i understand the venture effect. however, I do not understand how air and any liquid can be compared physically, I digress. nonetheless, set up a venturi tube and force your choice of content through it. poke a hole in it. it's going to leak...


I've had numerous cars with exhaust leaks before the o2. those same cars had wideband o2 sensors on them. none of the exhaust leaks altered the afr. a gaping hole pre-o2, yeah that'll cause a problem. something the size of that crack in your header...? no.

Exhaust Manifold: Stock vs Headers for MPG
 

When it refers to the way things flow gases and liquids behave identically which is why they are called fluids.

Did you see the video?

yeah, I saw the video. I understand the scavenging qualities of a header collector, vacuum effect, etc. I'm arguing that a crack in the manifold is going to cause a rich condition as described.


edit: one thing that video is failing to acknowledge is backpressure and exhaust pulses. not only could I see carbon around the crack in the manifold, I could also feel the exhaust exiting with my finger. not to mention, my primaries on my stock header showed signs of being hot and 4 of the 6 plugs have looked a bit lean with or without the crack in the manifold.

Exhaust Manifold: Stock vs Headers for MPG
 

Gas is a fluid. You can't argue or disagree with this. Whether you understand it or not does not change physics.

Negative pressure at a crack does not always happen. Just because the stars aren't always aligned for it to happen doesn't change the fact that it can and does happen.

Exhaust Manifold: Stock vs Headers for MPG
 

Thank you.

my jeep defies physics. it should be in a museum.

Exhaust Manifold: Stock vs Headers for MPG
 

It doesn't defy physics. The cracks just not in the right spot.

Honestly, there are many possible factors controlling why yours may not be having an issue including where the crack is in relation to the sensors, however the issue of a cracked manifold sucking in air and throwing off the sensor really isn't debatable. Its a common occurrence and easily repeatable.

Wow.
You do realize that metal expands when heated , right? Heh, this is a topic that's been covered & validated for ,like,ever ? A cracked manifold does suck air in as it expands ....it can expell the same type of air that appears to flow plentifully between your ears ,as well....
:icon_confused:


Srry to butt-in ,but as I read this reply I just..... sheez.....

0

are you implying an exhaust leak will get larger as the parts warm up?

:popcorn: :popcorn:

Move over Fred. I gotta watch this too.

You boys move to the corners so I can plop down in the middle, there's plenty of room on this couch :brickwall:

Screw studying for finals...I'm going to sit back and learn all I need right here.