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The new "definitive catch can" thread

 
Old 03-12-2019, 05:06 PM
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Originally Posted by Savington View Post
A check valve right after the PCV valve is good practice in all applications.

It is also worth mentioning that if you use the car on track, you should consider capping the PCV/intake side breather entirely, or be prepared to constantly drain catch cans connected to that side (like every few laps). For all 94-00 motors, you can and should simply block the PCV valve and run a breather from the driver's side only. For VVT motors, a much more complex air/oil separation system is sometimes required.
Can you expand on the track VVT solution?
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Old 03-12-2019, 05:06 PM
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Maybe my significant modifications to open up the cold side valve cover gallery helped or I don't corner to the left with as much vigor as others, but I'm not having difficulty with oil entering the catch can with both sides plumbed to it.
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Old 03-12-2019, 05:37 PM
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Originally Posted by AutoFreak57 View Post
Can you expand on the track VVT solution?
I'd rather not, sorry. The R&D was not cheap. If you have a VVT motor and it's puking its guts out for seemingly no reason, feel free to email me and I'll be happy to set you up with the proven solution.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 03-12-2019, 06:05 PM
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Originally Posted by sixshooter View Post
Maybe my significant modifications to open up the cold side valve cover gallery helped or I don't corner to the left with as much vigor as others, but I'm not having difficulty with oil entering the catch can with both sides plumbed to it.
Or location of your can and tubing that allows oil to drain back before being deposited into the can?
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Old 03-12-2019, 06:40 PM
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Originally Posted by DNMakinson View Post
Or location of your can and tubing that allows oil to drain back before being deposited into the can?
Large diameter openings and hoses slow down the airflow and allow the oil to fall out of suspension and drain back rather than being propelled. The internal baffle openings and all fittings and hoses are much larger than stock. The aluminum bungs welded into the intake are 1/2 NPT thread and the hoses are 5/8in. Yes, the cold side comes out of the VC at a 45 degree angle and goes over the intake, so oil could drain back if falling out there.
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Old 03-12-2019, 06:40 PM
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Here's a question for you folks to ponder. Do you put scrubbing material (some kind steel wool or the like) inside the valve cover chamber (hot side)? I say no, because you really don't want any of the fuel/water blowby to come out of suspension (mist) before it leaves the VC. You want to catch it later in that super awesome catch can.

ALSO - I think we need to make sure everyone is clearly stating NA or FI. I'd like to start this thread: "The definitive catch can when you have 400hp and loose ring gaps and piston clearances"
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Old 03-12-2019, 06:49 PM
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Originally Posted by Mudflap View Post
Here's a question for you folks to ponder. Do you put scrubbing material (some kind steel wool or the like) inside the valve cover chamber (hot side)? I say no, because you really don't want any of the fuel/water blowby to come out of suspension (mist) before it leaves the VC. You want to catch it later in that super awesome catch can.
There have been a few threads which have addressed that question. One I linked to at the bottom of the first post: https://www.miataturbo.net/engine-pe...ication-54742/ (In that thread, note that I don't approve of Jason's choice of plastic kitchen scrubbers. Coarse stainless steel or copper kitchen scrubbers are more common.)

One word of caution: many of these materials can shed fibers, which can then (theoretically) fall back into the head and get onto lifter surfaces and such.
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Old 03-12-2019, 08:02 PM
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On what is primarily but not wholly a track car, over the last 5 trackdays, despite only driving to either the track or to somewhere to do work on the car (ie to mapping + alignment), my dash tells me I've only racked up 3 hours of time in positive boost, yet I've somehow racked up 70 hours of engine on time. This makes me think I should consider reconnecting the PCV side.

My PCV experience with this car (relatively fresh forged VVT turbo, ~250whp)
Setup 1 - 323 GTX PCV installed but VTA, IM blanked, filter on exhaust side port
I only did a short track shakedown with this setup, but it spat out oil quickly enough that it covered my windscreen in a few laps (thanks vented hood...) and when I made a makeshift catch can from a water bottle, it filled pretty quickly.

Setup 2 - 323 GTX PCV still installed but VTA, IM blanked, AN10 bung welded on top of exhaust side of cam cover into 1 liter unbaffled catch can with breather
5 trackdays later, I am still yet to empty the catch can because it is still yet to register sufficient oil on the level.

Edited to add,
I now have a pretty leaky front crank seal. I suspect it to be caused by the dodgy batch of Boundary ones a few years ago, but not having a slight crankcase vacuum for all those hours not in boost, may be a factor.

