Is the stock fresh air line that goes from the pass. valve cover to the TB enough for a street engine that makes pretty good power and sees high rpm? Or do I need breathers on each valve cover with a bigger diameter hole to make sure it's enough air? I still have the stock PCV valve installed with an oil separator between it and the port on the front of the intake.

With the stock PCV system still intact, the engine is drawing in fresh air from the TB to the valve cover, correct? Or does the air ever flow from the valve cover towards the TB?

 

yes, it flows from the passenger side of the TB to the valve cover through lifter valley out the PCV and back in to the intake under the TB. if you put breathers on the valve covers without capping off/deleting the entire PCV system then you will have unmetered air entering the intake AKA vacuum leak. shbox has some illustrations of this.

 

Should have mentioned, car will be tuned for speed density so I'm not running a MAF. Un-metered air isn't an issue.

 

but you still have a MAP sensor

 

I'm no expert so I'm sorry if I'm way off base, but I'm not seeing how introducing new air from the PCV into the intake wouldn't be picked up by the MAP sensor. It's taking a pressure reading of the air in the intake, which if I'm not missing something, wouldn't that include the PCV's air?

 

try drinking through a straw with a hole in the side. then read this
http://www.aa1car.com/library/map_sensors.htm

it is why i said delete and cap off the entire PCV to run vlve cover breathers or do not delete anything

 

From your link:

"Another advantage of speed-density EFI systems is that they are less sensitive to vacuum leaks. Any air that leaks into an engine on the back side an airflow sensor is "un-metered" air and really messes up the fine balance that's needed to maintain an accurate air/fuel mixture. In a speed-density system, the MAP sensor will detect the slight drop in vacuum caused by the air leak and the computer will compensate by adding more fuel."

Just to be clear, since this is primarily a street car I'd rather run the factory clean air hose if there's no problem in doing so. It just seems a lot of guys run breathers in place of that hose once they start getting into high-hp, high-rpm combos.

 

You can get a cheap evac system that ties into each side of the exhaust, that's what I plan on running.

Better then plain old breathers, and wont recirculate oily air like a PCV system.

 

I still have the PCV valve with an oil separator, it's just a matter of where the system is getting its fresh air from. I looked into the evac system but I'll be running a full exhaust on the car so it supposedly won't work well.

I guess all I really want to know is at what point are the factory PCV components not enough to adequately manage crankcase pressure. Being a street car though, a vacuum pump will never happen.

 

I'm running the stock PCV system. It does ingest oil, but no more than when it did stock. I blame the crap design of the baffle on the stock valve covers which I still run.

 

I run a breather to help keep oil out of the manifold, and the stock pcv system on the other side going into a catch can. The PCM can easily deal with the tiny amount of unmetered air going through on maf cars and on speed density it will be a non issue. The only reason I didn't delete the PCV system all together was to keep the engine bay from being coated in an oil mist.

 

Why would you get oil in the intake from the clean air tube though? Isn't the air supposed to be flowing from the TB into the valve cover, not the other way around? The oil separator on the PCV valve pipe is what would prevent oil from entering the intake, no?

If oil actually does make it back into the intake through that tube somehow that is definitely a good case for going to breathers, provided that it doesn't cover the engine bay in oil since it's apparently trying to leave through the breathers.

 

It reverses under higher load/higher throttle. The PCV valve is very restrictive and only sucks air out when the engine is in a higher vacuum state with low blowby. Go full throttle with no vacuum and quite a bit of blowby and all the air will go out through the unrestricted 1/2" hose vs a 3/8 hose with a huge restriction in it.

 

Ok, fair enough. Maybe I'll run hoses from the valve covers to a breather tank then.

 

I had a breather cap on my drivers side valve cover and I also had some other leaks. I found the engine runs better and I have less issues with the breaks getting hard and loosing vacuum when sitting at a light or lower RPM's. It may have been more from the leaks instead of the breather but my problem is now resolved. It could also be in conjunction with my cam but, I am not an expert it is just my personal findings.