Put the PCV back in.... - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-27-2007, 01:30 PM   #21
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Quote:
Originally Posted by Braineack View Post
Really you dont think 20 ~hg. of vacuum is a lot? The only time your reach 0~hg. of vacuum on the crossover is under load at close to WOT.
The ONLY place you will ever see vacuum on an engine is downstream (after) the throttle. Since the crossover tube is upstream of the TB, it will NEVER see vacuum. Therefore the drivers vent is always at/near atmospheric.
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Old 02-27-2007, 01:52 PM   #22
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Originally Posted by y8s View Post

So my problem is that I have my filter mounted directly onto my turbo.

no nipple.
Same as I. K&N right on the turbo, and a small filter on the VC. Eventually I will plumb the filter in a new location, and add a nipple for the vent line.
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Old 02-27-2007, 01:54 PM   #23
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Quote:
Originally Posted by mschlang View Post
The ONLY place you will ever see vacuum on an engine is downstream (after) the throttle. Since the crossover tube is upstream of the TB, it will NEVER see vacuum. Therefore the drivers vent is always at/near atmospheric.
But if there is enough air traveling through the intake to support the intake manifold getting up to -0-, any gasses coming out of the driver side hole will travel with them into the intake manifold.
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Old 02-27-2007, 02:44 PM   #24
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Originally Posted by olderguy View Post
But if there is enough air traveling through the intake to support the intake manifold getting up to -0-, any gasses coming out of the driver side hole will travel with them into the intake manifold.
Yup. Atmopsheric refers to pressure, not a destination. This prevents the gases from being released into the environment.
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Old 02-27-2007, 03:28 PM   #25
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Originally Posted by mschlang View Post
Yup. Atmopsheric refers to pressure, not a destination. This prevents the gases from being released into the environment.
It all started with environmentalists, not because the car companies wanted to improve the auto. My first many cars just had a big pipe open to atmosphere hanging down to vent the crankcase. When you got a lot of smoke and noise from that one, it was time to do a ring and valve job.:gay:
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Old 02-28-2007, 10:37 AM   #26
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I found a few pics that show the path of air through the system:

2003 Pathfinder

Interga info 1/2 way down
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Old 02-28-2007, 10:56 AM   #27
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Hmmm, so 'splain this to me:

If the driver's side vent is actually a fresh-air intake, then why is it that connecting it to vacuum cures people's turbo oil drainage problems (that is to say, folks that otherwise are venting that driver's side to atmosphere or even mistakenly to a charge pipe)?

If anything, connecting it to a charge pipe would GREATLY increase the fresh air to it, but you'd be blowing your head gasket in the process

I stand by the fact that PCV stands for positive crankcase ventilation, and part of the system's job is to rid the crankcase of excess pressure caused by blow-by.
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Old 02-28-2007, 11:19 AM   #28
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The honda crankcase breather is a POSITIVE pressure ventilation system.The air from the intake blows into the valve cover. It is NOT a negative pressure ventilation system...it does NOT suck air from the valvecover to the intake.

so it does happen in other cars, but not on our miatas!
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Old 02-28-2007, 11:30 AM   #29
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Quote:
Originally Posted by Braineack View Post
The honda crankcase breather is a POSITIVE pressure ventilation system.The air from the intake blows into the valve cover. It is NOT a negative pressure ventilation system...it does NOT suck air from the valvecover to the intake
It does both actually. Mostly vacuum oriented though. Here's more info on the Honda stuff... http://www.honda-tech.com/zerothread?id=1199935
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Old 02-28-2007, 03:43 PM   #30
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Quote:
Originally Posted by Braineack View Post
The honda crankcase breather is a POSITIVE pressure ventilation system.The air from the intake blows into the valve cover. It is NOT a negative pressure ventilation system...it does NOT suck air from the valvecover to the intake.

so it does happen in other cars, but not on our miatas!
In post 18 I explain how the system works, sometimes relieveing air into the maifold through the vent, sometimes through the PCV, depending on engine load (manifold pressure). The miata system is identical in function to the honda's, only the placement of the valve is different. The function of the valve is the same.

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Originally Posted by Brian View Post
If the driver's side vent is actually a fresh-air intake, then why is it that connecting it to vacuum cures people's turbo oil drainage problems (that is to say, folks that otherwise are venting that driver's side to atmosphere or even mistakenly to a charge pipe)?
Not sure. I've actually wondered about that before. If you think about it, connecting it to vacuum is similar to connecting it to the charge pipe. Under boost, there is no "vacuum", so in reality they are pressurizing the crankcase any time they are boosted.

Quote:
Originally Posted by Brian View Post
I stand by the fact that PCV stands for positive crankcase ventilation, and part of the system's job is to rid the crankcase of excess pressure caused by blow-by.
I'm not sure who doesn't support that idea. All I would add is that an additional job is to clear the crankcase of sludge-forming byproducts (water, acids) from combustion blowby.
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Old 02-28-2007, 03:47 PM   #31
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hey i just copied and pasted from the website you provided.

Quote:
Originally Posted by the website you provided
All you have to learn is how the fresh air cicuit flows (follow the open white arrow) and how the crankcase vapor (with oil vapors in it ) circuit flows (follow the black arrows). Notice which circuit flows to the valve cover (on top of the engine on the left)....it's NOT the crankcase vapors. When you add a breather, you remove the line from the intake to the valve cover.


