Well, it has been a while since I last posted. I have a question regarding the routing of an oil catch can's plumbing in my 1.6 Miata. I have the catch can installed in place, but the plumbing is the area in question. Could I run 2 hoses from the engine (PCV valve and intake port on the driver's side) to a "T" shaped connector to a hose that then runs into the catch can and then run a single hose from the outlet on the catch can back to the intake crosstube? I have 2 friends that are well established in the Miata business and they both have differing opinions on this matter. Also, running a hose from the PCV valve on the valve cover...would that require a plug to be put in the intake manifold to preserve the vacumm in the intake track. Enlighten me, folks!
I dunno about Miatas, but I plumbed in 2 PCV valves on my RN Truck with a catch can so that the catch can will drain back to the valve cover top.
I have the plumbing of the catch can running from the port on the driver's side of the valve cover to the catch can with an outlet hose running to the port to the intake crosstube right now. Intake manifold and valve cover are still connected via PCV valve and short hose.
Well, if you want the catch can plumbed in so that it will, ahh, catch oil, then it needs to go: valve cover to PCV Valve to one port of catch can, other port (suction) of catch can to the intake manifold. Then your catch can will "catch" the oil mist and not dump the oil into the intake. Is that what you're trying to do?
Looking to keep the blow-by vapors out of the intake tract, correct.
The vapors you don't worry about. It's the oil you want to keep out of the intake tract. If you wanted to keep the vapors out, just add a breather to the valve cover and plug everything else up. That's how 60's cars were done. A catch can, properly plumbed in, will separate the oil out, which you drain periodically, but let the vapors, which are combustible, flow on to the intake tract, saving the environment from evil unburned hydrocarbons and keeping hippies happy everywhere.
Ok. I think I got what you are saying. Can plumbs into PCV side of valve cover as well as the intake manifold. The other port of the valve cover can just have a breather slapped on and a small cap can be placed on the intake crosstube.
I will wait until I can be advised from Miata enthusiasts before making any decisions. Want to have the can plumbed correctly. The way I have it plumbed now is the way a buddy of mine that races SM and PT told me how it should be hooked up. Want the oil to stay ouy of the intake tract as well as blow by gases
Miata isnt turbo. Having blow by gases in the intake and I want to eliminate that. Miata is DD and autoX'd. Being built for track use.
A non-turbo Miata having blow-by issues?
Sounds like maybe the catch can shouldn't be your priority at this point. 
Dr. Hess wrote:
A catch can, properly plumbed in, will separate the oil out, which you drain periodically, but let the vapors, which are combustible, flow on to the intake tract, saving the environment from evil unburned hydrocarbons and keeping hippies happy everywhere.
Also helps extend the life of your engine oil since it doesn't have to absorb all that crap.
Anything goes with catch can plumbing as long as you follow two simple rules:
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The ports on the crankcase and the ports on the intake should be separated by the catch can. If you create any path between the two that doesn't go through the can, you're back to a stock setup.
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Don't leave ports open to the outside world, unless you're trying to create a VTA setup, which requires you to plug all the stuff on the intake, and isn't much better than the '60s configuration.
Edit: 3rd rule for boosted setups: There should be check valves between ports connected to the intake and the catch can so that you don't pressurize it.
Swank Force One wrote:
A non-turbo Miata having blow-by issues?
Sounds like maybe the catch can shouldn't be your priority at this point.
I cant think of any other ways I could be having oil loss. Noleaks of any sort are able to be seen. Front and rear main seals, cam seals, and CAS o-ring have been replaced in the past 8 months with OEM seals from Mazdaspeed. No white smoke coming from exhaust to indicate any oil burning from bad piston rings either.
Catch can doesnt have a breather element on it as well, for reference. Solid can with 2 ports
Got it. All is solved. Took another look at the engine and I got it.
PCV valve getsna hose to one port of the catch can while the intake manifold gets a hose to the other port of the catch can. The hose running from the valve cover to the crosstube remains or can be swapped for a silicone tube like I did.
Is the can empty? Stuff some steel wool in there to act as a filter element. Otherwise you could continue to suck oil into the intake.
Stainless Steel wool, Ross. Or stainless steel brillo pads. Don't use regular steel wool.
Yes, sorry, missed that step. I used a S.S. pan scrubber thingy.
Also even though that stuff is stainless it seems to cause many other metals to rust once they touch...just a heads up.
