Weber Emulsion Tube Tuning
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- swatson454
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Weber Emulsion Tube Tuning
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Postby swatson454 »
This forum obviously had some sharp guys on it so I'll post up my question.
How much effect do the emulsion tubes have on the air/fuel ratio at say a 2,000 rpm, lean-cruise scenario when that rpm is right about the tip-in point of the auxillary venturi?
I'm running a 38 DGS with a 150 main, 180 air corrector, and F50 emulsion tube combo and most of my cruise speed is at 2,000 rpm. With this combo, the main jets are beginning to flow and my air/fuel ratio drops to roughly 13.5:1, which I hardly consider a "lean-cruise" ratio. By raising the float level up, the ratio stays in the mid 14s but the activation of the main circuit is delayed enough to cause a lean hole when I go WOT at that engine speed. Is a different emulsion tube the correction here?
Thanks
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- technicaltom
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Re: Weber Emulsion Tube Tuning
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Postby technicaltom »
http://www.teglerizer.com/dcoe/inglese/ ... tuning.htm Hi this link may help you,If nothing else it very clearly describes Weber s workings.
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- Troy Patterson
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Re: Weber Emulsion Tube Tuning
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Postby Troy Patterson »
swatson454 wrote:This forum obviously had some sharp guys on it so I'll post up my question.
How much effect do the emulsion tubes have on the air/fuel ratio at say a 2,000 rpm, lean-cruise scenario when that rpm is right about the tip-in point of the auxillary venturi?
I'm running a 38 DGS with a 150 main, 180 air corrector, and F50 emulsion tube combo and most of my cruise speed is at 2,000 rpm. With this combo, the main jets are beginning to flow and my air/fuel ratio drops to roughly 13.5:1, which I hardly consider a "lean-cruise" ratio. By raising the float level up, the ratio stays in the mid 14s but the activation of the main circuit is delayed enough to cause a lean hole when I go WOT at that engine speed. Is a different emulsion tube the correction here?
Thanks
First of all, raising the float level will not "delay" activation of the main circuit. Raising the float level will bring the main circuit in earlier and perhaps a little richer. What you've written is confusing. By your description, it seems you are lowering the float level.
The emulsion tube is part of the main circuit, if when your main circuit is activated the air / fuel mixture changes, then clearly the emulsion tube is one of several factors affecting. The other factors are main jet, main air bleed (high speed in Holley talk) and the emulsion tubes (emulsion well and bleeds). I don't use F-50s, but from what I can tell about the F-50 is designed to provide a lean entry and delay the activation point of the main circuit. If you feel you need to enrich the activation or entry point of the main circuit, by all means try a different emulsion tube, a smaller main air corrector, main jet or raise the float.
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- swatson454
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Re: Weber Emulsion Tube Tuning
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Postby swatson454 »
Troy Patterson wrote:First of all, raising the float level will not "delay" activation of the main circuit. Raising the float level will bring the main circuit in earlier and perhaps a little richer. What you've written is confusing. By your description, it seems you are lowering the float level.Troy Patterson TMPCarbs.net TMP Carbs
You're right, I wrote that completey bass-ackwards. What I meant to say was that I increased the float drop, which would lower the fuel level in the well. My opologies.
My main jet/air corrector combo holds the fuel curve pretty darn flat at 12.9:1 from 2,500 rpm to 4,200 rpm redline. I'm just having a hard time putting my finger on the 13.5:1 lean cruise without going back to a pretty lean, 50 idle jet; which caused some lean conditions under a moderate acceleration before the main venturi began to flow.
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- Troy Patterson
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Re: Weber Emulsion Tube Tuning
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Postby Troy Patterson »
Are you certain you are only on the off-idle circuit at that cruise rpm?
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- swatson454
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Re: Weber Emulsion Tube Tuning
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Postby swatson454 »
Troy Patterson wrote:Are you certain you are only on the off-idle circuit at that cruise rpm?
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2,000 rpm is the point at which my main circuit begins to draw fuel under a moderate throttle position. Using a wide-band monitor, I can run up in rpm with a steady increase and clearly see a drop in the a/f ratio at 2,000 rpm. To double check what I thought I was looking at, I lowered the fuel level in the bowl and ran the test again. I got the same jump in the ratio but it happened at 2,300 rpm instead of the original 2,000 rpm so I concluded that that was the point of main curcuit 'tip in'.
What I've yet to learn is how much metering effect does the emulsion tube provide at that point without being at WOT.
Thanks for your replies
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- Troy Patterson
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Re: Weber Emulsion Tube Tuning
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Postby Troy Patterson »
Why do you keep messing with the float level when it's the main circuit you are interested in knowing something about? Raising or lowering the float level will only tell you what effect float level has.
