Yes..another crank case pressure thread
03-03-2018, 06:46 PM
#22
Melting Slicks
What isn't obvious is the one way valve below that, that only allows pressure out, unlike just a filter on a valve cover. So no, it does not work exactly the same as a filter on a valve cover. On the MM cans it is a safety device for an over pressure situation, not just an open filter all the time.
stop being hard headed and separate part throttle from WOT in your head. The MM can behaves identical to the filter on the valve cover at WOT.
and since you brought it up what the hell lets look at part throttle venting as well. Oh look, intake manifold vacuum suction through a hose appears the draw on the crankcase, through a can. Exactly like the OP had to begin with, a separator between valve cover and intake part throttle suction. Hmm I see no difference!
Last edited by Kingtal0n; 03-03-2018 at 06:49 PM.
03-03-2018, 07:02 PM
#23
Melting Slicks
I think we should do an overview of factory PCV
The crankcase is like a cup. the valvecover is like the lid. You have 2 lids on this cup amirite?
Lid#1 The factory uses 1 lid to feed the intake manifold. This is for part throttle. there is a check valve on this line called a 'pcv valve' but its just a regular check valve, 1-way.
Lid#2 The other lid is for air that enters the crankcase to replace what the first lid takes out of the crankcase during part throttle. This lid also serves a reverse-duty as well: It allows air out of the crankcase during WOT/boost, when the check valve from the other lid is closed tight.
So lets look more closely at lid#1 and lid#2
Lid#2 is essential, because without a fresh air source the crankcase would not last long. Seal this hole up and pressure will push oil from every seal. Vacuum could do the same thing in reverse: pull every seal into the engine. This is the most important hole in the crankcase because it prevents these two extreme catastrophes.
Lid #1 run to the intake manifold vacuum for part throttle is optional. Some people run this to exhaust system, or a vacuum pump, or don't use it at all. Using it is important for oil quality and engine longevity; but if you change the oil far more than usual the impact of carbon byproduct filth is lessened overall, because contaminants that would have been taken up by crankcase evacuation (pcv) system are removed with oil changes (most of them, although some stick around on parts so it isn't a complete cleaning).
Crankcase pressure requirement: Lid #2 if it was just a huge open hole, there would never be any pressure lowering the crankcase during normal operation. The factory pcv system uses a restrictor here to improve crankcase vacuum signal, which improves ring seal, economy, and oil cleanliness as lid#1 draws on the crankcase through the restrictor in lid#2.
Pressure can be measured using a gauge which reads in inches of water for this operation constant.
Finally, during WOT on a factory engine, Lid #2 feeds from an area behind the OEM paper air filter element. The pressure there is lower than atmospheric on a sightly dirty paper filter, around 12-20" of Water is common. This low pressure signal is fed through Lid#2 at WOT to the crankcase, such that, while Lid#1 is shut tight because of the checkvalve action, the crankcase is still able to achieve some semblance of PCV action (pressure below atomspheric).
This is the part of the system that the MM catch can deletes (it was already deleted on the op's photos anyways) and the part of the system which I had discussions about. The increased ring seal at WOT is negligible and the excess carbon byproduct is arguably negligible as well considering the oil change frequency for most owners is higher than average vehicles on the road, which is why I shrugged at the loss of this part of the pcv system for most cars.
The crankcase is like a cup. the valvecover is like the lid. You have 2 lids on this cup amirite?
Lid#1 The factory uses 1 lid to feed the intake manifold. This is for part throttle. there is a check valve on this line called a 'pcv valve' but its just a regular check valve, 1-way.
Lid#2 The other lid is for air that enters the crankcase to replace what the first lid takes out of the crankcase during part throttle. This lid also serves a reverse-duty as well: It allows air out of the crankcase during WOT/boost, when the check valve from the other lid is closed tight.
So lets look more closely at lid#1 and lid#2
Lid#2 is essential, because without a fresh air source the crankcase would not last long. Seal this hole up and pressure will push oil from every seal. Vacuum could do the same thing in reverse: pull every seal into the engine. This is the most important hole in the crankcase because it prevents these two extreme catastrophes.
Lid #1 run to the intake manifold vacuum for part throttle is optional. Some people run this to exhaust system, or a vacuum pump, or don't use it at all. Using it is important for oil quality and engine longevity; but if you change the oil far more than usual the impact of carbon byproduct filth is lessened overall, because contaminants that would have been taken up by crankcase evacuation (pcv) system are removed with oil changes (most of them, although some stick around on parts so it isn't a complete cleaning).
Crankcase pressure requirement: Lid #2 if it was just a huge open hole, there would never be any pressure lowering the crankcase during normal operation. The factory pcv system uses a restrictor here to improve crankcase vacuum signal, which improves ring seal, economy, and oil cleanliness as lid#1 draws on the crankcase through the restrictor in lid#2.
Pressure can be measured using a gauge which reads in inches of water for this operation constant.
Finally, during WOT on a factory engine, Lid #2 feeds from an area behind the OEM paper air filter element. The pressure there is lower than atmospheric on a sightly dirty paper filter, around 12-20" of Water is common. This low pressure signal is fed through Lid#2 at WOT to the crankcase, such that, while Lid#1 is shut tight because of the checkvalve action, the crankcase is still able to achieve some semblance of PCV action (pressure below atomspheric).
This is the part of the system that the MM catch can deletes (it was already deleted on the op's photos anyways) and the part of the system which I had discussions about. The increased ring seal at WOT is negligible and the excess carbon byproduct is arguably negligible as well considering the oil change frequency for most owners is higher than average vehicles on the road, which is why I shrugged at the loss of this part of the pcv system for most cars.
03-03-2018, 08:45 PM
#24
Thanks Todd, I think you are correct re the gauge. However, since all the readings are fairly close (i.e no huge discrepancy like there would be for a cracked piston), I think the motor is still in pretty good shape. Im going to pull off the boost anyway, so as long as nothing is busted, I know I dont need a bottom end rebuild..right now at least. Regardless Im going to add a MM mild catch can since I think it will help now and when I am NA.
KJ
KJ
03-19-2018, 08:12 AM
#26
Burning Brakes
Yup start with a MM or Elite catch can setup. I have used Elite with a VC breather on three LS builds without problem.
03-19-2018, 12:43 PM
#27