# A simple way of tuning with Emulsion Tubes.



## B4S (Apr 16, 2003)

Since I'm basically surplus at work, I have spent some time reading about emulsion tubes. I stumbled upon a really simple way of telling what tube does what, in a basic form. Since the tube essentially controls when the main circuit becomes active, and the curve of the fueling (the main air doesn't have as large of an effect as the etubes do), it's good to know how to tune the curve by tube, at a glance. This applies for pretty much all carbs out there, it's ridiculously simple:









NOTE: this is a highly simplified version of what an emulsion tube does, and does NOT take into account the steps in the tubes, or any of the Weber-specific angled drillings (like on the F16).


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## B4S (Apr 16, 2003)

As well, the pressures that exist in the jet 'well' are MUCH higher at WOT than they are at low RPM, so the size of the holes will vary. A large hole at the top (high RPM) could do the same thing as a small hole at the bottom (low RPM).

I know this is a part of carb tuning that doesn't really get much attention, but it can be very useful if you're hunting for the exact perfect jetting. Not too many folks do, but I'm sure there are a few others out there with the same problem as me .

Where I learned the trick:






David Vizard is quite simply, amazing :thumbup: .


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## B4S (Apr 16, 2003)

I'm bumping this up, cause I think it's neat .


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## notajetta (Nov 17, 2007)

subscribed so i can keep it in my "useful info" folder :thumbup:
thanks for this and all the other useful info you've posted! :beer:


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## B4S (Apr 16, 2003)

I'm not ashamed of my addiction :laugh: .

Until every set of carbs on the VWVortex is tuned properly, I'll keep posting :thumbup:.


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## impulse byer (Mar 8, 2003)

Great stuff as usual. Going to put my phone down and get on the desktop to make this easier lol


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## antichristonwheels (Jun 14, 2001)

I hate to question the wisdom of Vizard but how does RPM affect flow at different stages of the tube?


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## B4S (Apr 16, 2003)

To be honest, the fluid dynamics of it all escapes me. It helps me when I also think of the holes as 'brakes' for the fuel travelling up the tube/well towards the fuel feed to the venturi. At higher RPMs, the pressures in the well/tube are going to be much different than at cruise or part throttle, which could explain why the hole placement/size is so much more different at the top-end portion of the tube vs. the low. Not to forget that at WOT, the well is not holding fuel so much as directing it. At this point, the emulsion tube is purely for air from the corrector. The higher the RPMs, the lower the fuel level in the well, which exposes more holes from the emulsion tube, which in turn changes the fuel/air mix.

There is so much info out there about emulsion tubes, and it's all so contradictory. It's tough to tell what is truth and what is guess. The only consistent bit of info I've ever found has been the air-brake portion, so I've grasped on to that, lol. I found it meshed quite well with Vizard's ideas really well. It certainly helps paint a bit of a picture in my head in regards to the tubes I've played with over the years. My emissions carbs had 7772.10 tubes in them (they looked like swiss cheese), and behaved exactly like Vizard said. My current 7772.5 tubes have almost no holes in them, and again, work exactly like he described. On the .10s, it would be a steady lean-out at WOT, no matter what I did. With the .5s, it stays rock-steady, slowly richening about half a point from 4500ish-7000. My jetting is fairly similar between both sets of carbs that I have experience with, at least at the WOT area. 130-135 mains, and 200 airs.

I'm sure there are tons of theories out there that disprove Vizard's, but so far, his the one that makes the most sense to me.


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## B4S (Apr 16, 2003)

I've got some pages from a Weber tuning manual that I'm trying to post, but my work locks down photobucket uploads. Grrr.


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## B4S (Apr 16, 2003)




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## wantacaddybad (Jun 14, 2006)

Great info! Is there a pdf. of the weber tuning manual? You think you could send it to me in a pm?
That would be greatly appreciated if so.


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## B4S (Apr 16, 2003)

Unfortunately I haven't found it yet. Those three pages are screen grabs I pulled off google. That's all I've got.


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## impulse byer (Mar 8, 2003)

I feel a "rigth click save as" coming on lol


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## antichristonwheels (Jun 14, 2001)

I think it's all in this book:

http://www.amazon.com/Weber-Carbure...=sr_1_1?s=books&ie=UTF8&qid=1299554062&sr=1-1

not home or I would check


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## ALLGORIMSHOW (Jul 1, 2002)

I have this one and it does give some good info. Mainly rebuilding but it covers Weber and Dellorto.

http://www.amazon.com/Build-Power-Dellorto-Carburettors-Speedpro/dp/1903706750/ref=pd_sim_b_3


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## pigryder (Mar 6, 2009)

B4S :thumbup: 

Tons of info


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## Antikrist~86CGT~ (Mar 24, 2009)

B4S= the Vortex carb jesus!!! :thumbup::beer:


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## B4S (Apr 16, 2003)

Lol...thank you for the compliment . I just share what I find, so everyone can benefit. David Vizard is a genius with carbs


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