Brain has the dumb again.

The op's pcv setups are perfectly adequate for N/A cars and milde turbo setups. We really only run into problems with crank case venting in 1 case. Big power turbo cars making significant lateral grip. For cars like this we delete the pcv port on the head because if we leave it open it just dumps oil out on sustained corners. See my car or Bundy's for some of the most advanced crank case venting on the site. I no longer have a pcv valve because my car doesnt see significant time cruising, if it did I'd run one. I have a massive AN fitting on the head, with the small port in the head baffling drilled out And I tapped the block for a 1/2" NPT fitting just above the starter to run another -10 an line. Both go to my air/oil separator and into my pre-turbo intake with a slashcut. At worst the slashcut doesnt work in the intake and I still get the slight vacuum created between the turbo and the air filter. I just didnt feel like doing the exhaust slashcut at this time, and its also illegal for every raceclass above mine for some stupid reason.

You pretty much dont want to just vent both sides of the engine to air without pulling any vacuum unless you're incredibly lazy.

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fuck your vacuum. you think mazda was engineering vacuum in the crankcase when they put a restrcitor on the breather line to the intake? past the small tiny little opening for all the baffling? if anything that will create positive pressure.

go fuck your goat.

Quality Control Bot Activated.

:laugh:

If you are running long hard left hand corners without a pcv in a big hp turbo car you well be losing oil out the pcv port in the head and probably on even less hp cars as there is alot of oil on the top of the head when running high sustained revs on the track. I am running big hp with the pcv in the system then to a catch/seperator can. As mentioned above under boost the pcv should be closed. The other side goes also to a catch can with a filter for when under boost it should be the only one working. Been that way for two seasons and seems to work just fine. Also if you are running a catch can with a filter on it you shouldn't have vacuam anywhere in the system should ya?

resurrection bump to see if I can get a consensus. Obviously different people have found different solutions that work for them but I want to make sure my plan will work for DE's.

The previous owner had the pcv connected to a diy catchcan that he mounted in the passenger wheel well and the breather hose on the driver's side was about 2 inches long with a small air filter on the end. As I discovered at VIR this weekend, that setup results in oil getting sprayed out of the filter and all over the engine bay. :facepalm:

I then bought some 6AN hose and tried to tee into the pcv hose leading to the catchcan. Fail. The catch can filled up real quick (just doing pulls off track) and the exhaust will spit out a nice big oil smoke screen on full boost and off throttle.

So I now have the pcv hose back to the original catch can configuration and the passenger side is now hosed to a temporary catch can that I had to seal quite well as it still blew oil out easily. At least it doesn't smoke heavily now! :D

So should I just build a proper catchcan on the driver's side and be done with it? Or would it be better to weld the port shut and increase the driver's side connection to a 10-AN? I don't like how much oil the driver's side breather port spits out and since it doesn't do it on the street I'm guessing it is just because of cornering forces.

you need better oil control rings on your pistons...

except I get no oil in either catch can under full boost in a straight line. And I get hardly any oil in the passenger side catch-can on track

and even if my rings are in fact bad (good possibility) isn't the driver's side breather vent leaking oil a known issue on track miatas?

Search is good
 

Since searching solves everything...:party:

So clean and sealing the driver's side baffles, welding the passenger side PCV and welding in a -10AN bung to the driver's side to route to a catch can is my next project.

My setup is 1 hose from each side of the valve cover going to the can that has a filter on the top. Am I doing it wrong? The can isn't plumbed with a 3rd line for a return. It can also be a sealed can without a filter. It's not getting anything but some moisture and left-over assembly lube. Should I cut a 3rd port in the bottom of the can and lead it to my pre-turbo intake pipe?

https://www.miataturbo.net/attachmen...ine=1399920653

At the track, the engine ran really rough and filled the catch-can quickly when I had the breather vent hose tee'd into the pcv line. Like Brain said, might be due to excessive blow-by or whatever but I never had a problem with the setup (not tee'd) until I got on track

I also noticed when the car is warming up for the first few minutes, if I blip the throttle I get some kind of steam (similar to what comes out of exhaust on a cool morning) that comes out of the filter on top. I'm thinking I should take the filter off and use that third port to run to right before the turbo..

Running those two hoses to the catchcan is a simple passive system though you may want to stuff it with steel-wool to help scrub the air of nasty oil vapors before it is vented through the filter.

You DON'T want to plumb a 3rd line from the bottom of the can because then all of the acidic crap that pools at the bottom of the can would get drawn into the intake. Kinda defeats the purpose of a catch can. Replacing the filter with a hose to the intake pre-turbo would be an active system and would be more environmentally friendly but would increase the chance of detonation.

Installing baffles or some steel-wool in the catch can to stop the air from just going straight out of the filter might fix any 'steam' coming out of the filter. With how that catch can is designed, I don't see it being all that effective at catching anything

I'm not worried about appeasing the EPA but am worried that I have the wrong setup for my purposes. I do about 4000 street miles a year. The setup I have I see on track cars that likely do less.

I just want to know what side effects to expect from running the system I am and if there's anything I can do to improve it.

Venting through a catch can to the atmosphere like that will give you no side effects. That is essentially what my car has been running for the last 5+ years

You're overthinking it. That setup is fine, and certainly way better than the crap that came stock on your car.

Maybe I take people here too seriously, but then what does this mean "You pretty much dont want to just vent both sides of the engine to air without pulling any vacuum unless you're incredibly lazy."

First off, i don't know what that means, because you're venting a valve cover, not two sides of an engine. Sounds like something Leafy would say. :rofl:

They're saying that a catch can/crankcase ventilation is most effective when you have some sort of vacuum pulling on your ports.

And on paper, that's true.

In the real world, if you can deal with some of the smells you might get from venting to atmosphere and your motor is healthy, what you've done works just fine and is found on 99% of modified motors making far more power under far more boost than anyone who has posted in this thread.