How do you determine what a circuit or map is doing at any given point? Trial and error regardless of the metering type or manner the fuel is delivered. Change the main air corrector, jet or emulsion tube and take note of what impact that has on a / f ratio, drive-ability and so forth.
Also, if there is any load on the engine it will affect when the main circuit is activated relative to free reving the engine.
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- swatson454
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Re: Weber Emulsion Tube Tuning
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Postby swatson454 »
I only moved the float to validate what I was looking at and moved it back.
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- Troy Patterson
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Re: Weber Emulsion Tube Tuning
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Postby Troy Patterson »
Alright, do what I suggested and let us know what you find.
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- swatson454
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Re: Weber Emulsion Tube Tuning
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Postby swatson454 »
Troy Patterson wrote:Alright, do what I suggested and let us know what you find.
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Well that's just it. When it comes to tweaking the main jets and air correctors at WOT, I know exactly what to do and why. But for this particular issue, emulsion tube selection for part-throttle ratios, I don't have the foggiest idea where to start.
Do I need more holes, fewer holes, same holes but different position, different size hole on top? I just don't know where to start or why.
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MadBill
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Re: Weber Emulsion Tube Tuning
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Postby MadBill »
As a very approximate rule, more holes higher on the the emulsion tube leans out the early part of the transition. Holes lower down add air later in the transition. The alpha-numeric numbering system bears no relationship to the tube's characteristics.
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- Troy Patterson
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Re: Weber Emulsion Tube Tuning
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Postby Troy Patterson »
swatson454 wrote:
Troy Patterson wrote:Alright, do what I suggested and let us know what you find.
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Well that's just it. When it comes to tweaking the main jets and air correctors at WOT, I know exactly what to do and why. But for this particular issue, emulsion tube selection for part-throttle ratios, I don't have the foggiest idea where to start.
Do I need more holes, fewer holes, same holes but different position, different size hole on top? I just don't know where to start or why.
Okay, so you believe you have a lean stumble into the main circuit, correct? Question; is the main jet and air corrector optimized already for WOT throttle?
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- TRN
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Re: Weber Emulsion Tube Tuning
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Postby TRN »
Troy -
I believe the OP says there's a problem with being rich at cruising conditions, and the fuel curve is good for all WOT conditions.
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- Troy Patterson
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Re: Weber Emulsion Tube Tuning
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Postby Troy Patterson »
TRN wrote:Troy -
I believe the OP says there's a problem with being rich at cruising conditions, and the fuel curve is good for all WOT conditions.
I am wondering if he's taken the time to really work out WOT tuning or if we can alter the main jet and air corrector for tuning this portion of the fuel curve. If he feels WOT is optimized, then we'd want to address the emulsion tube and / or the off-idle circuitry. Just trying to gather meaningful information to work with.
The emulsion tubes has a lot of impact on the entry point and air / fuel ratio (at entry and beyond) of the main circuit. Assuming the main jet and air correctors are optimized for WOT, he should next try a different emulsion tube having fewer holes at or near the top of the emulsion tube.
Al alternate approach is not to assume he's nailed WOT calibration and reduce the size of the main air corrector and or increase the size of the main jet and see how it performs across the rpm range then. I really need a little more information to make well educated recommendations. It may be as simple as an emulsion tube change, but I have no reason to assume the main jet or air corrector is tuned as he's not said that, only that he is good at it. Big difference and I don't make like to make assumptions. His idea of well tuned and my idea may not be the same thing.
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- swatson454
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Re: Weber Emulsion Tube Tuning
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Postby swatson454 »
I've tested all mannor of main jet/air corrector combinations and am pretty darn certain that my combination is good. Like I said, the fuel curve stays flat at 12.9:1 at WOT from 2,500 rpm up to redline. I'd like it to be a touch richer but I'd have to enlarge a 175 air corrector to something smaller than the 180 I have now and I just haven't bothered to do it yet.
The emulsion tube is the only thing I haven't touched and it's because I don't know what to do with the damn thing. I'd sure like to be able to pull some of the excess fuel out of it at part-throttle cruise. For all I know, the emulsion tube isn't what I need to be focusing on and I'm overlooking something else. That's why I'm asking.
Things seem backwards. I have a rich part-throttle cruise but it goes lean when I go to WOT regardless of accelerator jet size until the main circuit seems to stabilize. This has happened regardless of main jet/air corrector combination, float setting or accelerator jet size. The only thing left is the emulsion tube, no? I'm missing something here.
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