Another thought about ATI's PCV valve system
08-23-2003, 07:27 PM
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Another thought about ATI's PCV valve system
I started a separate thread because the other one is not addressing MaxHax's engine woes.
I've been doing some more thinking about this ATI setup.
For those that don't have an ATI procharger or haven't looked at it closely... both engine PCV valves get routed into one T fitting that then goes to the Air filter.
It seems to me that the T fitting that the two PCV valves go into is not the best answer for venting crankcase vapors.
The reason I think this...... A PCV valve is nothing more than a one way valve that's opened by intake manifold vacuum. In our case that vacuum is being created by the impeller on our superchargers. If there is positive pressure on this valve it closes. The reason being that if your car backfires you don't want the backfire flame to be vented into your crankcase with all those flammable liquids.
Anyways, if one PCV valve gets stuck open it is going to vent more than the other PCV valve. That will create positive pressure on the PCV valve which automatically closes it. So basically you've got one fully open and the other fully closed. This causes all crankcase pressure that's supposed to go out of two separate valves to vent out the one that's stuck open which will most definitely cause the oil in your valve train to blow out of it.
Seems to me the best/safest way to vent the PCV system would be to have two separate hoses, one from each PCV valve to go to your air filter. It's a little more hassle, but in case of PCV failure it won't cause the oil to blow out because it still has two valves to vent through.
Someone give me some feedback... GaryK. I think my theory is right, but not sure.
I've been doing some more thinking about this ATI setup.
For those that don't have an ATI procharger or haven't looked at it closely... both engine PCV valves get routed into one T fitting that then goes to the Air filter.
It seems to me that the T fitting that the two PCV valves go into is not the best answer for venting crankcase vapors.
The reason I think this...... A PCV valve is nothing more than a one way valve that's opened by intake manifold vacuum. In our case that vacuum is being created by the impeller on our superchargers. If there is positive pressure on this valve it closes. The reason being that if your car backfires you don't want the backfire flame to be vented into your crankcase with all those flammable liquids.
Anyways, if one PCV valve gets stuck open it is going to vent more than the other PCV valve. That will create positive pressure on the PCV valve which automatically closes it. So basically you've got one fully open and the other fully closed. This causes all crankcase pressure that's supposed to go out of two separate valves to vent out the one that's stuck open which will most definitely cause the oil in your valve train to blow out of it.
Seems to me the best/safest way to vent the PCV system would be to have two separate hoses, one from each PCV valve to go to your air filter. It's a little more hassle, but in case of PCV failure it won't cause the oil to blow out because it still has two valves to vent through.
Someone give me some feedback... GaryK. I think my theory is right, but not sure.
08-23-2003, 07:54 PM
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WTF over?
OK, someone deleted the thread regarding MaxHax's engine issues.
Oh well, anyways, what I said in that thread was that his issues could also be too much oil in the crankcase because of improper use of the dipstick caused by the location of the SC and oh hell I don't remember now. Hopefully it wasn't important information. guess I should've started a new thread before I posted my reply to the other one. The thread was degenerating quickly anyways.
Oh well, anyways, what I said in that thread was that his issues could also be too much oil in the crankcase because of improper use of the dipstick caused by the location of the SC and oh hell I don't remember now. Hopefully it wasn't important information. guess I should've started a new thread before I posted my reply to the other one. The thread was degenerating quickly anyways.
Last edited by jesseenglish; 08-23-2003 at 07:57 PM.
08-23-2003, 10:19 PM
#4
Well, I haven't dealt with pcv systems all that much, so I'm trying to reason through this myself. I think most current pcv valves are set up to open more at higher "manifold" pressure. If one is stuck open and the other one functions normally, the good one should actually open more than it normally would because of the higher pressure created by the stuck open valve.
Also consider that running separate lines rather than a tee into one line would probably still operate the same in the end. They have to see a common pressure somewhere, and I'm not sure what the difference would be from the tee to the air filter where they would have to go if run separately.
So, I guess I don't see that an improvement could be made by running separate lines to the air filter.
