fengine%2Ftech-gz-motorsports-vp104-super-pro-33-cfm-vacuum-pump%2F&psig=AOvVaw17MYs-7fiiiLq0HJ2zzhJL&ust=152198866823391
 
i bought 2 Kobalt cans like krismoriah72 listed. but not in yet. BUT could you use a small industrial air pump and just dump the air over board?
 
You sure can, but this is not politically correct, it will drip all over your driveway, and it smells like you know what...
Gotta look into that Cobalt thing. Looks like it should be easy to modify. And the sight glass is nice. Smaller yet then I wanted. And I bet it is quite heavy!
Aircraft separators are also too small for my taste. I don't like the idea of the condensation recycling though. But this outlet could be plugged and used as the drain cock.
 
Originally Posted By: Ducked
I suppose a beer can might collapse if it sees negative pressure though.
Which it certainly will.
 
My first home made one was a 10" piece of 3" aluminum with a plastic baffle running down the middle, two 3" rubber plumbing caps and two 3/8" 90* plastic hose barbs. I had it in the fender area and horizontal. I also had a spring loaded check valve that opened when the vacuum was ~0"Hg and was self draining, closed under normal intake vacuum. I also plugged the air intake for the PCV system and then the intake was under 7"-9"Hg vacuum at idle or cruising. This would close the check valve.

I just use the cheap eBay ones now.
 
I was thinking about self-draining check valve, but decided against it. I think it would stain the driveway and might freeze in the winter. There's lots of water in the can when it's cold. I will actually use electric pipe heater for the can and hoses, so the catch can gets pre-heated when the engine and transmission do.
I should think about horizontal can some more. Gives you twice the path.
 
It does freeze in the winter but what I had could hold quite a bit. Freezing catch cans can be a bit issue on a turbo car.

The PCV side will not permanently stain the drive as little of it is actual oil. Mostly gas vapor and water. It would take a week or so to evaporate but leave no stain.

catchcan_installed.jpg
con_can_drippins.jpg
con-can-standing-looking-at-baffle-5.jpg
 
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