grygst76,

I'm not sure how to respond to your last post because, I'll admit, I'm not getting your point. The purpose of the MAF is to measure all air entering the combustion chamber. The IAC air, the PCV air, and the air that passes through the throttle plates has all been measured by the MAF, since the MAF is between those items and the source of air (the air filter). If the MAF is circumvented by installing a valvecover breather, thereby creating an inlet for air to ENTER the combustion chamber without passing through the MAF, a vacuum leak has been created.

Just a thought on what the misunderstanding may be:
Realize that the air flows thorugh the MAF (meaning it's been measured by the MAF), through the top of the throttle body, to the passenger side valve cover, through the crankcase, to the PCV valve on the driver side of the engine. From there it flows to the idle air passage in the intake manifold itself, not back to the throttle body or the intake ducting:

AIR FILTER->MAF->top of TB->valvecover->crankcase->PVC valve->intake manifold->combustion chamber

If you installed a valvecover breather, air would enter at the "valvecover" step and continue to the combustion chamber, bot not be measured by the MAF.

Rob
95Z28

 

Part of the air that went through the MAF sensor was rerouted to the PCV system (that is the air we are talking about...it originated from the same batch of air) it then goes through the line back into the throttle body....again....that is how it is metered air. It goes through the throttlebody TWICE...this isn't some new mass of air.

Joe

 

Guys one thing I want you to know..

There are guys who really know their stuff on this website.

I can understand if someone do not believe the other ones explanation or it does not make sense at first glance. I for one dont know jack about engines when compared to the likes of Shoebox or Injuneer. Now let me be clear that I am not trying to Kiss their royal behinds... They are good at what they know and if they say the friggin sky is not blue I will not contest them unless I have some cientific evidence that what they say its not
true...

I understood Injuneers explanations on the first try... all the air comes in through the MAF and afterwards it can be re-routed 90 times past the throttle plates for all I care... it has already been acounted for... If I can understand it with my only two brain cells left in my empty head I am sure all of you can do it too..

I like to type a lot and tend to be very redundant when I type so hate me all if you want... What I am going to say is that
I respect those guys plus every other guy who knows his stuff and I am calling out to you guys to give them a break.

This guys know their stuff and are willing to share their knowledge with us and for free.... yeah thats right. I dont know of anyone who pays them to asnwer our dumb azz questions.

So Thank you Injuneer and Shoebox. I am not kissing your .... you know what.. I am honestly thanking your for participating in this website that is a goldmine in itself and I for one know what I know (however little it maybe) from listening and paying attention to your posts..

I understood your explanations they were very clear ....

Thanks again.

Marvin

 

Sure, the pcm uses the MAF info. What you (or even the book) are leaving out is that is not the only input it uses to control fuel delivery. You may be taking that sentence in the book too literally.

Once the air passes through the MAF and is measured, it does not matter if some of the air goes through the pcv system or not. Now, if you put on a breather and don't suppress the vacuum to the pcv valve, then you are allowing unmetered air to enter the engine. As Fred stated, the pcm will make adjustments via what the O2 sensors see.

 

Hey guys Just a lil note......

My local Checkers Autoparts did not have neither one of the products on the shelves however by visual inspection I found their part number Fram BA6592 to look exactly as the one in the picture....

I purchased it for 4.99... its Hawaii you see ... I bet you guys can buy it for cheap in the Mainland... Anyway It does fit perfectly... its a 1 minute change over Mod.

And I know it could be just a Figment of my twisted imagination but the car feels better! I know I know... there is no way an inline filter can make this kind of difference and I kept telling myself... hey Mental.. you just imagining this stuff... and yet I kept hallucinating or somenthing but it does feel better.


Just to let you know... Part Number "FRAM BA6592. It keeps everything sealed just like OEM and yet it adds an inline filter.


Marvin

 

OK, this should end your confusion. It doesn't need to say 30 pounds (or whatever measurement is used) minus this for PCV, or minus that for anything else because ALL that air still makes it to the combustion chamber to be ignited, along with the air that went straight through the TB as normal. So, ALL the air passed through the MAF, and ALL the air made it to the combustion chamber, so all the air was metered. Got it?

