2014 Blue RS
Active member
Got it! Thank you sir.
Fixing the intake manifold and PCV for good
- Thread starter Flyer
- Start date
I'm not sure what the critique is specifically. Please don't take this as a dispute, but more of a discussion.
The diaphragm (probably better description) is there to vent excessive pressure. Ideally the boost pressurizing the crankcase should be vented to the PCV line which dumps just upstream from the turbo. We have seen a couple of vehicles come in with oil being pushed out of the seals and mating surfaces. It's not all the time though.
With what I did .. there will never be boost enter the crankcase, unless there is blow by from pistons. That's a completely different issue though. With what I did, the PCV vents neutrally through the catch can. The port in the intake for the PCV is blocked off entirely so there is nothing coming in from the crankcase into the intake or out of the intake into the PCV hose in front of the turbo) bleeding boost.
Playing devil's advocate, I think an 80 (I'm not sure of the price for sure) valve cover is hardly a maintenance item. The intake is certainly not a maintenance item either.
In a more official statement, GM doesn't cover maintenance in any way shape form or fashion under warranty. The cover and intake both are covered under the powertrain warranty.
The diaphragm (probably better description) is there to vent excessive pressure. Ideally the boost pressurizing the crankcase should be vented to the PCV line which dumps just upstream from the turbo. We have seen a couple of vehicles come in with oil being pushed out of the seals and mating surfaces. It's not all the time though.
With what I did .. there will never be boost enter the crankcase, unless there is blow by from pistons. That's a completely different issue though. With what I did, the PCV vents neutrally through the catch can. The port in the intake for the PCV is blocked off entirely so there is nothing coming in from the crankcase into the intake or out of the intake into the PCV hose in front of the turbo) bleeding boost.
Playing devil's advocate, I think an 80 (I'm not sure of the price for sure) valve cover is hardly a maintenance item. The intake is certainly not a maintenance item either.
In a more official statement, GM doesn't cover maintenance in any way shape form or fashion under warranty. The cover and intake both are covered under the powertrain warranty.
mja
Site Supporter
There should never be boost in the crank case, the check valves in the PCV system are there to prevent this from happening.
The intake manifold valve allows manifold and crankcase vacuum to equilibrate under idle or part throttle. The turbo inlet check valve is closed under vacuum. When the manifold vacuum sees excessive pressure, the intake manifold check valve closes and allows crank pressure to move to intake manifold, but not the reverse.
In the reverse way, the turbo inlet check valve opens under boost as the manifold check valve closes. This again allows crank pressure to be relieved or recirculated.
What you've done is closed off the idle/part throttle PCV system, and allowed crank pressure to be relieved only under strong boost. Which is perfectly fine in a track car, but not for a street car that sees most of it's active duty at idle or part throttle
This will stress the turbo inlet check valve. Walker has already made posts about the turbo ring seals. A faulty turbo check valve could force oil past the turbo ring seals, *or starve the bearings of oil if pressure drops, do a forum search.
Also you've removed the biggest safety check on the PCV system - the diaphragm. What happens when excess pressure builds up? I guess you'll find out.
The diaphragm is a design which is meant to break with use or when engine conditions are unfavorable; maintenance items are usually designed to wear or fail over time. I guess you could call it a safety item, sure.
Good luck.
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mja
Site Supporter
Read MPFab's and Preloaders posts here, good info:
http://www.sonicownersforum.com/forum/1-4l-turbo-sonic-engine-discussion/6697-turbo-seals.html
There's been more than a few times turbos have blown that can be tracked back to PCV issues. There have also been piston rings and crank seals go from similar issues.
http://www.sonicownersforum.com/forum/1-4l-turbo-sonic-engine-discussion/6697-turbo-seals.html
There's been more than a few times turbos have blown that can be tracked back to PCV issues. There have also been piston rings and crank seals go from similar issues.
I think you are missing that my PCv is not sealed off. The spot where the diaphragm was is now hollowed out with a 3/4 pipe fitting shoved in there to vent the baffled area. There is a 3/8 hose attached to that fitting which is vented to the atmosphere through a catch can and filter.
Sealing the crankcase would cause the issues you are referencing. My crankcase is not sealed. The port in the intake is so that the PCv will never get into the crankcase anymore.
Sealing the crankcase would cause the issues you are referencing. My crankcase is not sealed. The port in the intake is so that the PCv will never get into the crankcase anymore.
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mja
Site Supporter
So all this is, is a crank breather. This wasn't mentioned in any of the write up posts, I reread them a couple times. It was mentioned you routed to the catch can and that was the extent of the PCV system, so my assumption was it was routed to a PCV system.
You may want to update that so people don't reroute and build crankcase pressure. I thought you were recirculating crank pressure from the blocked off diaphragm. Thank you for the clarification, I'm sure others on the forum will appreciate that bit of info.
mja
Site Supporter
Thank you for getting this writeup to everyone. There are some negatives to crankcase breathing, but if the alternative is to blow intake mani, cam cover, coil pack, and turbo, it couldn't hurt.
Im curious exactly how the vacuum bladder operates under the intake mani. Does it only supply the BPV?