Also consider that running separate lines rather than a tee into one line would probably still operate the same in the end. They have to see a common pressure somewhere, and I'm not sure what the difference would be from the tee to the air filter where they would have to go if run separately.
So, I guess I don't see that an improvement could be made by running separate lines to the air filter.
08-23-2003, 10:37 PM
#5
Ok, now I'm sitting here thinking about this, and something isn't making sense. In factory config, one pcv is hooked up to the intake plenum, and one is hooked up before the throttle body in the intake tube if I remember correctly. These two pcv valves may actually operate a little differently, but I'm just speculating. I say this because the conditions seen by each can be different. I'll try to find out....
08-24-2003, 06:03 AM
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Originally posted by GaryK
Well, I haven't dealt with pcv systems all that much, so I'm trying to reason through this myself. I think most current pcv valves are set up to open more at higher "manifold" pressure. If one is stuck open and the other one functions normally, the good one should actually open more than it normally would because of the higher pressure created by the stuck open valve.
Well, I haven't dealt with pcv systems all that much, so I'm trying to reason through this myself. I think most current pcv valves are set up to open more at higher "manifold" pressure. If one is stuck open and the other one functions normally, the good one should actually open more than it normally would because of the higher pressure created by the stuck open valve.
I'd really be interested to find out what kind of vacuum pressures that PCV valve is seeing. I'd venture to guess it's not seeing a whole lot which, depending on the vacuum ratings of those PCV valves could potentially be a problem.
Originally posted by GaryK
In factory config, one pcv is hooked up to the intake plenum, and one is hooked up before the throttle body in the intake tube if I remember correctly. These two pcv valves may actually operate a little differently, but I'm just speculating. I say this because the conditions seen by each can be different. I'll try to find out....
In factory config, one pcv is hooked up to the intake plenum, and one is hooked up before the throttle body in the intake tube if I remember correctly. These two pcv valves may actually operate a little differently, but I'm just speculating. I say this because the conditions seen by each can be different. I'll try to find out....
08-24-2003, 07:15 AM
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Oh and I talked to MaxHax to ask him if after they disconnected the PCV system and put it in the bottle if the bottle was the bottle still filling up with oil. He said yes, I don't know how much oil or if that was just oil still left in the PCV system, but that shouldn't have happened, because if the pcv valve has no vacuum on it, it should be closed.
I've also been trying to figure out why my idle is rough now that I have the Procharger on and problems with the PCV system could explain it. I was attributing it to additional load on the crankshaft pulley, but if there is not enough vacuum on the PCV valve at idle then crankcase gases won't be ventilated which will cause a crappy idle like I'm experiencing.
Maybe I'm just being a conspiracy theorist here, but I really do not like the design of this PCV system because most of the vacuum created by the impeller on the supercharger is going to be exhausted by the K&N filter before it even gets to the PCV hose.
Here's a good document on the proper operation of a PCV system. It's for a Toyota, but it's the same for all cars.
http://www.autoshop101.com/forms/h63.pdf
I've also been trying to figure out why my idle is rough now that I have the Procharger on and problems with the PCV system could explain it. I was attributing it to additional load on the crankshaft pulley, but if there is not enough vacuum on the PCV valve at idle then crankcase gases won't be ventilated which will cause a crappy idle like I'm experiencing.
Maybe I'm just being a conspiracy theorist here, but I really do not like the design of this PCV system because most of the vacuum created by the impeller on the supercharger is going to be exhausted by the K&N filter before it even gets to the PCV hose.
Here's a good document on the proper operation of a PCV system. It's for a Toyota, but it's the same for all cars.
http://www.autoshop101.com/forms/h63.pdf
Last edited by jesseenglish; 08-24-2003 at 07:23 AM.
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08-24-2003, 12:55 PM
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A PCV valve isn't neccesarily about manifold vacuum. I think it's geared more towards relieving built up pressure in the crankcase. The valve opens as the pressure rises and releases the vapor into the intake as a means of emmissions control. Back in the old days (way before my time!), they had what they call a "road draft tube" where excess crankcase pressure was released directly into the atmosphere.