The honda crankcase breather is a POSITIVE pressure ventilation system.The air from the intake blows into the valve cover. It is NOT a negative pressure ventilation system...it does NOT suck air from the valvecover to the intake.

Breathers remove the source of positive ventilation that repressurizes the POSTIVE CRANKCASE VENTILATION (PCV) valve.

There is less pressure in the crank when you add a breather at the valve cover. The consequence of this is you get more positive blow-by from the combustion chamber past the piston rings and into the crankcase. More blow-by means less cylinder pressure...less cylinder pressure means the burn is slower and less complete...the result is more emissions and less power.

If you want to do this right and remove oil vapor from the circulating crankcase before it goes into the intake valve then, get an oilcatch can and put a breather on the catch can. Then place the catch can in between the valve cover breather and the PCV valve.

Disconnecting the breather tube, which blows fresh intake air into the valve cover, and placing a breather on the valve cover just creates more blow-by and emissions. Eventually you have so much blow-by, you lose power.
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Old 02-28-2007, 03:54 PM   #32
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the weird thing is, when my car is idling, and i blow into the breather line, large amounts of white/blue smoke shoot form the tailpipes.
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Old 02-28-2007, 03:58 PM   #33
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No, that's not weird...that just means that you and I are right, and we may continue to scoff at those who don't heed our warnings about correct PCV routing
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Old 02-28-2007, 04:10 PM   #34
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I'd like to know who you quoted from that thread. The information is only realistic in a 100% stock configuration.

Many many people in the honda camp don't understand the PCV system... its designed for NA cars... not turbo.
(this goes for many of the people asking questions and not understanding the information provided in that tread... not to mention the typical ricer honda)
They can't apply their stock NA, honda designed PCV knowledge.... so yeah... who was that post from?

Last edited by Splitime; 02-28-2007 at 04:31 PM.
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Old 02-28-2007, 04:15 PM   #35
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someone post the MSM pcv routing STAT
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Old 02-28-2007, 04:43 PM   #36
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Quote:
Originally Posted by Braineack View Post
hey i just copied and pasted from the website you provided.
Yeah, I was referencing the diagram, not the poster's opinion.

Quote:
Originally Posted by honda dood
There is less pressure in the crank when you add a breather at the valve cover. The consequence of this is you get more positive blow-by from the combustion chamber past the piston rings and into the crankcase. More blow-by means less cylinder pressure...less cylinder pressure means the burn is slower and less complete...the result is more emissions and less power.
He thinks that lowering the pressure in the crankcase is going to create blow-by. Umm, yeah.
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Old 03-21-2007, 01:49 AM   #37
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Default Pcv?!!

Sorry to bring out an old thead, but Holy Cow!!...I could not believe some of the postings on here by Braineack and Brian.

A PCV system is a PCV system...they pull in fresh air from one side (driver's side) and use vacuum (PCV side) to "burn" the fumes during the combustion process.

Braineack, if you are indeed using vacuum on the vent side, what do you think happens under boost? You would be pressurizing your crankcase...not the way to make power!!

Please guys, stop making stuff up!



Tony

Last edited by mrtonyg; 03-21-2007 at 02:01 AM. Reason: clarify
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Old 03-21-2007, 12:58 PM   #38
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Tony, sorry to be the bearer of bad news, but: you're wrong.

A little something to chew on: if the driver's side vent (notice it's called a "vent" not an "inlet") were connected to a charge pipe, then, yes, you'd see boost in the crankcase, which is precisely what you want to avoid. With that "vent" connected to a constant source of vacuum, say, in a pipe that's post-AFM but pre-compressor inlet, it'll always see vacuum...unless your turbo's furbar'd.
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Old 03-21-2007, 01:26 PM   #39
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Quote:
Originally Posted by mrtonyg View Post
Braineack, if you are indeed using vacuum on the vent side, what do you think happens under boost? You would be pressurizing your crankcase...not the way to make power!!
Abosolutely nothing. unless somehow my compressor is spinning counter-clockwise and blowing boost out the intake and pulling air from the exhaust

seriously dude, idle you car and blow into the breather line. watch you dump blue smoke out the tailpipe. now connect that smae port to constant vacuum......maybe it might, i dunno, pull the oil out of the turbo? why? oh i dunno, since the bottom of the oil drain is connected to the oil pan, which intern means that vacuum pulling out of the crankcase breather line will effect the oil drain.

Quote:
Please guys, stop making stuff up!
especially since everytime anyone was having oil drainage issues and we've ever recommended pulling the little breather filter and plumbing it into the intake has happily thanked us.....

IE, no boost ever enters you intake path, only vacuum.

Quote:
I could not believe some of the postings on here by Braineack and Brian.
and please by all means disregard my FAQ and all the help I've ever given in the past, I have no idea what I'm talking about. I'm out to get you all.
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Old 03-21-2007, 05:02 PM   #40
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Originally Posted by Braineack View Post
I'm out to get you all.
I KNEW IT!
Caught again eh!

j/k
so heres how I did mine

intake manifold|---(pcv)-|valvecover|----|intake preturbo/post afm
boosted========|====================vacuumed

thats the "correct" yes?
because the air in the crankcase has allready been metered theoretically?
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