Good to see someone using "bugger" :-)

I agree, provided that gas is sealed off during acceleration then it is only present during lift off and cruise it simply does not matter. The residue on the inside of the manifold (unlike the intercooler) could actually be positive and keep the air cool and isolated from the hot ally. I'd say that was a very minor effect though, and only on the boundary layer anyway. It is unsightly though, and dirty. But, it's also a pain in the rear to put a catch can there... so...

It would be the last thing I bothered to do.

Fred.

I put the check valve on the IM to prevent any boost from ever entering the catch can and/or crankcase. I don't see the need for any other....

gtx pcv p/n E301-13-890A
 

It's been covered before but I thought I'd add it to this thread for future convenience... GTX PCV from dealer, $16 shipped, made in JAPAN of all places, and it is indeed plastic (the housing is polymer, innards are steel, just like the non-OE crap). It holds 30+ psi with a slight leak but not "much". Shake the valve, re-test, no leak. Guess it depends on how it seats... but a check valve will make this moot.

http://i258.photobucket.com/albums/h...01-13-890A.jpg

To quote myself:
I looked around for info on injector contamination and it seems as though it's almost exclusively caused by fuel. I couldn't find anything mentioning PCV vapors contaminating injectors... anybody know anything to the contrary?

Yeah - it seems what you really want is a good PCV valve ( E301-13-890A ?) where the factory put it, and a catch can on a VTA/VT-air-cleaner and call it done. The catch can is to keep oil of of the intake, and the PCV valve should do the rest, including providing what I'd like to coin "Positive Crankcase Ventilation". Seems like a good thing. :-)

I might just pick up one of those nice valves. I'll see if I can get that on mazdacomp.

I would like to put a bigger hole on the VTA side of things. Maybe I'll pull the valve cover and enlarge it. Any point to enlarging the hole going to the manifold? I doubt it, the PCV is going to be the bigger restriction anyway.

Am I missing something here?

yeah, the VTA side is probably too small to flow what is required at high sustained load. That IS the case on the FE3 anyway. Any good pics of how the miata cam cover is?

doesn't this just take use back to putting a filter on the driver's side of the valve cover, and a gtx valve on the other side?

It sure does!

Is there a problem with that? Adding brain's check valve wouldn't hurt, but if the PCV is up to the task, then why worry about it? And, it should be up to the task, it's made for a turbo car.

The only other thing is the catch can, placed between valve cover and turbo-intake, the slight vacuum helps clean vapors out of the valve cover, and the enlarged hole certainly can't hurt.

If there's something that doesn't do, please post it! Otherwise, it's the first system, simplest system which:

1) Puts a vacuum on the crank case under moderate throttle
2) Prevents the idle from walking due to leaked air through breather
3) Precents pressurizing of crank case from manifold
4) Prevents spilling of oil into turbo intake and IC piping
5) Gives an outlet for crank case pressure under high load conditions.

I'm with abe and always have been in favour of an enhanced OEM setup. You want clean air cross flowing through the engine under moderate throttle conditions. I'd be tempted to allow a restricted feed of air from the engine to enter the manifold under heavy vac conditions and form part of the idle air supply, however due to the lower O2 content of crank case gasses that would probably result in an unstable idle under different conditions.

4. it will only do with a really good catch can
5. it will only do well enough if the hole(s) is/are big enough.

Hence, on the FE3 I would do something like what rob has on his.

• stock PCV (possibly with check valve) from RHS to intake (drivers side is which side again guys??? :-p)
• stock breather enlarged and fed to the turbo inlet via a good catch can setup that doesn't let ANY oil through.
• extra breather to exhaust venturi system or just filter via catch can.

That way you get cross flow at moderate throttle, cross flow at high throttle and solid breathing at high throttle with no/little restriction.

I know for a fact that I've got crank case pressure issues as I found oil sprayed horizontally quite far away from the hose i left hanging off the cam cover. I'd like to resolve that properly before I do much further thrashing of it.

Fred.

Ages ago, Braineack said the vacuum between filter and turbo inlet was ~1-2 inches...

So enlarged holes aside, I did some "testing" on this a few minutes agoo...