I think if we were to address any issue with the PCV system in a boosted application, then we'd have to look at the manifold pressure (positive) actually preventing the valve from opening. This would be from the manifold pressure exceeding crankcase pressure. I think this is why they re-route it away from the manifold into the intake... BEFORE the compressor, where intake pressure is negative. This way we are back into a vacuum situation while crankcase is positive pressure. This would allow the PCV valve to open, thus allowing the system to operate correctly.
Dave
I think if we were to address any issue with the PCV system in a boosted application, then we'd have to look at the manifold pressure (positive) actually preventing the valve from opening. This would be from the manifold pressure exceeding crankcase pressure. I think this is why they re-route it away from the manifold into the intake... BEFORE the compressor, where intake pressure is negative. This way we are back into a vacuum situation while crankcase is positive pressure. This would allow the PCV valve to open, thus allowing the system to operate correctly.
Dave
08-24-2003, 01:29 PM
#9
These valves should depend on vacuum/pressure to some extent to meter the crankcase vapors. It seems that with the new location of the vent, the characteristics of the system are different, but are they different enough to matter? It probably will actually vent a little more than normal since there isn't as much vacuum on the vent side.
Also, if the pcv was hooked wrong, which may have happened on Max's car, then one problem would be the improper operation of the pcv system as Dave already said. But even worse than that, the pcv valves might not be able to handle boost pressure and could actually allow the crankcase to be pressurized the same as the intake plenum.
Also, if the pcv was hooked wrong, which may have happened on Max's car, then one problem would be the improper operation of the pcv system as Dave already said. But even worse than that, the pcv valves might not be able to handle boost pressure and could actually allow the crankcase to be pressurized the same as the intake plenum.
08-24-2003, 02:20 PM
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I'm not looking at Max's installation in particular, I'm talking about the design of the PCV system in general. It doesn't seem very well thought out to me. I could be wrong, maybe ATI spent the time to figure out what the vacuum pressures would be needed to properly meter the crankcase vapors, but I doubt it.
What should have happened, is they should have figured out what vacuum levels would be seen at the new location and supplied two new PCV valves along with the ATI supercharger kit that would operate properly given those levels.
No we don't really know if it's enough to effect things or not. What needs to happen is we need to figure out the specs of the stock PCV valves and see if the vacuum levels seen are enough to open them up. The way I see it is at the stock locations those PCV valves were seeing A LOT of vacuum and now I doubt they're seeing any.
Blck Mgc Rcng,
The PCV valve is designed to open when it sees a vacuum not when it sees positive crankcase pressure.
Gary,
I don't see how the installer could've hooked it up wrong unless they decided that the T wasn't needed and they hooked up the passenger side PCV valve up to the stock location. That could be a real problem because the PCV valve would never open when the engine is on boost.
What should have happened, is they should have figured out what vacuum levels would be seen at the new location and supplied two new PCV valves along with the ATI supercharger kit that would operate properly given those levels.
No we don't really know if it's enough to effect things or not. What needs to happen is we need to figure out the specs of the stock PCV valves and see if the vacuum levels seen are enough to open them up. The way I see it is at the stock locations those PCV valves were seeing A LOT of vacuum and now I doubt they're seeing any.
A PCV valve isn't neccesarily about manifold vacuum. I think it's geared more towards relieving built up pressure in the crankcase. The valve opens as the pressure rises and releases the vapor into the intake as a means of emmissions control.
The PCV valve is designed to open when it sees a vacuum not when it sees positive crankcase pressure.
Gary,
I don't see how the installer could've hooked it up wrong unless they decided that the T wasn't needed and they hooked up the passenger side PCV valve up to the stock location. That could be a real problem because the PCV valve would never open when the engine is on boost.
08-26-2003, 02:26 PM
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Honestly I think everyone is looking into this a bit to much......
It PCV system doesn't matter, as long as it's getting vented. There is no rocket science behind it. The VQ motor, follows all the same basic rules that motors have followed for many many years. Putting this much thought into the PCV system is like arguing about how to best tie your shoe. No matter how many ways you make a knot, you still end up with a shoe that is tied.
