Isn't the intake side of the OEM CCV box connected to the turbo intake side of the intake system and therefore the highest pressure in that part of the intake system would be atmospheric due to suction of the turbo intake? Only exception would be a backfire in the intake tract therefore possibly pressurizing the turbo intake side if the intake system briefly higher than atmospheric. Not understanding how the valve in the OEM CCV you are referring to closes under turbo boost if the pressure in the hose to the CCV from the intake is at or below atmospheric pressure. Seems like that valve in the CCV might be nothing more than a backfire prevention device like the old PCV valve on a 1969 Camaro V8. IOW, to prevent a crankcase explosion due to a backfire in the intake system.

EDIT: I think I answered my question. High blow-by conditions in the crankcase combined with low pressure on the turbo inlet side create a pressure differential that closes the valve in the OEM CCV that prevents blow-by from the crankcase getting into the turbo inlet side of the intake. I think I was misunderstanding the forcing function and pressure delta for closing the CCV valve.

 

It is "sucked" closed by the turbo. I have never heard of a pcv valve being used to prevent an explosion, can you tell me more about this?

 

Gas engines like typical Chevy or Ford have crankcase vapors that can achieve an explosive air/fuel ratio. In the unlikely event a backfire into the intake manifold occurs such as a burned intake valve igniting the explosive air/fuel mixture in the intake manifold (we are talking carburetor or maybe throttle body injected engines here) and there is no check valve (the PCV valve's only purpose is to be this check valve) in the crankcase ventilation hose running from the valve cover to the base of the throttle body, that backfire can belch into the crankcase through the hose and explode the gas vapor in the crankcase.

In my former life I did service work on Cooper-Bessemer V10 and V20 gigantic engines that pump natural gas across the USA. The V10 was called the W-330, rated at I think 10,000 HP, but may have been 8,500. Anyway, those engines were dual-fueled. Could run on diesel or natural gas. The rod caps weighed 600 lbs. I can stand up inside the cylinder bore. So you have an idea of the size. On the side of the crankcase there were "blowout doors", designed to hopefully allow crankcase pressure to gradually escape in the event something ignited an explosive mixture in the crankcase. These doors were about 2 feet wide and 5 feet tall. Also used to get in the crankcase to work on the internals. A senior service rep told me a story about a fatality where a crankcase explosion blew one of the doors off and a worker was in the path of debris and unfortunately was killed on the spot. So, explosive crankcase mixtures can occur in any size of engine and any ignition source must be mitigated.

Edit: forgot to say the blowout doors had "pop-off" spring loaded relief valves, 2 of them on each door about 10" in diameter, spring loaded. Obviously they don't always work because someone died. Also, FWIW, the W-330 and Z-330 (the V-20 engine) were both turbocharged and intercooled. They had dual turbos, one for each bank of the V cylinder config. A single turbo (water cooled) for the W-330 weighed 6,250 lbs by itself and had a 24" diameter impeller.

 

Interesting, the little research I have done on pcv valves and systems did not turn this info up, I did find the early systems were to put pressure on the crank case to prevent water intrusion on tank engines that were prone to submersion. It was added to cars for emissions in the early 60's to combat smog. I do not think both systems operated the same as they are for two different jobs. Thanks for the information.

 

Those monsters certainly put the size of our engines into perspective.

 

Yes sir. At one site in SE Iowa, some of the older tech single cylinder compressors were in a long building. They had long horizontal strokes, parallel with the floor of the building, the stroke being around 12 to 14 feet long if I recall correctly. I think maybe 30 of them would be running at a time, and when enough of them randomly managed to get synchronized such that their reciprocating mass was moving together or mostly together, the entire 3 acres or so of property would shake. I was sitting in a pickup truck eating lunch one day and noticed my drink in the cupholder was moving back and forth. Then I noticed the moving sensation like a gently rocking boat. I asked around and the old timers there pointed out how the entire property was shaking. That's a lot of mass. The building I was working in had three of the W-330 engines brand new and they weren't on line yet. I worked for Cooper-Bessemer the company that made the engines. The 330 in the name stands for the rated RPM, so all that HP is made at 330 RPM. The flywheel for the W-330 weighed 14,000 lbs.

 

there are a few YouTube videos by customers saying the internal filter does not catch anything.

 

Interesting... Thanks for sharing...

I'd imagine ONE causing the ground to shake around let ALONE 30 of them... WOW... Crazy stuff alright...