On my car, the vacuum between a brand new K&N and the turbo inlet was negligible, almost immeasurable, probably <1 inch. From this, I feel it's safe to say that adding a catchcan here, especially if it's steel-wool-impregnated, would drop that value to zip. This immeasurable vacuum will do nothing in terms of scavenging, on my car anyway.

Of course in boost the pressurized gases would get forced through... just don't count on an asspile of vacuum.

Scavenging is really only taking place on the cold side. And air will be going into the VC through the hotside vent to compensate for the draw from the PCV.

I don't expect any of this to change anyone's mind on the setup they choose.. but stock seems pretty fucking good (with a check in the PCV line).

If my vent line going to the intake shows considerable oil, I suppose a catch would be in order but I'd expect crank case pressure to rise as a result. Compromise I guess.

Correct, either it is just releasing the gas generated and keeping pressure low with flow past piston rings, through block/head and out into turbo inlet/the world OR it's drawing fresh air in through the turbo inlet and sucking dirty air into the engine.

A you want to keep the air in the engine clean and dry and keep the water and co2 that make your oil acidic out
B you want to ensure you don't get excess pressure in there during boost

B is the reason people ditch the PCV half. The double the flow out of the head during boost when the PCV would be shut. However they ruin A because of it.

BTW, the NA FE3 that I saw blow a dip stick out had no PCV and BOTH dumping to under the car through 3/4" hose... still pressurised to all hell. Hence enlargement IS necessary if you are flogging the car like a dead horse...

It's good to get this nice and clear, many thanks to Rob for instigating it. I'm appreciative of his work.

Fred.

I sure as heck wouldn't have expected a lot of vacuum on the intake. But I guess you could put a little venturi type restriction in there ahead of the turbo if you really wanted, I'm sure it would do wonders.

Mainly I dump it into the air cleaner to burn what fumes I can. Anything I can do to not beat the environment more than I need to to have my fun is good.

Really a belt driven or electric pump is the answer if you NEED to have vacuum on the crank case, most other things are a joke under real power.

I think the secret to a good catch can, like the secret to a good muffler, is dead volume, unfortunately. So lots of space, lots of twisty turns, and some stuffing. It'll be a hell of a lot better than my 3/8" hose.

so after two months of speculation who here besides m2cupcar is actually going to get around to building one soon?

nice job, but why not a can thats a bit more shinny like stainless steel? Both will work the same, but stainless steel is nicer to see.

If there is any vacuum at the turbo inlet your air inlet plumbing SUCKS badly and you are losing power. Like abe says, it's just to burn the vapours. The only reasons to not put it in there are octane dilution and oil film on the intercooler.

shouldn't there at least be lower pressure there because of the fast moving air into the compressor?

Movement alone doesn't generate pressure differences. You need a restriction for that. if you put a venturi tube in there it would create a vacuum for you though, but I'll be stuffed if I'm putting something restrictive in the way of my turbo inlet.

I'm a little late to this party, but have read everything thorougly and have two questions.

What's the difference between the manifold side and the breather side?

As far as I know, they both utilize the same baffling system into the valve cover. Why not simply plug one of the holes, and run your whole valving system off the other if #1 is the favorite consensus?
The small amounts of boost we're talking about making it's way into the crankcase can certainly be vented fast enough through just one of the openings in the valve cover, no?

Oh yah, and how the hell is everybody actually attaching a hose to the little rubber grommet where the PVC valve normally goes?

The breather side typically has a much better longer baffle chamber arrangement.

Because you lose the PCV operation and don't gain any extra flow.

I firmly believe that "boost is pressurising my crank case through the PCV" is a load of bollocks and that all the "pressurising" is being done past the rings.

I think "certainly NOT" is the consensus there. In fact I'd go so far as to say that using both of the stockers is NOT enough either.

Fred.

you contradict bernoulli.

http://upload.wikimedia.org/math/8/2...4787380f8a.png


v = velocity, p = pressure. as velocity goes up, pressure goes down.

so you can have pressure drop in the intake without a restriction.

plus there will be a pressure gradient at the turbo inlet as you get closer to the compressor wheel. remember it is not the turbo that sucks air in, it's the ambient pressure that pushes it into the turbo because of the low pressure region at the inlet.

