In a forced induction application they are TIGHTLY CLOSED. This is the ideal and the goal behind PCV.
If the PCV valve is blown open it means there is too much crankcase pressure- PCV has failed in a natural aspirated application, which is benign blow-by compared to a forced induction engine. Now the intake will fill with oil. Just because all the engines you work on do this and its how the PCV valve is designed to relief crankcase pressure doesn't make it an optimal or ideal solution or even necessary. Stop regurgitating what you are reading and think for yourself is my advice. Compare the crankcase pressure to the intake manifold pressure and ask yourself where does the differential begin, where does it end, what is the difference in pressure between the crankcase and intake manifold and how will that affect the PCV valve.
Flow against the check valve causes it to check- sealed shut. The PCV Valve has low flow and high flow position. High flow is failed PCV in a natural aspirated application. Low flow is the goal, low or no flow.
To achieve this end the flow direction must be away from the PCV Valve, into the crankcase. To achieve this in a natural aspirated application the other side of the engine away from the PCV valve requires a low enough pressure difference to drive flow away from the PCV valve's corner of the engine.
Blow-by raises pressure of crankcase over atmospheric- tries to. Air filter restrictions drops the intake plumbing below atmospheric which pulls the pressure of the crankcase below atmospheric, pulling out blow-by and pulling the PCV valve into a low-flow or no flow condition, checked. If it is properly connected like OEM and utilizes the correct air filter. There is also some momentum flow and conservation of energy at work.
If we remove the air filter from the engine the intake plumbing rises to atmosphere. Now the crankcase pressure can also rise above atmosphere. This is why and how the PCV Valve blows wide open 'high flow' and oil is entering the intake manifold without forced induction to slam the PCV Valve shut.
I can't see The Professor's posts, so I don't know whether he's admitting incorrect assumptions or doubling down. (Based on previous interactions my money's on doubling down.)
I saw a textbook posted on the previous page, only because someone quoted it. I did not read it. Because, again, previous interactions tell me that's not a productive thing to do. But I saw that it existed.
Then, the other post was quoted, the one I responded to. Which pretty much justifies my policy of not reading The Professor's textbook-style posts. Because, if someone writes a textbook on a subject but hasn't bothered to understand the device they're writing about, that's probably a person you should not take advice from.
Its called plasticity.
I like blindsquirrel, I think hes a great asset to the forum. I told him many times. I appreciate him. But hes too old to take in new information I guess.
If you do not want to become stuck in place, you need to read every day new information. New books. Learn new skills. Then, it will be easy to say "I don't know"
The body is a vehicle with limitations set by nature, but these are more like guidelines. Its up to us how far we walk the guide, and how far to step outside the line.
vent rocker covers to air or intake before TB so they dont see vacuum, then if u have crank breather i usually do the same, i dont like vacuum as that is what sucks all the oil vapor thru and u dont need it at idle but when ur full throttle the intake is seeing the same as the vacuum would have anyway so it works just using the intake before TB, also using bigger hose helps slow the air speed down so it dosnt draw as much oil with it, venting to intake will show least oil if any but will catch water/condensation u will have to empty out more so in winter
If the crankcase has a breather oil can bypass the lines and go right into the cylinder through the piston rings. It will make the problem even worse.
https://www.corvetteforum.com/forums...post1606137830
-Greg Banish
Calibrated Success, Inc.
Crankcase pressure is misunderstood as I have said. It will force piston rings up and away from the cylinder wall at the end of power stroke. It will force oil into the piston rings. Over time oil accumulates in the rings causing them to stick as light hydrocarbons leave. This leads to stuck rings, excessive wear, eventual failure.
Blow-by which isn't properly evacuated also carries partially reacted hydrocarbon molecules into the oil system, circulates blow-by products which leads to deposits and eventual wear and failure.
Using a breather is a good way to destroy an engine.
Your PCV routing isn't right.
Clean air from before throttle plate to both valve covers. PCV from valley cover to catchcan (sealed) to vacuum.
Also, Alvin is correct in saying that high oil temperatures will increase oil vapors pulled from the crankcase.
That's it. That's all.
Last edited by SiriusC1024; 09-08-2023 at 01:23 AM.
