|
Put the PCV back in....
So the BEGI intake manifold didnt have a spot for a pcv valve so I have been running it with a breather on both sides of the valve cover. I found that by doing this I am leaking oil from the cam cover and have also seen lower oil pressure as well. This to me is unaccpetable so I decided to drill and tap a hole for the PCV valve. I also decided to run a T fitting off that same port so that the valve cover vent on the driver side is also incorporated into the flow. This should provide better oil vapor evacuation. I got it all back on but realized that I have a leak at my throttle body because the threads in the BEGI manifold for the TB got all effed up somehow. I didnt feel like messing with it anymore today but I will be running helicoils in there when I get the chance. Ill let you guys know the results when I get it all done.
I didnt honestly think missing a PCV would matter but I think it really makes a large difference. Turbo cars see a lot of blowby so we need to have a PCV in the system to catch it all. |
I'm very anti PCV system within a turbo system. Where it would normally be open and breathing on a NA car... it'll be close on a turbo car.
Its something many honda people overlook and get increased crank pressure and have problems from that. Picture this... PCV system closes under boost... blowby and crank movement build pressure inside the motor... where does it go? Last time my lines got clogged (frozen stuff in lines to small)... my turbo became my PVC valve. I turned into Spy Hunter with the smoke screen upgrade. Open PCV system for me... or ideally... slashcut or vacuum pumped. |
Originally Posted by Splitime
(Post 86897)
I'm very anti PCV system within a turbo system. Where it would normally be open and breathing on a NA car... it'll be close on a turbo car.
Its something many honda people overlook and get increased crank pressure and have problems from that. Picture this... PCV system closes under boost... blowby and crank movement build pressure inside the motor... where does it go? Last time my lines got clogged (frozen stuff in lines to small)... my turbo became my PVC valve. I turned into Spy Hunter with the smoke screen upgrade. Open PCV system for me... or ideally... slashcut or vacuum pumped. |
Originally Posted by AndyFloyd
(Post 86899)
I use a 323gtx pcv valve so it does its job.
|
well you get the vacuum draw as soon as you let off the gas, right?
by the way, there's a PCV that goes to the intake manifold from the pax side and then the hose on the driver's side that goes to the intake tube. what is the latter and why do they go different places? |
Originally Posted by y8s
(Post 86907)
well you get the vacuum draw as soon as you let off the gas, right?
by the way, there's a PCV that goes to the intake manifold from the pax side and then the hose on the driver's side that goes to the intake tube. what is the latter and why do they go different places? Right the hose that would normally go to the intake tube has not been used on my car for 3 1/2 years. My intake tube is all sillicon so i just teed off the PCV port that I drilled. It should be better than just using a breather filter on the end of it. |
Originally Posted by y8s
(Post 86907)
well you get the vacuum draw as soon as you let off the gas, right?
by the way, there's a PCV that goes to the intake manifold from the pax side and then the hose on the driver's side that goes to the intake tube. what is the latter and why do they go different places? |
damn it...and I was getting ready to get rid of my PCV valve lol. I guess I'll be leaving it in there for awhile
|
Originally Posted by olderguy
(Post 86909)
The one on the driver's side pulls fumes when you don't have vacuum on the PCV side.
|
Originally Posted by y8s
(Post 86943)
OK so then what is the one on the passenger's side for? just closer to the combustion chamber to prevent nasty oil in the intake?
|
See, Andy? Scott and I haven't been blowin' smoke all these years after all, huh? :D
|
Originally Posted by y8s
(Post 86943)
OK so then what is the one on the passenger's side for? just closer to the combustion chamber to prevent nasty oil in the intake?
When the engine load is low (the majority of the time) pressure in the intake is also very low (below atmospheric). Crankcase fumes are pulled through the PCV into the intake, and fresh air enters into the crankcase through the drivers side vent. The valve is needed because it forces a one-way flow of gases through the crankcase during low-load engine operation. Without a one-way valve, moisture and acids from combustion will accumulate in the engine. |
No, "fresh air" would never enter the driver's side vent, as it is intended to be connected to a source of constant vacuum (you can see this on any stock car, including the Miata).
