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Function of Weber Air Corrector Explained

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The main jet, emulsion tube and Air corrector all must hold hands in order for the main circuit of the car to act as it should and when it should. Understanding the function of each part is critical to being able to tune the car. Blue has done so many great explanations of carbs, interiors, etc that I thought I would try to add to some of the core knowledge on the board. I am by no means an expert, but at times, I have been told I can explain things in a very easy to understand manner.

So lets talk about the air corrector on Webers (or Mikuni's I guess as well). The air corrector allows air to come into contact with the fuel coming form the main jet and then enter the primary circuit to feed the engine along with the idle circuit.


You can see the air as shown by the little white arrow coming in through the Air corrector, and then into the Emulsion Tube where it is mixed with the fuel that is pulled up (via engine vacuum) through the main jet. The air and the fuel are mixed together in the E-tube. That is a whole other science in itself, and I will not attempt to explain which E tube is best for you. There are books written on that alone!

So back to the Air corrector. It sees atmospheric pressure. So how can I relate the function of the Air correcter? Well how about this. Ever try to drink a beverage with a straw that is cracked?

Lets break it down even more.

You are the engine.

You suck on the straw providing vacuum to the straw

Normally, if the straw was solid (Air corrector of Zero) you would raise the beverage to your mouth (primary circuit) with ease - However this is a highly undesirable situation to dump raw fuel into the engine. The job of the carburetor is to mix fuel and air, not dump a stream of gasoline into the intake manifold.

So Same situation:

You are the engine

You suck on the straw providing vacuum to the straw

This time the straw has a crack in it right below your lips. So the constant engine vacuum still pulls on the liquid surface but you lose some through the crack. You can raise the liquid level to your lips but is harder to raise it to that level. And when the liquid gets to the crack in the straw you entrain some air into the liquid stream so you get mixture of liquid and air. A air correcter is born.

The size of the crack is the air corrector. The larger the number on your Air corrector (the larger the crack), the more air comes in and less fuel, AND the harder it is to raise the fuel in the straw. This can lead to a lean air fuel mixture

Lets look at it again with this diagram:


Again, the engine is providing a fixed amount of vacuum. The main jet is busy acting as an orifice controlling the flowrate into the Emulsion tube.

The Air corrector acts as a vacuum bleed of sorts. The larger the AC, the more air you will get and the harder it will be to raise the liquid level up the E tube. (This is also why it is so critical to get the float level right, as if the fuel level is low, then the engine has to raise the level more before it gets any gas)

Hope this helps explain in a very basic manner how the Air correcter works. IF there are any errors, please point them out and we can get some more great info on this website.

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That is great high level explanation. I wish I could add more of the details but I am still lost:

Here are other parts of the main circuit to address:

  • "bubbles" The emulsion tube causes the fuel to bubble and flow in a different fashion from a liquid or a gas
  • fuel drop in the main circuit well. As the fuel draw increases, venturi pull on the gas and air from the main circuit increases causing fuel level to drop in the well
  • emulsion tube resistance to air and fuel flow. The physical design of the tube (gap to well wall, as well as all of the holes(dia, qty,location) all play a part
  • dynamics of fuel drop, wet to dry hole exposure, short circuiting of air correction flow and other interesting things all play a factor in the main circuit

And on top of this, the accelerator circuit is leaking

This is all too complex for my little brain thus I am now in the trial and error camp

Edited by Blue
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Totally agree there is much left on the table to learn about

but going in too deep becomes a parametric discussion on too many variables

I just wanted to give people a brief description of what happens when you decide to turn the Air Corrector knob up or down.

I find emulsion tubes fascinating, and I bet they were derived more from experiment than calculations

Every little bit of knowledge helps us. It is important to get the high level theory right first

Happy tuning

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