Educate me on oil and the PCV system

[oldhp]

electrolover, Yes racecars use this, its a one-way checkvalve, won't let exhaust or backfire go into valvecover/crankcase.
A street car could use a smaller type venturi system.

My Ram Hemi doesn't burn any oil that shows on dipstick, but it does collect oil mist/water vapor from engine in my catchcan.

 

[Clevy]

Originally Posted By: RamFan
Originally Posted By: mechtech2
Originally Posted By: Phishin
Originally Posted By: mechtech2
There is an oil separator/baffle so liquid oil is not sucked through.


In theory, but it does. Sometimes quite a bit of oil get sucked up. That's why people install catch-cans on this plumbing....to prevent excessive oil from being introducted into the intake.

The oil drops to the can, yet the gases continue on to the combustion chamber.


I use zero oil, yet my catch can needs frequent draining. Your theory is wrong.


How can you use zero oil while also needing to frequently drain your catch can?


The oil collected in a catch can is vapour. At most we might be talking in ounces here. Think that would be visible on the dip stick?

 

[RamFan]

Originally Posted By: Clevy
Originally Posted By: RamFan
Originally Posted By: mechtech2
Originally Posted By: Phishin

In theory, but it does. Sometimes quite a bit of oil get sucked up. That's why people install catch-cans on this plumbing....to prevent excessive oil from being introducted into the intake.

The oil drops to the can, yet the gases continue on to the combustion chamber.


I use zero oil, yet my catch can needs frequent draining. Your theory is wrong.



How can you use zero oil while also needing to frequently drain your catch can?


The oil collected in a catch can is vapour. At most we might be talking in ounces here. Think that would be visible on the dip stick?


Assuming a quart is needed from low to full lines on the dipstick, if 8 ounces were caught the dipstick should read only 3/4 of the reading area. The reason I ask is that my Charger uses oil and I've been thinking of installing one to replenish the crankcase versus replenishing with new oil.

 

[oldhp]

RamFan, You could do it the summer, but in cooler/winter temps you get alot of water vapor which makes oil look like light brown goo. For no more than 1qt used, I would top off with new oil.

 

[ueberooo]

Hey, by the way, where is the PCV on the volvo V70?? I'd meant to clean that out but wasn't able to find it after tracing all the tubes that might be candidates.

 

[SHOZ]

Hyundais use a check valve for the PCV valve. It will not allow any passage back into the crankcase. Very important when you use forced induction. But still my Accent uses the same PCV valve.

Ford on the new turbo ecoboost motors uses a integrated screen/trap that returns the blowby back into the crankcase instead of ingesting it in the motor. This is to combat the carbon build up on the dry valves due to the direct injection. They are having fuel dilution problems with the oil now too.

 

[INDYMAC]

I like this article about the PCV valve:

http://www.tegger.com/hondafaq/pcv-replace/

 

[SHOZ]

On my last car, a naturally aspirated Ford V8 I had a catch can, I called it a condensation can, mounted in the fenderwell area where it was cool. The can was sealed with a spring loaded check valve that opened at or above atmospheric pressure. I then sealed off the air cleaner hose and ran the crankcase under vacuum when the throttle was not wide open.

This kept about 10" Hg vacuum on the crankcase under normal operating conditions. When I went out of vacuum then the check valve would open up. This allowed any crankcase pressure to dump the can, or when the motor was off the valve opened. It worked great.

On my turbo car I have a can on both sides. They have to be separate as the pcv valve to intake manifold can be under pressure from the turbo. The pcv valve will stop air flow into the crankcase. The other side sees both a slight vacuum and a slight pressure build up at pressures above atmospheric. But it is just open both ways. Oil will flow out of the valve cover and you don't want this in the turbo or intercooler.

 

[KevGuy]

Originally Posted By: eljefino
Working PCV is far better, it keeps oil mist outside the engine down and supposedly helps the rings seal better.

In the old days they used a "road draft tube" which basically kept the middle of every lane on the freeways a nice black color and made it greasy in the rain.

PCV was one of the first emissions controls, circa 1962!


Interesting. I never heard of a road draft tube. Can you please tell more about them, including maintenance issues or other stories about them?

 

[electrolover]

Originally Posted By: KevGuy
Originally Posted By: eljefino
Working PCV is far better, it keeps oil mist outside the engine down and supposedly helps the rings seal better.

In the old days they used a "road draft tube" which basically kept the middle of every lane on the freeways a nice black color and made it greasy in the rain.

PCV was one of the first emissions controls, circa 1962!


Interesting. I never heard of a road draft tube. Can you please tell more about them, including maintenance issues or other stories about them?



Really? Back in the old days they just used a blow down tube that was hooked up to the valve cover and pointed down. It relieved air pressure. Although the pcv system was an emission thing it works a hundred times better because it pulls a slight vacuum on the crankcase.