Why would you want said "fresh air" to enter the crankcase anyway? You want to pull a vacuum in the crankcase, hence the term Positive Crankcase Ventilation...we're trying to vent/get rid of the positive crankcase pressure, as it's not good for anything. |
he said it flows through... the point of the pcv is to remove pressure and, I believe, corrosive gases from the revaporization of condensation during cold startup.
I guess the flow doesn't matter as long as it's mostly OUT and never net IN. Matt |
The driver side vent is connected to vacuum? How so? On an AFM car, I guess the crossover tube may be a few kPa lower than atomospheric, but nothing close to a vacuum. On a MAF car, I doubt you could even measure it.
You need fresh air in the crankcase to replace the fumes you are removing via the PCV. Wikipedia to the rescue: http://en.wikipedia.org/wiki/PCV_valve |
I used to have problems with filters melting above the turbo manifold, so I ran a fuel hose from the driver's side PCV outlet to the other side (where the shock brace is mounted) and put a cylindrical filter there near the shock tower brace mounting point.
|
Originally Posted by mschlang
(Post 87054)
The driver side vent is connected to vacuum? How so? On an AFM car, I guess the crossover tube may be a few kPa lower than atomospheric, but nothing close to a vacuum. On a MAF car, I doubt you could even measure it.
Why would you want to re-introduce "fresh air"/pressure back into the system from which you're trying to remove pressure? |
Originally Posted by mschlang
(Post 87054)
The driver side vent is connected to vacuum? How so? On an AFM car, I guess the crossover tube may be a few kPa lower than atomospheric, but nothing close to a vacuum. On a MAF car, I doubt you could even measure it.
The whole point of the valve is to relieve pressure form the crankcase. You'll never "add" fresh air in. The pcv closes as your throttle increases, so no air enters the through the valve...on the flip side, the breather line is under a constant source of vacuum. |
Originally Posted by mschlang
(Post 87054)
The driver side vent is connected to vacuum? How so? On an AFM car, I guess the crossover tube may be a few kPa lower than atomospheric, but nothing close to a vacuum. On a MAF car, I doubt you could even measure it.
but it's there to keep whatever small amount of gases coming OUT of the drivers side vent going back into the motor. So my problem is that I have my filter mounted directly onto my turbo. no nipple. |
I have my pass side PCV hooked up normally with the miata valve, and the drivers side has a hose that connects to my intake. It works fine. I kind of want to get a catch can hooked up, as my turbo is now getting some oil in it.
-Michael- |
Originally Posted by Braineack
(Post 87117)
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.
|
Originally Posted by y8s
(Post 87138)
So my problem is that I have my filter mounted directly onto my turbo. no nipple. |
Originally Posted by mschlang
(Post 87175)
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.
|
Originally Posted by olderguy
(Post 87190)
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.
|
Originally Posted by mschlang
(Post 87237)
Yup. Atmopsheric refers to pressure, not a destination. This prevents the gases from being released into the environment.
|
I found a few pics that show the path of air through the system:
2003 Pathfinder Interga info 1/2 way down |
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. |
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! |
Originally Posted by Braineack
(Post 87644)
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
|
Originally Posted by Braineack
(Post 87644)
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!
Originally Posted by Brian
(Post 87644)
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)?
Originally Posted by Brian
(Post 87644)
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.
|
hey i just copied and pasted from the website you provided.
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. |
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.
|
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 ;)
|
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? |
someone post the MSM pcv routing STAT
|
Originally Posted by Braineack
(Post 87799)
hey i just copied and pasted from the website you provided.
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.
|
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 |
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. |
Originally Posted by mrtonyg
(Post 94555)
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!!
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. Please guys, stop making stuff up! IE, no boost ever enters you intake path, only vacuum. I could not believe some of the postings on here by Braineack and Brian. |
Originally Posted by Braineack
(Post 94635)
I'm out to get you all.
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? |
Brian, if you tap into the pipe that's between your airflow meter and compressor inlet you will not get vacuum. The only place on gasoline engine that has full time vacuum is the area behind the throttle plate. If it's in front of the throttle body/plate you will NOT see vacuum. If you don't believe me, hook up a vacuum gauge in the different spots and see what your readings are.