Also note that there is no way it could ever reach the same level as the manifold if conected to the intake side of any form of forced induction. That rule applies to both Turbos, and Superchargers.
The only reason why MAX's car was blowing oil out of the PCV system is that if in fact the ring lands went south. The pressure that is created durring combustion, was venting past the compression rings, then past the oil rings....down into the crank case, up wherever it wanted (valve covers) and out into the PCV system. The oil comming with it was just a by product of the massive amount of air moving thought the system that was never designed for that. Thus dragging some residual oil with it.
Even if the PCV system was pluged off completly, the car would not have suffered Ring land issues. Something along the lines of a blown rear main seal, or a blower valve cover gasket, oil dipstick tubes venting, etc. would be the issues, and NOT trashed ring lands.
To hurt ring lands takes detonation, abuse, lean conditions, (N20, or FI), bad gas, extended periods on the rev limiter, etc.
Lets not all get hung up on the small details, and try to over "engineer the wheel" Sorry I had to use that bad quote... LOL (unless you work for a wheel company) I just delt with all that way to much back when I was in school for Mechanical Engineering. Sometimes we can get so hung up on the details, to over look the obviouse.
Think outside the box,
EA
It PCV system doesn't matter, as long as it's getting vented. There is no rocket science behind it. The VQ motor, follows all the same basic rules that motors have followed for many many years. Putting this much thought into the PCV system is like arguing about how to best tie your shoe. No matter how many ways you make a knot, you still end up with a shoe that is tied.
Also note that there is no way it could ever reach the same level as the manifold if conected to the intake side of any form of forced induction. That rule applies to both Turbos, and Superchargers.
The only reason why MAX's car was blowing oil out of the PCV system is that if in fact the ring lands went south. The pressure that is created durring combustion, was venting past the compression rings, then past the oil rings....down into the crank case, up wherever it wanted (valve covers) and out into the PCV system. The oil comming with it was just a by product of the massive amount of air moving thought the system that was never designed for that. Thus dragging some residual oil with it.
Even if the PCV system was pluged off completly, the car would not have suffered Ring land issues. Something along the lines of a blown rear main seal, or a blower valve cover gasket, oil dipstick tubes venting, etc. would be the issues, and NOT trashed ring lands.
To hurt ring lands takes detonation, abuse, lean conditions, (N20, or FI), bad gas, extended periods on the rev limiter, etc.
Lets not all get hung up on the small details, and try to over "engineer the wheel" Sorry I had to use that bad quote... LOL (unless you work for a wheel company) I just delt with all that way to much back when I was in school for Mechanical Engineering. Sometimes we can get so hung up on the details, to over look the obviouse.
Think outside the box,
EA
08-26-2003, 10:30 PM
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I'm aware of Max's problems and the causes. I also realize the effects of ring land problems and plugged PCV systems.
I originally posted this to address Max's problems, but for me it evolved into some concerns once I really thought about the design.
I do know that PCV valves are not universal. They design PCV valves with specific vacuum levels for a reason. It isn't just one of those call it good things. I just don't see how the PCV system can be close to the Nissan engineered design the way it is.
It seems to me that ATI's PCV system is poorly thought out, with 2 valves going into one hose that's stuck at the end of the air filter it can't possible be metering the venting of the crankcase properly. I'm not a mechanical engineer though, if you are and you say it's ok, that makes me feel better although not completely.
Can you tell me then why when at an idle with the ATI designed system at an idle it is very rough with a variation of a couple hundred RPM, and when I put the PCV hoses back in their original location the idle is considerably better? The only thing I've done is to move one of the lines to it's stock location and pinch off the other.
I originally posted this to address Max's problems, but for me it evolved into some concerns once I really thought about the design.
I do know that PCV valves are not universal. They design PCV valves with specific vacuum levels for a reason. It isn't just one of those call it good things. I just don't see how the PCV system can be close to the Nissan engineered design the way it is.