You fail reading comprehension.

If velocity stays the same pressure stays the same. Movement alone (without change on rate of movement etc) does not generate pressure differences.

Your equation is only valid away from any walls of say an intake tube and also only to incompressible fluids. The air in your intake satisfies neither of those requirements.

You are right that there will be a pressure gradient leading into the compressor, however its contour would be something like the inverse square. If you applied a still body of air to that vacuum source you might be able to detect it. With a steady state equilibrium reached where the speed of the air moving in and the pressure differential across it (it's invalid to say that it is sucked in just the same as it is invalid to say that it is pushed in) that makes it move are matched then the pressure drop relative to the outside ambient air should be so close to zero that you'd have a hard time measuring it. If it's not, your intake sucks.

End rant :-)

Fred.

It may be impractical and unnecessary, but would it be feasible to monitor crank case pressure by tapping the VC for a vacuum line which would go to a second MAP sensor, like the one for barocor?

Your log would show exactly what pressures you're dealing with, possibly producing evidence which would determine if OE vent size and baffles are adequate

Indeed it would be feasible and not too hard. Just hook a map sensor to a spare ADC input and log the values. You can do the conversion to pressure afterwards easily. I'm interested to see what you find out, but you have to thrash the crap out of the car to do a good test on this.

bernoulli applies for both compressible fluids and boundaries.

and last time i checked, the ambient air outside my intake pipe is not moving and the air inside it IS moving.

I bet my intake tube flows better than any miata with a filter on this site. :bigtu:

I could get "moving" air between 10 psig and 11 psig, and have higher pressure. :-P

More to the heart of this conversation, you're not going to get *significantly* low pressure in the intake unless the system really is restrictive. A bad air cleaner might do a bit. Certainly an OEM intake has a significant pressure drop, though still not large.

Anyway, what I'm taking from all this is the OEM system is a good thing to shoot for, an upgraded PCV and catch can are what the descerning turbo enthusiast will be putting on his miata this season.

Mine are on order, and will be installed with catch can directly.

ok fine, BRAINEACK, can you bring your magnehelic over and put it in my intake behind the filter??

http://gallery.y8s.com/d/17058-2/DSC02751.JPG

Um, bends are bad fer flow, m'kay?

Not only is your filter half the size of mine (flow area wise) your intake tube is also less than half at the intake end! ;-) (It's the same at the turbo though) Mine also has a "velocity stack" leading from the 6" into the 4" <<< (quotes required for Dr Evil style pronunciation)

I'm sorry for being less of a man than you y8s ;-) I'll just have to take consolation in the fact that I'm less of a man while not driving a Miata :-)

Fred. (living dangerously)

"Living" he says. In England. Oxymoron.

my velocity stack is built into the turbo. if I ran a different compressor housing, i'd be all over a velocity stack, but I'd probably put it in front of a filter to avoid obstructing the opening of the stack.

honestly, with a filter on there mucking it all up, it probably is sub optimal anyway.

yes i could. it's in my trunk.

Let's be honest here, if there was a measurable pressure difference between your setup and mine at the same RWHP I would be extremely surprised.

All bullshit aside, a lot of the stuff we all do to our cars make so little difference that it just doesn't matter. Even when you assemble them all together the increase in HP isn't that much. The key thing is to not do anything badly :-)

I'm going to summarise all of Rob's PCV threads into an article at some point when I have more time. I'll link it here when I do.

Fred.

A lot of times I'm willing to do the legwork myself, experiment, and do a writeup on my findings... but would somebody just make a drawing and tell me what to do. Whadda I hafta build to get the best of all worlds here?

Please spell it out and use small words.

I believe the drawing below illustrates the general consensus on a crank case vent system adequate to manage boost blow by and still remain somewhat eco-friendly.

www.autoshop101.com/forms/h63.pdf

Toyota and Braineack seem to disagree on PCV valve operation. I'm with Toyota on this and claim you shouldn't/don't need the check valve. I'll stick with that opinion until someone proves that their crank case is being pressurised by boost through a pcv sized hole when the exit hole is equally sized or larger. (note, not physically possible :-p)

You do the loveliest diagrams Rob! I'd note that the "breather" location needs to flow well and that the main issue seems to be that it doesn't and the crank case get's pressurised.

