Has anyone removed their PCV hose to the intake and put a breather in?

[Cobra123089]

This is actually a pretty sizeable vacuum leak.

In the OE setup, the source of air for the driver's side VC comes from the intake duct, after the MAF. As you note, air enters the driver's side VC, passes through the crankcase and is pulled into the plenum. Again, in the OE setup, this air is accounted for by the MAF. In your setup though, the air is being pulled from under the hood and the MAF doesn't know about it. This isn't the equivalent of a small pinhole or crack in a vacuum line: All the PCV hoses are fairly sizable.



You probably won't notice it at idle since the PCV valve is basically closed then. If the valve did stick, you'd probably have a crazy idle since you'd be getting unmetered air bypassing the IAC valve and throttle body. At part-throttle cruise, when the PCV is open, the PCM is probably just compensating with fuel trims when in closed loop. It would be interesting to see the ST and LTFTs out of curiosity.

At WOT, it is technically a vacuum leak but the volume of air entering the engine past the wide-open throttle body probably swamps whatever the PCV is contributing. As well, since you're feeding to the plenum, at WOT there's not a lot of vacuum there anyway so the amount of unmetered air is fairly small.

So it's really at part-throttle that this becomes a concern. If the leak isn't too bad the PCM will just adjust for it. Still... it is a vacuum leak

I dont see how its a vacuum leak. The air never enters the combustion chamber therefore it can not affect a/f ratios. I understand that the stock PCV vents after the maf in the intake tube, but that air/oil should not have o2 in it. maybe you can explain better.

 

[BrightBlue00GT]

Breathers are not for daily drivers. You will get fumes in your car wich would be just like sucking on your tail pipe. Leave your PVC system as is or replace w/a couple of catch cans running hoses from each of the valve covers (Remove the PVC valve and replace w/the right size spout). The engine will force the fumes/blowby through the hoses w/crank case pressure.
Cap off your vacuum running from the bottom of the upper intake. Its way too strong for engine. (In my opinion a Ford desighn flaw) You will suck fresh oil in your intake, thus lowering your octane levels. The vacuum will force the oil off of your bearings and to the sides of your engine, thus starving your topend of fresh oil, yes the vacuum there is that strong.
Use the side of the "Cold air intake" thats below the IAC nozzle to vent the gasses. Breathers are a bad idea all together if you drive your stang daily, the smell is horrendous, yes, stronger then the deisel engines. Yuck.

Thanks Trom. Do you have or know where I can find some photos of a PVC-less catch can setup as you describe?

 

[trombonedemon]

Thanks Trom. Do you have or know where I can find some photos of a PVC-less catch can setup as you describe?

My digital camera is funky right now, but this is a simple thing to setup.
Your best price on catch cans is on ebay and some high pressure hoses should be fine, 3/8's, all of the hardware can be found at lowes, you can put the cans below the coolant/degas bottle with a large hose clamp. You won't have to worry about the hoses colapsing b/c there is no vacuum.