It seems to me that ATI's PCV system is poorly thought out, with 2 valves going into one hose that's stuck at the end of the air filter it can't possible be metering the venting of the crankcase properly. I'm not a mechanical engineer though, if you are and you say it's ok, that makes me feel better although not completely.
Can you tell me then why when at an idle with the ATI designed system at an idle it is very rough with a variation of a couple hundred RPM, and when I put the PCV hoses back in their original location the idle is considerably better? The only thing I've done is to move one of the lines to it's stock location and pinch off the other.
08-26-2003, 11:10 PM
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I just reread my post and it seemed to me like I might have been a little bit of a smart@ss in my post. That was not my intent. I do know a thing or two about engines though and I guess I felt a little talked down to.
08-27-2003, 06:20 AM
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On the ATI system I installed, the idle improved dramatically after the installation.
I really think you are over thinking this. I really don't think there is a problem with ATI's design. Again, this is my opinion...
As long as there is a way to relieve the pressure in the engine, it doesn't matter if ten hoses lead into one. I don't know how many other cars you have worked on, but there are many older cars, mostly from the sixties for example, that have an identical set up. Also, on some newer cars I am familiar with, there are two hoses that lead into one, the new Corvettes for example.
With Max's set up, he could have been the victim of simply a poor installation. As we are finding out, it is more than that. A plugged PCV system will not melt ring lands. I think we are learning this is getting to be more of a case of abuse and poor tuning than anything else. The oil problem is simply a by product. Anyway, just my thoughts.
I really think you are over thinking this. I really don't think there is a problem with ATI's design. Again, this is my opinion...
As long as there is a way to relieve the pressure in the engine, it doesn't matter if ten hoses lead into one. I don't know how many other cars you have worked on, but there are many older cars, mostly from the sixties for example, that have an identical set up. Also, on some newer cars I am familiar with, there are two hoses that lead into one, the new Corvettes for example.With Max's set up, he could have been the victim of simply a poor installation. As we are finding out, it is more than that. A plugged PCV system will not melt ring lands. I think we are learning this is getting to be more of a case of abuse and poor tuning than anything else. The oil problem is simply a by product. Anyway, just my thoughts.
08-27-2003, 07:05 AM
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I'm sure there are many cars with similar setups. But the corvette example you gave was designed from the factory like that, right? as I'm sure the cars from the sixties. The systems were set up to operate with a certain amount of vacuum and now we've put a system that was supposed to be running a high vacuum at idle to one with almost no vacuum because the hose is stuck at the end of a high flow K&N filter. I'd be surprised if the PCV system is seeing any vauum at all at idle. Maybe I am overthinking this though.
This is my thoughts of how the system is supposed to operate and how it operates now with the new PCV setup. I realize it'd be hard to create the same amount of vauum, but the way I see it this system is setup to do the exact opposite of what we want.
Stock system = BLACK
ATI System = RED
Idle = High Manifold Vacuum, Low Crankcase Pressure, PCV mostly closed
Idle = Low/none Intake Vacuum, Low Crankcase Pressure, PCV mostly open
At idle the system might work ok because the PCV valve should be wide open. Unless there is no intake vacuum (as I believe the case to be) caused by the big *** K&N filter.
Partial load = Moderate Manifold Vacuum, Moderate Crankcase Pressure, PCV at medium crankcase setting
Partial load = Moderate Intake Vacuum, Moderate Crankcase Pressure, PCV at medium crankcase setting
Partial load might be ok, assuming that there is enough vacuum to open the PCV valve to the proper position.
High engine load = Low Manifold Vacuum, High Crankcase Pressure, PCV at mostly open setting
High engine load = High Intake Vacuum, High Crankcase Pressure, PCV at mostly closed setting
This is the opposite of what we want. The more intake vacuum there is... the less venting of gasses.
If you guys aren't worried about it though, maybe I should stop worrying about it too, but I see potential problems and I'm not talking about problems with the rings, I'm talking about overpressurizing of the crankcase = blowing seals and improper venting of damaging corrosive gasses, which as the engine cools condense on various internal engine components and cause rust and pitting of surfaces.