 

How about a diagram?

 

look at the system as 2 parts-vapors within the crankcase are being withdrawn at varying rates, dictated by the manifold vacuum everchanging as you drive along. engine vacuum metered down via the pcv valve to whatever the engineers see fit for a particular engine combo. these vapors constitute a quantity (mass) of "air"that is being drawn into the combustion chambers. that is the first part. ok-the other part of the balanced system we are discussing would be the hose in question, the hose that started this thread-the breather hose-what would happen to the first part of the system. what if there was no way to replenish the atmosphere within the crankcase as the pcv(metered manifold vacuum)valve sucked it out? at the best case "nothing" after a while. so another line is installed with the sole purpose of allowing some "air" back in to keep the process flowing. the "breather" cuz it lets the motor breathe in fresh air prior to being mixed up with whatever combustion byproducts are in the motor and being sucked into the manifold and burned up. the "air" that flows into the motor is after the maf so it is accounted for as the pcm executes its code and makes its decisions. now-take the hose off the throttle body, plug the nipple, and stick a breather on the valve cover where the other end used to be-sure you still have "air" (crankcase vapors) being drawn into the manifold via the pcv-but now that mass of air is not being seen by the maf because it originated outside the loop, thru the new aftermarket open breather it was allowed into the crankcase . no longer is there a nice balance of in and out. kinda makes sense to invest in nice ac delco pcv valves when that time comes around. that oil in the breather line is because (usually) the blowby past the rings is outpacing the pcv's ability to withdraw it from the crankcase, what do you get? positive pressure-its gotta go somewhere-the breather line starts flowing opposite-exhaling-right into the t-body goes the crankcase vapors. hope this helped explain some.

 

Need to fix problem, need to understand it. I have oil showing in the top of the TB, comming from the passenger side valve cover. Bought a new pcv valve and went to replace it. The L shaped rubber hose at the pcv valve is ruptured. Once I replace that hose and install the new pcv valve, will my 97 LT1 stop sucking oil into the TB? If not, will installing one of the afore mentioned "filters" keep my pcv system intact and correct. You guys rule, inform me, enlighten me. Happy New Year!!! And if you really know your stuff, tell me what that ruptured hose was doing to my motor, I have some pretty serious oil leaks. down the back of the motor and from the low oil sensor, thanks

 

The PCV hose is U shaped, drivers side.
Replacing the L shaped hose[psgr side] won't stop oil from going into the throttle body.
The oil seperator will reduce oil into the throttle body.

 

You have to remember not all LT1's are the same. 93/94 use the U-shaped hose to route the PCV valve back into the intake manifold. 95 up routes that line to a fitting on the intake manifold under the throttle body. And.... there are a few various emissions setups that mix and match the two configurations

 

Wow This thread is long. I have read up on all these pcv system threads and Fred has been crystal clear on how this PCV works. But I do have one question... How does an airfoil affest this system. Because it seems like very little about of room is left in the passages for the pcv system. And I do get plenty of oil in that hose even with these oil seporators.

 

Well I did my PVC, inline filter and valve cover gaskets (psg side was leaking) and I am having the same hallucination. Seems to idle a bit smoother. Seems a bit more refined. I cleaned oil out of my TB a while back and noticed that it has not returned. w00t!

 

An airfoil shouldn't affect the PCV system. I have heard some reports of certain airfoils that, when installed, block the passages to the idle air circuit. Just be sure that whatever airfoil you choose will let air get past and to the idle air bleed hole in the TB.

FYI, the PCV gets vacuum from the idle air passage but it's a different port (below the idle air passage).

RobY
95Z28

 

Not so sure that statement is completely correct. The air supply (which is eventually pulled through the crankcase and out the PCV valve), to the line from the TB to the passenger side valve cover comes from the upper triangular space, in front of, and above the throttle blades. The hole is on the top of the triangular space, and opens directly into the chamber under the TB cover plate. It is conceivable that a poorly designed air foil could close that space off, and limit the air flow that sweeps vapors from the crankcase.