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Oil takes longer to warm up.. I'll bet 25min+ into a drive your oil temps would be 280F +
I'm serious.
When this happen they become bastards about spark knock. I'd take time to check this ASAP.. Like I said though it takes a good long while for oil temps to catch up. So 25+ min.. Or drive it warm the water up completely. Park it for 30 min then go for another ride.
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I appreciate the help Alvin. I currently don't have any way to measure oil temp but I have not had any issues with knock according to my logs. I just placed the order for a sealed top for the catch can and one of those Radium Engineering PCV valves that THE MECHANIC linked in a previous post. Does that sound like it will work? FWIW, i have aftermarket valve covers- Proform.
if u have the e38 then it should have the oil temp input, then a GM oil temp sensor (we have it in the oil level/temp sensor in sump 3 wire) not sure if thats suitable to suit your setup
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The consistency of the cylinder pressures look normal and in what I would expect as far as pressure. The catch can is a completely different topic. A catch can should be used when there is direct injection (fuel directly pumped into the cylinder and not the intake manifold. Gen V LS are direct injection. GM does not put a catch can in from the factory. The flaw is the fuel in the intake manifold creates a cleaning/anti-gum characteristic helping the valves to stay clean. Direct injection then doesn't have the fuel for cleaning AND with crankcase ventilation into the intake (vacuum) this provides the gunk to foul the valves. A catch can/mist eliminator removes the gunk from the PCV and helps the intake to stay cleaner. The spinning of the crankshaft creates turbulence and vaporizes small amounts of oil which gets sucked out with PCV. In the dark ages (pre-1970ish pre-EPA standards), there was no PCV and we used a vented cap in the valve cover. JLT Performance makes a great catch can kit for the LS motors. I installed mine on my 2019 Silverado LD, direct injection, and get 2 tablespoons of really thick "oil" between my 8K oil changes. The truck has 34K miles on it. If you don't have any intake vacuum connections to the crankcase/valve covers, you will get something "blowing out" from somewhere because there is a positive pressure in the crankcase and valve train. A simple check valve and vacuum line will do the same as a PCV setup.
Bernie Pella
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You aren't schooling anyone here. You post like you have an inferiority complex.
Maybe you should take all that copy and paste knowledge and go back and try to figure out the difference between GEN3 throttle PIDs and airflow adder tables. 'Tis I that schooled YOU in that other thread.
Last edited by edcmat-l1; 09-08-2023 at 02:48 PM.
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This depends greatly on the engine design. Some engineers do not adequately calculate the temperature and velocity of gas in PCV hoses I think, or they do no long term testing or perhaps there isn't enough time. There is also the issue of oil as a gas state vs a conglomerate or liquid droplet. The droplet size and density of liquid oil contained with the PCV system is partially in response to pressure and flow, e.g. lower gas pressure and higher throughput PCV flow rates result with smaller and less density of oil droplet suspensions in the PCV flow. The hydrocarbons as a gas state will never be captured inside any kind of can; a catch can will not catch a gas, after all. These gas state hydrocarbons will always interact with the intake valves and ports and be able to condense and collect there depending on the temperature of the surface interaction. This is where I point out that a hot, high velocity PCV flow contains many hydrocarbon gas suspension molecules which will pass easily through the PCV hoses and return the cylinder from whence they came. The reason hydrocarbons condense and collect or accumulate into hoses and onto intake valves is because of temperature and velocity changes, either low temperature or sudden drop in pressure for example. A well designed PCV system will be able to maintain those hydrocarbons (suspended oil hydrocarbon gas products) as a suspended density in some fluid volume where it will not collect appreciably to cause any problem on the intake valves.
PCV is... a difficult topic. There is a right way to go about it, but depending on the engine the 'right way' is different, I think.
Interesting topic nontheless.
You didn't school anybody lmao. All you did was admit you don't know how to use a PID controller and have no control theory background. You found a work around for this deficiency and I didn't respond because I felt bad for you.
Still do. I like people, I Like flaws. I think you are great. But you pretend to do this for a living whereas I am a cancer researcher for my day job. So we have alternative goals. You need to be accepted as some kind of expert. I do not nor should I be able to care what people think.