Question for Taffy

6 replies to this topic
  • mnelson78

Posted May 14, 2002 - 09:04 PM


why is it that as the PJ/PAJ combo gets smaller the ratio gets richer?

Here's an excel chart to illustrate my question:
Posted Image


[ May 14, 2002: Message edited by: mnelson78 ]

  • neWRiver

Posted May 14, 2002 - 09:50 PM


This is just a stab, but you are assuming that the numerical scales for the jet sizes are proportional with respect to their effect on the air/fuel mixture. My understanding is that the PJ/PAJ combinations you have listed result in the same mixture (with respect to each other). It seems to me that the jet "numbers" are probably based on some linear dimension (such as diameter). Such a measurement would not bear a direct linear relationship to the amount of air or fuel that flows through the jet.

  • Rich_in_Orlando

Posted May 14, 2002 - 10:43 AM


Matt, it looks like your A/F ratios are only that: numerical ratios based on the jet numbers. 48 ÷ 110 = 0.436, 45 ÷ 100 = 0.45, etc. Apples to oranges. Taffy, I think you hit the nail right on the head.

[ May 14, 2002: Message edited by: Rich in Orlando ]

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  • Taffy

Posted May 14, 2002 - 12:31 PM


i just went by feel. i understand how it works and leave others to do the formulas!!!


  • mnelson78

Posted May 14, 2002 - 12:42 PM


With the 35/45 combo the fuel opening and the air opening are almost the same size, but with 48/110 the opening for the air is almost twice as big as the fuel opening. This didn't strick anyone as strange? I'm not trying to insinuate that it doesn't work well as I'm sure it does, I'm just trying to find out why.


  • Rich_in_Orlando

Posted May 14, 2002 - 04:47 PM


Matt, your are assuming that if you measured the diameter of the hole in a 45 pilot jet and a 45 pilot air jet the measurements would be the same. Also, you are assuming that the characteristics of the circuit (fuel and air) are identical all the time. I'm not positive, but I don't think those assumptions are correct. If they are not correct, then the calculations you made are meaningless, just some trivia. Basically, I think you may be oversimplifying the equation.

  • Taffy

Posted May 14, 2002 - 09:30 PM


i've not checked but some jets go by size like the MAJ. this is 1.6mm=#160MAJ etc etc.

others go by the fuel they can pass or the air they can pass so you can check it out.

also you must understand what they do. the air jet has to be doing a certain speed to pick up the fuel and no way is this graph linear.

you need to work out the speed that air goes through a smaller PAJ and then you need to do a graph of how fuel reacts to this suction.

funnily enough, and this presumes that i've got the tests about right, your results MUST/SHOULD match my figures. in other words if they don't you have to go away until they do!!!

now thAT DOES MAKE ME :) :D :D



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