ORIGINAL: beau0090_99
I think this subject is going a little beyond what the original intent was for, but I am curious about this subject. Bruce, I understand what you are saying about the throttle being almost fully open (probably around 90%) effective area when the barrel is rotated only roughly 65% on most engines, but what is there to say about the spray bar? I am under the impression that as the throttle rotates, the needle and seat move in relation to each other creating a larger orifice when open. Does 90% of this get accomplished by the time the barrel is rotated 65% or so?
Just curious,
Curtis
This would depend on the exact design of the carb. But YES, I think it would in most cases. I have no empirical proof of this however. With more air you need more fuel, this much is obvious. And then you adjust the HS needle for fine tuning. Most carbs have HS and LS adjustments for mixture but there are a few with mid-range needles/adjustments. I do not recall the brands at this time. The slope/angle of the groove (cam effect) in the barrel controls the rate of change in the needle to spraybar spacing and the mfg could tune midrange some through that.