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Alcohol Carb Question

General engine tech -- Drag Racing to Circle Track

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n5ifi
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Re: Alcohol Carb Question

Post by n5ifi »

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n5ifi
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Re: Alcohol Carb Question

Post by n5ifi »

n5ifi wrote: Sun Nov 08, 2020 5:23 pm Image
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Ks Fats
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Re: Alcohol Carb Question

Post by Ks Fats »

Does your by-pass regulator have an internal by-pass jet; the ones I have experience with have both the vacuum port and an internal jet to control idle pressure. I do circle track e-85 and methanol (belt drive) so shift recovery is not an issue however, maintaining proper fuel pressure when having to lift suddenly and reapply the throttle is. The balance between the by-pass jet, vacuum on the diaphragm and spring pressure is critical for this. Offering this up as an FYI only; I tend toward larger needle seats and lower than the norm fuel pressures so exact numbers would be meaningless to your application. It appears from the photo that the hole for the signal is drilled offset from the shaft centerline and then slotted toward the butterfly picking up manifold vacuum; not sure how modulating this through the throttle shaft is advantageous since the signal strength is relative to throttle position anyway.
n5ifi
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Re: Alcohol Carb Question

Post by n5ifi »

Ks Fats wrote: Wed Nov 11, 2020 10:22 am Does your by-pass regulator have an internal by-pass jet; the ones I have experience with have both the vacuum port and an internal jet to control idle pressure. I do circle track e-85 and methanol (belt drive) so shift recovery is not an issue however, maintaining proper fuel pressure when having to lift suddenly and reapply the throttle is. The balance between the by-pass jet, vacuum on the diaphragm and spring pressure is critical for this. Offering this up as an FYI only; I tend toward larger needle seats and lower than the norm fuel pressures so exact numbers would be meaningless to your application. It appears from the photo that the hole for the signal is drilled offset from the shaft centerline and then slotted toward the butterfly picking up manifold vacuum; not sure how modulating this through the throttle shaft is advantageous since the signal strength is relative to throttle position anyway.
No but I'm not running my regulator the way others are.
I'm running a vacuum line from the regulator to the carb and bypassing fuel back into the fuel cell before it goes into the carb.

I was just trying to figure out exactly what was going on in the picture above so I could modify another carb.

I can just take this apart I suppose.
Ks Fats
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Re: Alcohol Carb Question

Post by Ks Fats »

In my world running a system as you are usually produced a middle of the corner stumble when the throttle was picked up; running the regulator on the rear of the log with a B/P jet cured it. You are correct in pulling the primary shaft; it will give you an idea relative to slot depth and width. Not saying what your builder has done is incorrect, it just appears to be a redundant addition to the system (and not commonly used). For me the use of the vacuum line is not necessary in most applications; engine size, h.p., carb, pump etc. dictate that. A Waterman pump on a 390 rwhp crate might need it where a open rule methanol engine does not. Keep all of your variables the same when you do your second system so you get a good comparison.
n5ifi
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Re: Alcohol Carb Question

Post by n5ifi »

Ks Fats wrote: Thu Nov 12, 2020 10:07 am In my world running a system as you are usually produced a middle of the corner stumble when the throttle was picked up; running the regulator on the rear of the log with a B/P jet cured it. You are correct in pulling the primary shaft; it will give you an idea relative to slot depth and width. Not saying what your builder has done is incorrect, it just appears to be a redundant addition to the system (and not commonly used). For me the use of the vacuum line is not necessary in most applications; engine size, h.p., carb, pump etc. dictate that. A Waterman pump on a 390 rwhp crate might need it where a open rule methanol engine does not. Keep all of your variables the same when you do your second system so you get a good comparison.
Right, well I may need to try that then. Cant hurt anything I suppose. It was Patrick at Pro Systems that did the mod on the carb and honestly its worked pretty good on my car. I had to mess with the carb tune some but the rest of the setup has worked well. It is kind of unconventional; which is why I wrote a book in the first post.
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