Emulsion tubes - how do they work/what do they do? Options

[Scott S]

The carbs for my 2.7 are the 40 IDTP 13C. I called PMO to get jet suggestions. While they were very specific on idles, main and a/c , I told them I already had F1 emulsions and they said "those will work". Thats fine - I trust them - and I plan on using them.
However, all of the charts and maunals I have been able to locate (including the webber book) list the F-26 or F-3.

I understand that a larger/smaller jet simply means getting more or less of what ever it is you are regulating. I dont quite get what the emusion tubes do and how. Can anyone throw me a laymans explanation?

Thanks!
Scott S

[pbanders]

See:

http://www.aircooled.net/gnrlsite/resource...les/jetting.htm

From the article:

Lastly, you have emulsion tubes to change "where" it's rich, lean, etc.

Emulsion Tubes: The Emulsion Tube mixes air from the air corrector jet with fuel from the main jet, and controls the mixture from the discharge nozzle at all engine speeds that the main jet is working! Basically, the Emulsion Tube changes the diameter and location of small holes in it's body. For Weber IDF carbs, the F7 or F11 is usually what you need. The F "series" has no rhyme nor reason to the numbering system, so you can't tell anything by the number unless you look it up! But, with these two examples, the F7 richens the mixture up at the bottom of the RPM range and under acceleration, while the F11 leans the mixture out on the top end a little bit, and is usually used (high RPMs) when you use air jets larger than 200.

See:

http://www.rhinoracing.com/yaw/carb_tuning.htm

From this article:

Emulsion Tubes
The air from the air bleeds enters the main circuit through the emulsion tube. The emulsion tube has a series of small holes from top to bottom, and it is through these holes that air enters the main circuit. At low engine speeds, when fuel demand is low, these holes are submerged in fuel, and so no air can flow through them. As engine speed increases, the fuel level in the float bowl drops, uncovering these holes, and allowing air from the bleeds to enter the main circuit, thus leaning the mixture. As the engine speed increases further, the fuel level in the float bowl continues to drop. This uncovers even more of the holes in the emulsion tube, which makes the air bleed have a greater effect on the mixture.