Fred.

pvc catch can
 

And here's a diagram for a cheap catch can. This fixes some stuff wrong with mine. I don't have the pipe nipples penetrating into the can nor the divider, so some of the oil vapor actually makes it out of the filter I have stuck on the end (no it doesn't go to the turbo intake...yet). So that means if it did run to the intake, I'd have vapor condensing in the hose and possibly making it to the compressor. The divider wall and pipe nipples should for the vapor deeper into the can and provide more surfaces/opportunity for condensation. I prefer the divider over packing.
http://i158.photobucket.com/albums/t...vccatchcan.jpg

Leave the internet. Go idle your car with a hose directly from the IM to the valve cover.

I'll be here waiting for your "discovery"



REALLY???!?!

No discovery required. The throttle plates in stock config pass almost no air at all. The PWM idle control corrects idle level based on what the rpm actually is. Thus, if it's getting some air from the crank case it's going to close the PWM valve to match. Likewise, if it's getting some O2 free gas from there it's going to feed in sufficient air to keep the idle up. Given the diameter of the PCV orifices and the engines idle air requirement, I doubt you could keep it alive based only on the PCV "leak".

Too slow with the edit there... or too fast.

Yes really. You stated that it is CLOSED at high vacuum. It is not closed, merely restricted. Restriced != Closed.

Smile, it'll do ya good :-)

oh give me a break, go suck on a pcv.


I was mearly letting Abe become aware of his potential unrestricted "leak" based on his drawing.

I'd be curious to know the exact differences between the stock miata valve and the gtx, and why the stock unit is built the same. What compromise is made with the gtx valve being more resistant to boost?

I know with the Advance Auto ones I've bought, the plunger simply didn't seat well. I could blow through it with my mouth. That's about 2psi. With an air compressor hooked up at 15psi, sometimes it would seal, sometimes it would leak fairly heavy. I bought (what i think is the GTX one) from Rosenthal and it would always seal and has yet to fail on me. I had one from advance fail to operate at all within a few hundred miles.

So for those of us who are less concerned with being eco friendly, whats the easiest/most simple setup? Currently I have a gutted pcv with a filter and capped the breather side. The car runs just fine. The only issue I have is I get some oil coming out from the pcv side with the filter which I plan to make a catch can for.
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like i've stated before: pcv and breather line into a catch can with a huge atmospheric port.

Attachment 212040

Sure thing! :

http://www.youtube.com/watch?v=mhbZBefwbtQ (not finished loading at the time of posting, but couldn't be bothered waiting anymore)

Sealed perfectly at ~2psi and held vacuum very well in the opposite direction, however flowed nicely with vacuum applied from the intake side :-p

Just as it should be, boost or no boost. Stop buying CHEAP JUNK PIECE OF SHIT RIP OFF COPY CHINESE MADE USELESS PCVs from your local retail outlet and stick genuine Mazda parts in there. For stuff that matters there is no substitute (cept possibly nissan or toyota parts instead)! Ditto radiator caps, ditto thermostats.

Article is 3/4 done, I'll post a link later or tomorrow when I'm happy with it and have moved it to a public location.

Fred.

Sorry man, but the pic is just way gay.
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Fred, stop being a condescending jerk.

Mazda OEM PCV valves for the miata are what most people buy. The OEM GTX valve is what everyone buys after the Miata-specific ones fail.

Exactly what was the failure mode, and where is the tell tale that it was the PCV failing? Link please ;-)

being black flagged on the track.....that was my tell tale sign.


now throw a handy vac on the IM side pulling about -10psi :)

The plunger side of the valve fails and the plastic housing itself comes apart... pics are not for the weak of heart:
https://www.miataturbo.net/forum/showthread.php?t=9920

I'm not sure I like the VTA in the catch can. Technically, it shouldn't hurt anything, but again, there's no reason to not collect that stuff. Compared to the 50/50 by volume gasoline you're spraying in, you won't make any real difference to how the motor runs. If you were burning much of it, the OEM wouldn't pass smog with a system like PCV in. :-)

Im pretty sure the green "breather" is far and away the BIGGEST restriction in the entire system, pluming the catch can to the turbo inlet is fine and not going to be the limiting factor.

