breather bypass

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eric huskey 2

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I did the breather bypass today! My main goal was to keep carbon buildup out of my intake. After the truck ran a few minutes it started to whistle. While driving down the road you could here it inside the truck. I removed the bypass and fixed it back. :(
 
I never had that problem. The K&N intake "whistles" anyway but it's not something I'm worried about, as long as it performs.
 
How would you get carbon in your intake? That hose is providing clean filtered air into the engine crankcase where it is metered into the intake via the PCV. The airflow is from the intake into the valve cover, not the other direction.



If you bypass the intake with the breather, the MAF sensor doesn't get the chance to account for that air and your engine will run too lean.
 
What did you use to cap the hole on the intake ?????



Todd Z
 
My st is a job 1 01'. I used a cone filter from advance auto like the one in the projects sections to plug in the valve cover. Then I caped the hole in the intake hose with a 5/8" plug.
 
If you bypass the intake with the breather, the MAF sensor doesn't get the chance to account for that air and your engine will run too lean.
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I've never had any indication of my engine running to lean (CEL, significant change in MPG) after adding this mod.
 
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The MAF is before the intake breather hose, so that air isn't part of the mix measured by the MAF.
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Right. Air flows through the MAF and then either flows into the throttle body or else flows into the valve cover.



If you bypass the valve cover breather, that air gets sucked in from the engine compartment through the bypass filter and not get accounted for by the MAF.
 
The air goes into the valve cover. The PCV valve on the other side of the engine sucks that air from the engine and dumps it on the bottom side of the intake plenum. Know where the "infamous cracked elbow" is? That is where the air that goes through that "breather bypass" mod ends up.



Any air that is taken AFTER the MAF sensor is metered. Anything before is not metered. If you put a filter on the breather, you are introducing unmetered air into your engine.



Will it cause a CEL? You betcha. Those that did the mod and have no CEL, the odds are that you have a chip or an X-Cal that will keep the CEL light from coming on.



I had a DPFE sensor fail and it only showed itself when I turned the chip off to go through smog testing.





Tom
 
Will it cause a CEL? You betcha. Those that did the mod and have no CEL, the odds are that you have a chip or an X-Cal that will keep the CEL light from coming on.
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Tom,



I've had the breather bypass installed for over three years now on a stock tune and never thrown a CEL that could be attributed to this mod. I've only recently (in the last 30 days) added a custom XCal tune from Torrie.



So I guess I've beaten the odds. Perhaps I should play the lottery or go to Vegas, eh?:D
 
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Maybe it isn't enough to cause a CEL. Either way, if you look at the PCV plumbing, you will see that the breather bypass has air coming from the intake tube into the engine, then out of the engine into the intake past the throttle body.



It is your vehicle and not mine.





Tom
 
now that were on this topic lol.....r u guys talking about the hole on the intake that needs to have a filter on it, or that little hole on the left side of the engine?i have a little hole that looks like it should have a filter on it. its a hole on the left side of the engine block like on the left of the valve cover. does that need to be filtered air going in there?
 
You guys are running lean with the extra unmetered air. I'll bet your mod is costing you at least 5 horsepower or more, and your engines are running way closer to detonation.



Agree with Caymen, its your Trac, so have fun.
 
If we are referring to the tube running to the air intake being removed and replaced with a filter at the valve cover and a plug on the snorkel end as the "breather bypass", then I have the following comments. The valve cover needs to be vented to allow blow by gases to vent from the engine. otherwise you will build up pressure in the crank case. Vent gases travel FROM the valve cover TO the air intake prior to the MAF. By letting the valve cover to vent to the atmosphere rather than get sucked back into the intake will prevent carbon and oil rich gases from entering the intake side of the engine. Newer engines have very little oil bypass but with mileage age this will increase. This mod should have no affect on the MAF sensors ability to measure air flow. No CEL should be thrown that is attributed to this mod. If a CEL is being thrown it is for some other reason.
 
Vent gases travel FROM the valve cover TO the air intake prior to the MAF.
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Wrong.



This tube supplies the fresh clean air to the engine crankcase through the valve cover. Vent gases from the crankcase travel up to the opposite valve cover and then through the PVC valve and then into the engine intake to be burned. This aire needs to be metered and accounted for to ensure proper air/fuel mixture.
 
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Thinking out loud. The crankcase sees the blow by gases. The PVC vents gases from the one valve cover into the intake manifold. This valve cover gets the gases via the oil hole galleys in the head and block. So does the other valve cover. The other valve cover is attached to the intake to be of the engine which will cause a low pressure at the coupling tube via the Bernoulli affect. This low pressure should "suck" the gases from the cover. I'm opened minded so which of these are wrong?



These filters placed on the valve covers are referred to as "vent filters" not inlet filters. Where is the vacuum coming from the valve cover that allows the cover to suck in fresh air. It sees the same pressure as the oil pan. I believe that both valve covers are "vented" and one is not an air inlet to the engine. The metering problem you refer to is the the PVC vented gases are directly put into the manifold and are NOT accounted for by the MAF sensor.
 
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These filters placed on the valve covers are referred to as "vent filters" not inlet filters. Where is the vacuum coming from the valve cover that allows the cover to suck in fresh air. It sees the same pressure as the oil pan. I believe that both valve covers are "vented" and one is not an air inlet to the engine. The metering problem you refer to is the the PVC vented gases are directly put into the manifold and are NOT accounted for by the MAF sensor.
Click to expand...



You are wrong, plain and simple.





Tom
 

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