Last edited by Tran; 03-12-2019 at 08:07 PM. Reason: Crank seal info
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Old 03-12-2019, 08:49 PM
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Joe - not questioning what to use for scrubbers. I'm saying we should not use them at all in the VC if the intent is to vent all that gas/water saturated air out of the engine.
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Old 03-12-2019, 09:31 PM
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Originally Posted by Mudflap View Post
Joe - not questioning what to use for scrubbers. I'm saying we should not use them at all in the VC if the intent is to vent all that gas/water saturated air out of the engine.
This is an area in which I don't have enough practical experience to form a definitive opinion.

In a highly-boosted track engine, we can assume that oil changes will be frequent enough that:
  • Oil loss due to a lack of baffling will be low enough that it will be easily compensated for after the end of the race, and yet
  • Oil changes will be frequent enough that recaptured condensate is of essentially no consequence.
At the other end of the spectrum, with a street-driven car, we can assume that:
  • Oil loss due to a lack of baffling will be of consequence due to the inspection / change intervals involved, and yet
  • At the temperatures experienced at the top of a head at normal operating temperature, water vapor is unlikely to condense into liquid no matter how much metallic packing material is present between it and the outlet to the air / oil separator or breather tank.

In a hypothetical environment, both scenarios suggest that packing material within the valve cover either causes no harm or provides a benefit.

That said, I'll restate that I'm not an engine-designer or mechanical engineer. The OEM design does not incorporate packing material, but then, it also does not presuppose high-boost, high-RPM operation.


I'd love to see empirical data on this topic. To date, I have found none.


EDIT: Jesus tap-dancing Christ, this new message editor is fighitng me at every step. I apologize for the bullet list not being properly spaced and intended. I literally cannot figure out how to cheat the editor into making me let it happen.)
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Old 03-12-2019, 10:06 PM
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It’s worth noting that I’ve tested five different PCV valves with a turbo setup, including the standard Mazda OEM and the 323 GTX, and all of them allowed boost to leak by which pressurizes the crank case (and in my case pops the dipstick). Capping the PCV system yielded a 2-3 psi increase in manifold boost compared to running the PCV system with any of the valves. Thus, Andrew’s suggestion to run a one-way check valve in series with the PCV valve is a good one.
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Old 03-13-2019, 06:05 AM
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Originally Posted by Schroedinger View Post
Thus, Andrew’s suggestion to run a one-way check valve in series with the PCV valve is a good one.
Or eliminating the failure point entirely by not using a PCV valve.

Data point- my car has some steel wool in the VC galleries. It may not be the best material choice in hindsight but it was done years ago prior to the discussion.
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Old 03-13-2019, 06:13 PM
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Just trying to sort through all of this (brain dump):

(some background info)
Water boiling point: 212F
Gasoline initial boiling point: 102F (395F final)
E85 initial boiling point: generally 70F higher than gasoline.
Oil boiling point: around 570F

assumptions (which could all be wrong!)
1. Oil will be in droplet form (not gaseous), therefore can be removed via scrubbers, baffles, filters or gravity/centrifugal force. I don't believe
2. Water will be in its gas state and needs to be kept that way until it collects in the catch can or vents to air.
3. Gasoline has the about the same range of boiling points as water and thus should follow suit.

My recent VTA catch can contents were milkshake like and reeked of gas. So I believe all three were present. It is winter time and I believe the cold catch can was condensing all three.

What the OEMs would want is to remove only the oil and return it to the engine. Then you'd want to redirect the gas and water back into the intake manifold.

Expensive catch cans include an electric heater or coolant piping to keep the gas and water in its gaseous state. They have a series of baffles and filters to allow the oil to either return to the engine or be collected in a seperate can.

If you want to filter out the oil, you need to either speed it up to spin it out (tornado type) or slow it way down to allow gravity to do its job. Filters, baffles or steel wool help to provide plenty of surface area to cling to. I do not believe centrifugal type strategies really would work because the gas just isn't moving that fast.

Options:
1. You keep it ALL in the engine (water, oil and gas) by scrubbing it off in the VC and cold catch can (vent to air) and then draining the fluids back into the oil pan (OEM MSM design). Bad idea.
2. You keep it OUT of the engine (water, oil and gas) by removing all internal traps/scrubbing and dumping it all in a cold catch can (vent to air), preferably something that can hold gallons of fluid....
3. You leave the scrubbers in the valve cover to remove a portion of the oil droplets, but the VC should be hot enough to prevent the water and gasoline from condensing.
then,
A. Collect all gas/water/oil in the cold catch can and vent to air.
B. Get that catch can super hot to keep the gas/water gaseous and only collect the oil. Return the oil to the engine. Do as you will with the gas/water. Note that an electric heater can achieve 212F, but coolant probably won't.


notes:
It is hard to keep your catch can cold in the summer.

Make sure you are piping your engine gasses DOWN into the catch can. Otherwise you will be condensing gas and water on the inside of the tube and returning it back to the VC. No matter what you do, you will get water/gasoline condensed onto the inside of the tube and collected in your catch can.