This is my thoughts of how the system is supposed to operate and how it operates now with the new PCV setup. I realize it'd be hard to create the same amount of vauum, but the way I see it this system is setup to do the exact opposite of what we want.
Stock system = BLACK
ATI System = RED
Idle = High Manifold Vacuum, Low Crankcase Pressure, PCV mostly closed
Idle = Low/none Intake Vacuum, Low Crankcase Pressure, PCV mostly open
At idle the system might work ok because the PCV valve should be wide open. Unless there is no intake vacuum (as I believe the case to be) caused by the big *** K&N filter.
Partial load = Moderate Manifold Vacuum, Moderate Crankcase Pressure, PCV at medium crankcase setting
Partial load = Moderate Intake Vacuum, Moderate Crankcase Pressure, PCV at medium crankcase setting
Partial load might be ok, assuming that there is enough vacuum to open the PCV valve to the proper position.
High engine load = Low Manifold Vacuum, High Crankcase Pressure, PCV at mostly open setting
High engine load = High Intake Vacuum, High Crankcase Pressure, PCV at mostly closed setting
This is the opposite of what we want. The more intake vacuum there is... the less venting of gasses.
If you guys aren't worried about it though, maybe I should stop worrying about it too, but I see potential problems and I'm not talking about problems with the rings, I'm talking about overpressurizing of the crankcase = blowing seals and improper venting of damaging corrosive gasses, which as the engine cools condense on various internal engine components and cause rust and pitting of surfaces.
08-27-2003, 07:29 AM
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Jess, No offence was taken. I fully understand where you are comming from. I just didn't want people that are lurking think this is some big ordeal. So I hope you don't take offence to my posts.
The PCV system yes, is different for each car. But the overall operation is universal.
If you have a idle change when you are connecting and disconnecting, then you have a vacuum leak. There is no other reason under the sun. If I was you I would start double checking for a leak, or crack. Since the 350Z doesn't meter the air untill about 4" away from the TB with the ATI kit, I find this very hard to believe, unless a leak is found.
I would say check that everything is tight, even on the back drivers side valve cover, the nipple on the top side of the intake (pass side) and others. Also make sure that the vacuum tree that you add to the system is fully tight, and has the plug installed.
As I have stated I am VERY educated when it comes to forced induction, (3 of my 4 cars feature either a blower or turbo) as well as have hands on put 5 350Z kits on now for friends. I have not had any issues with the idle issue you speak of. I'm just hear to learn and help out. I don't know if that eases your mind. But I will be the first person to say "I don't know" if for a moment I don't think I can answer a question, or haven't experienced it myself. I would rather shrug my shoulders, then give anyone a guess for an answer.
Blck mgc, glad to see that you are on the same page.
EA
The PCV system yes, is different for each car. But the overall operation is universal.
If you have a idle change when you are connecting and disconnecting, then you have a vacuum leak. There is no other reason under the sun. If I was you I would start double checking for a leak, or crack. Since the 350Z doesn't meter the air untill about 4" away from the TB with the ATI kit, I find this very hard to believe, unless a leak is found.
I would say check that everything is tight, even on the back drivers side valve cover, the nipple on the top side of the intake (pass side) and others. Also make sure that the vacuum tree that you add to the system is fully tight, and has the plug installed.
As I have stated I am VERY educated when it comes to forced induction, (3 of my 4 cars feature either a blower or turbo) as well as have hands on put 5 350Z kits on now for friends. I have not had any issues with the idle issue you speak of. I'm just hear to learn and help out. I don't know if that eases your mind. But I will be the first person to say "I don't know" if for a moment I don't think I can answer a question, or haven't experienced it myself. I would rather shrug my shoulders, then give anyone a guess for an answer.
Blck mgc, glad to see that you are on the same page.
EA
08-27-2003, 07:49 AM
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I am going to check that plug on the vacuum tree. It could be loose and causing my idle problems. Time to break out the starting fluid I guess.
What about how the PCV system is supposed to operate and how it now operates as described in my post above. Do you have any comments on the changes made to it?
What about how the PCV system is supposed to operate and how it now operates as described in my post above. Do you have any comments on the changes made to it?