Any place you have vacuum at idle, WILL have boost or positive pressure from the turbo at higher RPMs. Remember that vacuum is caused by the downward stroke of the piston and the throttle plate being partly closed. For a example, a diesel engine doesn't have vacuum because they don't have a throttle plate or butterfly. Their RPMs are controlled by the injection amount of the fuel. Braineack, it was not my intention to belittle all that you have put forth in the forums here. I have read through them and found very good information. Brian, same with you man, no disrespect meant. Tony |
Very interesting discussion and I think I understand except for the whole catch can thing.
Is the catch can there just to insure that you do not somehow get oil or oily fumes into the turbo and thus get smoke, or is there some other reason?????? I could assume that as the engine ages more blow-by will result and under the correct conditions such as PCV closed (with a little boost) but some pressure in crankcase from the blow-by, it would go directly into the turbo and intake and produce some smoke. |
Originally Posted by Braineack
(Post 94635)
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.
|
Brian = Brian
Brain = Scott ;) So, somebody 'splain this to me: if there is boost or pressure present in the pre-compressor inlet tube, how could the AFM measure airflow and, for that matter, how would a turbocharger fundamentally be able to work? While I agree that there can be a vacuum pulled just behind the throttle butterfly on a turbocharged car at low-load, small throttle openings (while there's also a vacuum in the intake manifold), how could there be vacuum there when the turbocharger is producing boost (in the intake manifold)? Finally, Tony, why would you ever want to pull air into the crankcase to create pressure? This pressure is what causes the turbo to not drain effectively, causes excessive blow-by past the piston rings and robs power. |
Originally Posted by Brian
(Post 94775)
Brian = Brian
Brain = Scott |
:p you guys are just silly
|
Originally Posted by Brian
(Post 94775)
Brian = Brian
Brain = Scott
Originally Posted by Brian
(Post 94775)
So, somebody 'splain this to me: if there is boost or pressure present in the pre-compressor inlet tube, how could the AFM measure airflow and, for that matter, how would a turbocharger fundamentally be able to work?
Originally Posted by Brian
(Post 94775)
While I agree that there can be a vacuum pulled just behind the throttle butterfly on a turbocharged car at low-load, small throttle openings (while there's also a vacuum in the intake manifold), how could there be vacuum there when the turbocharger is producing boost (in the intake manifold)?
Originally Posted by Brian
(Post 94775)
Finally, Tony, why would you ever want to pull air into the crankcase to create pressure? This pressure is what causes the turbo to not drain effectively, causes excessive blow-by past the piston rings and robs power.
|
maybe mcshlang means you wont have MUCH vacuum before the turbo. It's not 20 inches at all locations pre-turbo and certainly not more than in the intake manifold.
case in point: what if you take off your intake and run an open turbo inlet? can you just leave your vent side of your pcv within a foot of it? lets see... pressure differential is going to be such that you're always removing air from the crank case, right? |
Properly piped, you can theoretically reach atmospheric pressure only momentarily in the crankcase as the PCV closes and the venturi effect has not yet taken hold from the opposite side of the valve cover plate into the intake tract on a NA Miata.
On a turbocharged Miata, properly piped, you cannot reach atmospheric pressure in the crankcase since as boost is seen at the PCV there is already a below atmosphere condition between the AFM and turbo inlet caused by the increased flow of air into the turbo acting against the restriction of the air filter and AFM. Sorry, but FWIW, Brian and Braineack have it right. |
Okay, I probably got a couple things Mike or Tony said mixed up with one another.
