Quote: Originally Posted by letxen3
Its a bad idea to mess with the PCV system for several reasons.
1) The driving force for succesfully keeping the crankcase under a vacuum is very low. Adding a catch can into the path between the crank case and the throttle body increases these losses.
2) The engine management system actually accounts for some oil vapor coming into the intake. This is important because that oil vapor affects the overall octane of the air/fuel in the combustion chamber. (This is true of an EGR (Exhaust Gas Return Valve) when not under boost as well)
3) Failure to maintain a vacuum on the crankcase causes pressure to build on the wrong side of the piston rings. This can affect horsepower and in extreme cases impact the rings ability to seat properly. This in turn increases blowby and makes original problem of too little crankcase vacuum worse.
4) Ironically, for the PCV system to work as designed, it also relies on the restriction of the OEM air filter. Under boost, that restriction insures that the hose at the turbo inlet has vacuum to pull from the crankcase. But, eh, thats the first thing people mess with not realizing that they have affected the lifespan of the rings and increased the risk of leaky gaskets all over the engine.
Please read this information from answers.com.....
The PCV system consists of: 1) The breather tube , and 2) The PCV valve. The breather tube is just an open tube that connects the crankcase to a clean source of fresh air, such as the air cleaner body. The PCV valve connects the crankcase to the intake manifold from a location more-or-less opposite the breather connection. A typical location is the valve cover, although some engines place the valve in locations far from the valve cover.
Counter point to 1. If you install a catch can and notice a change in your idle as noted on your boost guage then yes it might make a difference. BUT, if you make sure there are no leaks then it doesn't make any difference. And what do you mean driving force.... like the vaccuum created by the air passing through the throtle body. Well yes that does change, all the time, as you drive.
Counter point 2. The EMS may take in consideration that there is shit air coming in, but that is why we TUNE our vehicles. Manufactures regularly make stock vehicles run on the side of rich anyway to keep them a little slow, more emission friendly and last longer. Soooooo, if by some chance running a little bit less filthy air into the combustion chamber makes our A/F ratio a little bit more lean, it might actually make the car run better. If any change I'm sure it's not signifigant. Dirty air is still getting in. By using a catch can, sludge that ends up in your intake path will not.
Counter point 3. Not too sure what you mean here. People probibly don't start doing anything with thier cas untill after the break in. In which case your seating of your rings won't be affected. The vaccuum isn't created by the crankcase, it is by the intake air. The only way the pressure would build and hurt anything is if your PCV valve was not working correctly and you let it go for a good period of time
Counter point 4. Your silly. That tube is a fresh air source only, which draws clean air in under normal drive or de-excel and actually vents during boost. It means nothing to have it on the intake or off the intake as long as it's clean air being drawn into the valve cover/crankcase.
I am sure all the people who race normal cars, or performance monsters will tell you all i have said is correct. They have been using breather filters and catch cans for many years now. Shit some rules mandate the use of these things.