08-27-2003, 08:21 AM
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I hope these corrections will answer your questions. And yes starting fluid time Gotta love the "Leak check in a can" thanks to the wonderfull world of Ether.
[B] The PCV is just a check valve.
Stock system = BLACK
ATI System = RED
EA's Corrections = GREEN
Idle = High Manifold Vacuum, Low Crankcase Pressure, PCV mostly open
Idle = Low/none Intake Vacuum, Low Crankcase Pressure, PCV mostly open
FACT = There is no difference they are both open.
At idle the system might work ok because the PCV valve should be wide open. Unless there is no intake vacuum (as I believe the case to be) caused by the big *** K&N filter.
The filter has NOTHING to do with the system, and please don't use this reference again. In fact this system would work the same if it was vented into the air. The PCV system is a fancy word for a check valve. IT is OPEN any time there is .000001" to 20"+ of vacuum. The ONLY time it closes is the following. Once the motor hits full throttle the TB opens, vacuum is gone ( o" and or 0psi) on NA cars as well as FI cars. The check valve then "can" shut (note the key word "can"). With a FI car/truck/boat/plane/go kart/etc, it is best to keep this valve on the intake side of the blower or turbo, so that there is never a chance to crank case pressure if the PCV check valve was to fail. If the PCV valve got gummed up with oil or something, to could stick, then let boost pressure bleed into the crank case.
Partial load = Moderate Manifold Vacuum, Moderate Crankcase Pressure, PCV at OPEN crankcase setting
Partial load = Moderate Intake Vacuum, Moderate Crankcase Pressure, PCV at OPEN crankcase setting
Only minor corrections on this
High engine load = Zero Manifold Vacuum, High Crankcase Pressure, PCV Neutral or shutting (this goes hand and hand with my "can" description above
High engine load = High Intake Vacuum, High Crankcase Pressure, PCV at OPEN setting
FACT: Since the ATI system is in the intake side, when the crank case pressure goes up, even under wide open throttle, it lets it vent as much as it wants, and also aids it by venting since the blower is sucking in air a a very rapid rate. (This also is the same for a turbo set up)
If you guys aren't worried about it though, maybe I should stop worrying about it too, but I see potential problems and I'm not talking about problems with the rings, I'm talking about overpressurizing of the crankcase = blowing seals and improper venting of damaging corrosive gasses, which as the engine cools condense on various internal engine components and cause rust and pitting of surfaces.
It will be ok, honestly, do not worry about this small item. Worry about who is going to be the first tuner, to let you have full control of the computer thats something worth thinking about.
EA
Gotta love the "Leak check in a can" thanks to the wonderfull world of Ether. [B] The PCV is just a check valve.
Stock system = BLACK
ATI System = RED
EA's Corrections = GREEN
Idle = High Manifold Vacuum, Low Crankcase Pressure, PCV mostly open
Idle = Low/none Intake Vacuum, Low Crankcase Pressure, PCV mostly open
FACT = There is no difference they are both open.
At idle the system might work ok because the PCV valve should be wide open. Unless there is no intake vacuum (as I believe the case to be) caused by the big *** K&N filter.
The filter has NOTHING to do with the system, and please don't use this reference again. In fact this system would work the same if it was vented into the air. The PCV system is a fancy word for a check valve. IT is OPEN any time there is .000001" to 20"+ of vacuum. The ONLY time it closes is the following. Once the motor hits full throttle the TB opens, vacuum is gone ( o" and or 0psi) on NA cars as well as FI cars. The check valve then "can" shut (note the key word "can"). With a FI car/truck/boat/plane/go kart/etc, it is best to keep this valve on the intake side of the blower or turbo, so that there is never a chance to crank case pressure if the PCV check valve was to fail. If the PCV valve got gummed up with oil or something, to could stick, then let boost pressure bleed into the crank case.