Tony said, "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!!" Tony: We're using vacuum on the vent side to make sure no pressure builds up in the crankcase and robs power/hurts turbo oil drainage. Some pressure in the combustion chamber will leak by pistons and, without a PCV vent, you would witness the two, aforementioned problems. Some people get away with merely a filter on that vent, and I would say they have good piston-ring-to-wall-seals and turbos that drain easily. Others (like, ya know, every builder of every aftermarket forced induction kit you see on the market for Miatas) make provisions for running that vent to a point in front of the compressor (be it supercharger or turbocharger) that will see a modicum of vacuum-ish flow. Mike and Tony: You both seem to think there's no vacuum in front of a compressor inlet. While I'm not saying there's a full 30" of vacuum in the spot where the PCV vent would connect, there is certainly some, otherwise far more people with correctly-spliced PCV vents would be experienced smoking and blown turbo seals. I've never measured it, but it's gotta be less than one atmosphere...maybe in the ~1-15" range? |
Brian, there are two reasons for running a line from the vent or driver's side tube to the point between the compressor and the air flow meter. One is that you are using metered air that has gone through the airflow meter. And if running an airflow meter, the PCV function at idle can interrupt the proper fuel trims and cause lean running at idle.
The other and less important one is that you are using filtered air without using a second filter on the vent line since it has gone past your main air filter. Trust me, or better yet measure the vacuum at the different points and you will see. The only thing you will measure in front of the compressor is atmospheric pressure. Brian said "Tony: We're using vacuum on the vent side to make sure no pressure builds up in the crankcase and robs power/hurts turbo oil drainage." Well, yes of course, that's the job of the PCV valve. At idle the PCV valve sucks fumes in to the intake manifold to burn in the combustion chamber. That's your source of vacuum in the crankcase. Anyways, I don't want to beat this thing further into the ground. Thank you all very much for being very civil...I like this board! Tony |
Brian, where in Florida do you live?
Tony |
Originally Posted by mrtonyg
(Post 94868)
Trust me, or better yet measure the vacuum at the different points and you will see.
The only thing you will measure in front of the compressor is atmospheric pressure. Am I misunderstanding something obvious? |
"Im confused by the vacuum at different points part. where on the intake manifold are you going to see any vacuum under boost?"
Nowhere, you don't see vacuum under boost. You only see vacuum at idle and part throttle because that's when the throttle plates are closed or causing a restriction. Boost pressure replaces manifold vacuum under wide-open throttle (WOT) in a force induction engine. If it's a normally aspirated engine then you would have zero to very little vacuum at WOT. Tony |
Originally Posted by mrtonyg
(Post 94868)
The only thing you will measure in front of the compressor is atmospheric pressure. Tony |
Originally Posted by mrtonyg
(Post 94868)
Well, yes of course, that's the job of the PCV valve. At idle the PCV valve sucks fumes in to the intake manifold to burn in the combustion chamber. That's your source of vacuum in the crankcase. Anyways, I don't want to beat this thing further into the ground. let's beat it more. the pcv valve is open at idle, since there is 20 ~hg. of vacuum in the intake manifold. throw boost into the equation, the pcv fully closes and seals off the crankcase from that side, preventing boost from entering or vacuum escaping. so we have the "breather" on the other side. Allowing a passage of air in/out of the crankcase while the engine is at or above atmospheric. if the breather is left open to no source, what happens? nothing, there is no boost/vaccum in the crackcase. hook that same breather line to your turbo intake, and you will pull air from both your intake filter and crankcase line. this will create a small instance of vacuum in the crankcase, helping seal rings and pull the oil of the the turbo drain line. And yes, all at the same time keep all your air metered. |
Originally Posted by mrtonyg
(Post 94881)
"Im confused by the vacuum at different points part. where on the intake manifold are you going to see any vacuum under boost?"
Nowhere, you don't see vacuum under boost. You only see vacuum at idle and part throttle because that's when the throttle plates are closed or causing a restriction. Boost pressure replaces manifold vacuum under wide-open throttle (WOT) in a force induction engine. If it's a normally aspirated engine then you would have zero to very little vacuum at WOT. Tony highs flow to lows, crankcase flows into the intake (between afm/turbo) under boost and into the intake manifold at idle... sounds right to me. |
I'm glad someone sees the light :D
|
If you have such a low pressure in front of the compressor housing as to actually contribute to evacuate the crankcase in the way of producing a vacuum, you have some seriously restrictive air filter.
Think about that. Tony |
braineack is correct
|
| All times are GMT -4. The time now is 06:58 PM. |
© 2024 MH Sub I, LLC dba Internet Brands