Im curious exactly how the vacuum bladder operates under the intake mani. Does it only supply the BPV?
Yes. It leaches off the intake manifold for vacuum using that same little check valve that's used in the PCV port of the manifold. It supplies vacuum so the solenoid for the BPS valve can operate under boost.
That's why bypassing the boss I think has you just capping that fitting on the bottom.
That's why bypassing the boss I think has you just capping that fitting on the bottom.
mja
Site Supporter
I'm curious where you're pulling vacuum for the BPV, on the intake somewhere?
mja
Site Supporter
So bypass the BPV solenoid + crankcase breather, not a bad idea at all for a race car.
Will make a thread about adding an external vacuum *canister with check valve, circumventing the need for the stock orange check valve, whenever parts come in.
Nothing against guys running the 'bypass the bypass' mod, but I don't trust supplying the BPV with manifold vacuum when the system was designed for a consistent low vac source.
Will make a thread about adding an external vacuum *canister with check valve, circumventing the need for the stock orange check valve, whenever parts come in.
Nothing against guys running the 'bypass the bypass' mod, but I don't trust supplying the BPV with manifold vacuum when the system was designed for a consistent low vac source.
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The bladder is there for the ECM to nanny the boost.
The BPV will open under a defined pressure ration according to how much air is moving across the MAF. There are some other parameters that will cause the ECM to command the BPV open.
Bypassing the bypass with take this control away from the computer. It restores the conventional method where the BPV will open when the manifold sees vacuum (under boost and the throttle blade closes). As oppose where the ECM looks for a commanded and measured difference to determine when the BPV should open.
The table is at what Pressure Ratio the BPV will open compared to how much air is flowing into the motor.
-Prepare for really technical stuff-
The other things aren't as easy to explain. In short, if there is that much of a difference between boost (measured in charge pipe I believe), and the manifold pressure measurement the BPV will open. Remember pressure is relative. 75 kpa, while is considered to be in vacuum, it is still pressure in a technical sense. 0 KPA would be no pressure where 100-105 kpa would be atmospheric pressure (neutral to us).
The BPV will open under a defined pressure ration according to how much air is moving across the MAF. There are some other parameters that will cause the ECM to command the BPV open.
Bypassing the bypass with take this control away from the computer. It restores the conventional method where the BPV will open when the manifold sees vacuum (under boost and the throttle blade closes). As oppose where the ECM looks for a commanded and measured difference to determine when the BPV should open.
The table is at what Pressure Ratio the BPV will open compared to how much air is flowing into the motor.
-Prepare for really technical stuff-
The other things aren't as easy to explain. In short, if there is that much of a difference between boost (measured in charge pipe I believe), and the manifold pressure measurement the BPV will open. Remember pressure is relative. 75 kpa, while is considered to be in vacuum, it is still pressure in a technical sense. 0 KPA would be no pressure where 100-105 kpa would be atmospheric pressure (neutral to us).
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mja
Site Supporter
Thank you for the tune tables Flyer, I love that type of thing. I used to tune a long time ago, so no worries about throwing out technical stuff.
My curiosity is peaked as to why those with PCV issues and stock BPV solenoids are having problems with decreased turbo life. From a mechanical standpoint it makes sense, there is no control over BPV solenoid if the switch isn't supplied with constant vacuum. It seems when this solenoid is defective, the resulting problems are worse than bypassing it entirely and using manifold pressure. My thought is to make a setup which uses the stock PCV system but an aftermarket canister where the check valve is more reliable.
Do the tune files show what other parameters the ECM commands the BPV solenoid open or closed?
My curiosity is peaked as to why those with PCV issues and stock BPV solenoids are having problems with decreased turbo life. From a mechanical standpoint it makes sense, there is no control over BPV solenoid if the switch isn't supplied with constant vacuum. It seems when this solenoid is defective, the resulting problems are worse than bypassing it entirely and using manifold pressure. My thought is to make a setup which uses the stock PCV system but an aftermarket canister where the check valve is more reliable.
Do the tune files show what other parameters the ECM commands the BPV solenoid open or closed?
Those are all of the parameters. Pcv and bpv are 2 totally different circuits shared only by the manifold. The Pcv dumps oil into the turbo inlet. Liquids don't compress and are a lot harder to move through a high speed compressor wheel than air. The bpv circuit is prone to oil consumption due to the Pcv pumping oil into the manifold and the vacuum bladder being on the bottom to absorb all the oil.
mja
Site Supporter
I get the 2 circuits. The PCV blows oil into the solenoid line and the BPV fails when the system fails, at the same time pushes oil into the turbo inlet.
So is the purpose of commanding the BPV solenoid off MAF to prevent a rich AFR when the solenoid activates? Otherwise, what's the purpose of the BPV solenoid :blankface:
So is the purpose of commanding the BPV solenoid off MAF to prevent a rich AFR when the solenoid activates? Otherwise, what's the purpose of the BPV solenoid :blankface:
So, someone can essentially do this without chopping the tank. All we would have to do is plug the hose at the bottom. Which causes bypass Solenoid issues? So we disable the P0 codes with our tuning software and we should be good? is that right? I already have the bpv directly connected to the manifold pressure port(passenger side)