Also, doing it as shown will want a filter on the VTA since you're going to suck some into your motor through there. Well, not likely, but in theory. The other way, everything's already a closed system.

Fred, you should go as PCV testing guy for halloween. I noticed sucking on my own PCV that with a little touch on the back of the punger, it would seal in the other direction. Call it 5 psi?

Good lord, did I not get the right PCV valve? I ordered the part number from the picture of the PCV valve showed earlier in this thread, and it came and was plastic. I just figured, well, the GTX one was plastic...

I've never seen one "GTX" look the same....and this is from mazda....ill have to look at mine again. I just know i have a factory valve, and it's fine.

LOL, nice work. Still, the part where it is bonded together is still intact. Plastic mouldings (like pistons) don't just snap in half by themselves and boost applied from the end axially simply would not have the required force to exceed the yield strength of the part in that fashion. I'd place a small wager that you or a mate leaned on it inadvertently at some point. Most plastic radiator tanks die that same way too. How many others have had this exact failure?

For y8s :

I rest my "buy OEM" case!

Brain, pissing oil into the intake doesn't say "failed PCV" to me, it could have been, but it could have been other things too. Which of the two possible ways was it heading into your engine?

Fred.

where'd you even quote that from? samnavy used his stock valve and it died.

^He's saying that particular kind of failure isn't possible and that I probably leaned on it at one time or another with my hand and cracked it... which I can't dispute. All I do know is that my stock OEM naturally aspirated Miata PCV valve broke and almost cost me an engine... and my Advance autoparts Mazda 323GTX Bosch part is still going strong. My case is not unique as a search will reveal.

FWIW, the Miata and 323 part numbers are different for all manufacturers... not just the OEM Mazda one.

Sometime this week I'll hit HomeDepot and get the parts for an M2cupcar designed catch-can and route it in the manner detailed above. I'll let everbody know how it works out.

I've been wanting to do this for a long time and this thread is just the impetus I need.

I wanna falcon punch someone....

Try page 2 ;-)

Sam, do you agree? It looks like it was cracked by sideways pressure. I myself have wiggled them sideways with great force to get them out on occasion, it could exactly that behaviour which broke it. Or perhaps the lean thing. What do you think?

When I prompted for that I was 50/50 expecting someone to post pics of the bonding coming loose and it literally falling in half. If that happens, to Mazda units, made in Japan, not NA, then I'll bite my tongue a little more. But, I strongly doubt it. The GTX isn't the only boosted car out of japan, they all have PCVs on them, all are SO similar in design and construction. And unless they are faulty or dirty they will all hold backwards pressure to some extent just fine.

Fred.

I haven't used a GTX valve yet. But I can say that every OE stock Miata valve I've tried (five) leaks over 10psi. Under that they are fine. I've had one autozone cheapy that wouldn't hold back more than a couple of psi. I had another noname for a supra that worked for about 500 miles and the started leak over 10psi.

Abe- that hose at the bottom is a drain, not VTA. The vent line is what runs to the intake. I'll update the image and label that.

I remember asking you this before, but tell me again how you tested them to prove that they leaked? Perhaps Miata ones just suck? If I can find some compressed air I'll try to test this Toyota one.

I've finished the article, feel free to rip it to shreds. Literally, be as hard and critical as you like. I'm devoid of feelings to hurt anyway ;-)

http://www.diyefi.org/forum/viewtopic.php?f=24&t=357

Hopefully it goes a long way to making sure I never type about this stuff again...

Fred.

M2: Oh, ah! Ok, then yes I like it! I sortof thought it was WAY too schematic to have a hose off the bottom. :-P

So why no baffles? You don't like the steel wool since you don't want to steel wool your engine internals? I could see that. I doubt a simple baffle will some anywhere NEAR working as well.

Probably one long coiled rope/wire would be good. In high reliability applications I've seen all sorts of things makes that way. But I don' think flat surfaces are going to catch much.

Same for me, I have the can and lacked a plan. Now, with both in hand, I'm sure the outcome will be grand.