Partial load = Moderate Manifold Vacuum, Moderate Crankcase Pressure, PCV at OPEN crankcase setting
Partial load = Moderate Intake Vacuum, Moderate Crankcase Pressure, PCV at OPEN crankcase setting
Only minor corrections on this
High engine load = Zero Manifold Vacuum, High Crankcase Pressure, PCV Neutral or shutting (this goes hand and hand with my "can" description above
High engine load = High Intake Vacuum, High Crankcase Pressure, PCV at OPEN setting
FACT: Since the ATI system is in the intake side, when the crank case pressure goes up, even under wide open throttle, it lets it vent as much as it wants, and also aids it by venting since the blower is sucking in air a a very rapid rate. (This also is the same for a turbo set up)
If you guys aren't worried about it though, maybe I should stop worrying about it too, but I see potential problems and I'm not talking about problems with the rings, I'm talking about overpressurizing of the crankcase = blowing seals and improper venting of damaging corrosive gasses, which as the engine cools condense on various internal engine components and cause rust and pitting of surfaces.
It will be ok, honestly, do not worry about this small item. Worry about who is going to be the first tuner, to let you have full control of the computer
thats something worth thinking about. EA
Last edited by TheSVTKid; 08-27-2003 at 08:27 AM.
08-27-2003, 08:35 AM
#19
Jesse, I think what you're saying makes sense, and it is logically correct assuming a certain type of pcv valve. However, I also don't know that it should be a concern. Of all the ATI installs out there, we only see a portion of them on this forum of course. But out of those, how many have exhibited any symptoms of execessive crankcase pressure? The only one is Max, and apparently it is now known that the rings are cracked, which is the cause of the crankcase pressure for him. I'm not disagreeing with you, but at this point I don't know how we can determine if there really is a concern with the rerouted pcv line.
I actually have another possibility for supporting the idea that the system is indeed working correctly on our ATI cars. Looking at the stock system, one pcv is plumbed into the intake plenum while the other is plumbed into the intake pipe before the throttle body. This means that the two valves are seeing different operating conditions.
Now, out of the two valves, the one before the throttle body most closely matches the conditions they now both see with the ATI kit. Hopefully this makes sense. The valve I'm referring to (driver's side), in order to operate in unison with the other valve, would have to work differently from the way you are assuming both valves work. Hence, under low vacuum conditions, it would be open less than under high vacuum conditions. So based on this logic, the driver's side valve would work properly with the ATI kit in theory. If anybody knows for a fact that both valves are the same, you can off course completely debunk what I'm saying here.
Assuming that these valves don't work exactly the same, we could have a case where there is always a fairly large combined opening between the two. What I'm saying is that if one is close, the other is open, or both could be opened by close to the same amount. In the end, this means there should be more than enough flow capacity through the combination of the two valves at all times to get rid of the crankcase vapors and prevent excessive crankcase pressure.
Just an idea...I haven't verified any of this
I actually have another possibility for supporting the idea that the system is indeed working correctly on our ATI cars. Looking at the stock system, one pcv is plumbed into the intake plenum while the other is plumbed into the intake pipe before the throttle body. This means that the two valves are seeing different operating conditions.
Now, out of the two valves, the one before the throttle body most closely matches the conditions they now both see with the ATI kit. Hopefully this makes sense. The valve I'm referring to (driver's side), in order to operate in unison with the other valve, would have to work differently from the way you are assuming both valves work. Hence, under low vacuum conditions, it would be open less than under high vacuum conditions. So based on this logic, the driver's side valve would work properly with the ATI kit in theory. If anybody knows for a fact that both valves are the same, you can off course completely debunk what I'm saying here.
Assuming that these valves don't work exactly the same, we could have a case where there is always a fairly large combined opening between the two. What I'm saying is that if one is close, the other is open, or both could be opened by close to the same amount. In the end, this means there should be more than enough flow capacity through the combination of the two valves at all times to get rid of the crankcase vapors and prevent excessive crankcase pressure.
Just an idea...I haven't verified any of this
08-27-2003, 08:57 AM
#20
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AAAHHH, now I see where you are coming from now, but I'm still gonna be stubborn about this one. Don't all modern cars now use pintle type system, to reduce the drastic vacuum change from closed to open. This is what I'm getting at. Check valves are old school.