On turbocharged setups I made a MESS of things when vented to pre-turbo. Problem is, when you go into boost your are SUCKING hard on that catch can vent. My crappy catch can just ended up spewing into the turbo, into intercooler and even into my 4-port MAC valve. I no longer believe in anything other than vent to air with apologies to the environment.

Radium (with coolant lines) catch can is $350 and looks like the best. So I am going to build my own out of an aluminum box ($40) and some plumbing ($50).
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Old 03-14-2019, 10:32 AM
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Originally Posted by ChrisLol View Post
I seem to recall reading something about the cold side PCV port puking out oil out on sustained high-G left hand turns and that this (for some reason) was not the problem on the hot side opening. Is there any validity to this?

I've done two experiments with PCV system so far:

My 2017 setup:
Cold Side: GTX valve in OEM configuration
Hot Side: internal baffle holes opened to 1/2". -8 AN plumbing out to a catch can and then plumbing to pre-turbo piping to draw a vacuum.
Results: Blowby collected was minimal and usually just frothy nastiness that would separate into mostly water.

My 2018 setup:
Cold Side: Plugged with a PEX barbed plug.
Hot Side: Internal baffle holes opened to 1/2". -8 AN plumbing out to a catch can and can was VTA
Results: Collected almost all oil and would fill the catch can in ~15 minutes in track conditions.

Car has now been swapped to a 1.8L VVT w/11.5:1 compression and will be naturally aspirated for a couple years. Currently, I'm trying to answer the question, "What is my 2019 setup?"
My *proposed* 2019 setup with new VVT engine on E85:
Cold Side: Plugged.
Hot Side: Internal baffle hole opened to 1/2". -8AN hose to catch can. -8AN hose from can to OEM PCV valve modified to go inline with hose. -8AN hose from PCV valve to I/M in OEM location, also modified with -8AN fittings.

This is more of a modified, enlarged OEM style system that will pull from the Hot Side to avoid the oil siphoning issues from the cold side.
Thoughts?
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Old 03-14-2019, 11:04 AM
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Originally Posted by ChrisLol View Post
My *proposed* 2019 setup with new VVT engine on E85:
Cold Side: Plugged.
Hot Side: Internal baffle hole opened to 1/2". -8AN hose to catch can. -8AN hose from can to OEM PCV valve modified to go inline with hose. -8AN hose from PCV valve to I/M in OEM location, also modified with -8AN fittings.

This is more of a modified, enlarged OEM style system that will pull from the Hot Side to avoid the oil siphoning issues from the cold side.
Thoughts?
I may be missing the obvious here, but where is the clean make up air with this set up?
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Old 03-14-2019, 11:11 AM
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Originally Posted by ChrisLol View Post
My *proposed* 2019 setup with new VVT engine on E85:
Cold Side: Plugged.
Hot Side: Internal baffle hole opened to 1/2". -8AN hose to catch can. -8AN hose from can to OEM PCV valve modified to go inline with hose. -8AN hose from PCV valve to I/M in OEM location, also modified with -8AN fittings.
If you're going to eliminate the fresh air inlet, then having the PCV valve (and the line into the manifold) makes no sense. The whole point of the PCV being there is to regulate the drawing of fresh air into the engine by applying manifold vacuum.

Just eliminate the PCV and vent it to air through a separator / breather.
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Old 03-15-2019, 11:05 AM
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Originally Posted by tomrev View Post
I may be missing the obvious here, but where is the clean make up air with this set up?
Originally Posted by Joe Perez View Post
If you're going to eliminate the fresh air inlet, then having the PCV valve (and the line into the manifold) makes no sense. The whole point of the PCV being there is to regulate the drawing of fresh air into the engine by applying manifold vacuum.

Just eliminate the PCV and vent it to air through a separator / breather.
Ah yes, that's a good point. I was just trying to find a way to pull a vacuum on the crank case but the question, "where does the fresh air come from" is a good one and I hadn't thought about that. There has to be a pressure differential for the air to flow... Just pulling a vacuum isn't going to do much.

I guess I will change course and VTA the catch can again. See how that works on an N/A setup.
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Old 03-15-2019, 01:18 PM
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Just pulling a vacuum is better than allowing vented air. Old racecar drivers ran belt-driven vacuum pumps to keep a constant vacuum in the crankcase. It's better for your rings, IIRC.
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Old 03-22-2019, 11:30 AM
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This is a pretty darn comprehensive report on the subject of PCV catch can design. Nerds go get your glasses and a cup of coffee. You won't want to miss this.

PCV line oil removal 102

(a tiny bit more info, but most of it is repeated in 102)
PCV line oil removal 101

JOE: You should put these links up at the top in your intro.

Last edited by Mudflap; 03-22-2019 at 01:24 PM.
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Old 03-25-2019, 07:58 PM
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We will see how this setup works in a few weeks.
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