Hi-speed/Lean out question

Discussion in 'PSI Superchargers Tech Questions' started by Comax Racing, Oct 26, 2012.

  1. Comax Racing

    Comax Racing Member

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    I have a question about the use of high speed/lean outs and electic lean outs (staging). This is just a hypothetical question for now. If your jet software tells you you need a total jet area of say .016513 (145 main jet) for proper A/F ratio, do all your lean outs (pump loop/hi speed and say a stage valve) have to add together to yield the .016513" jet area? The one that is confusing me the most is the stage valve because its only flowing at staging and not any other time down track so if it its jet is included in the fuel system as a whole won't that cause everything to be too rich? Should a stage valve not be included in the scheme of the fuel system for this reason and just lean the engine a bit at the beginning and thats it?

    I realize this is a (perfect storm) question and there are lots of variable but theoretically is this the case, or is this how you basically decide on your jet sizes in various lean outs?

    Thanks
    Corey
     
    #1
    Last edited: Oct 26, 2012
    Comax Racing, Oct 26, 2012
  2. underby6

    underby6 Active Member

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    If I'm understanding you correctly you have a valve for stage that only functions when the tb is pressed; once you release the tb the valve closes. In that case you wouldn't need to factor that jet into jetsize or similar program. Any other leanouts that will be on should be added to the program. You'll then need to change your modifier as you go to figure your optimal jetsize based on plug readings.

    Brandon Booher
    NHRA TAD #34
     
    #2
    underby6, Oct 26, 2012
  3. Comax Racing

    Comax Racing Member

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    I think I confused things when I said "jet software" to get your total jet area. Let me back up a bit and say for the time being we know the "optimum jet area" (how we found that out isn't important right at this point)

    You said that a stage valve for pulling fuel while on a 2 step won't be included in the total bypass jet area scheme, but all the rest of you lean outs should add up to your "optimum jet area". I think am starting to see now. I am just really bad a convey in writing what I'm thinking:eek: I am trying to keep these questions as simple as possible because there is a potential for this to get unnessisarily complicated.:D
     
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    Comax Racing, Oct 26, 2012
  4. secondwindracing

    secondwindracing top alcohol

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    let me get on the PA system ..att. in the pits Mike Canter please answer this question....
     
    #4
    secondwindracing, Oct 26, 2012
  5. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    jets

    Stage jet - it's just to get the stage flow correct. it's not part of the a/f calc for the run. basically a stage jet takes the place of the bv at stage when you are leaving WOT.

    Any jets that are open for the entire run should be figured into the jetsize, or whatever software you are using.

    If you have a jet controlled by a timer or gear shift, event, etc., personally I don't figure those into my main jet calculation in jet size. On my leanout timers I will use bigger or smaller jets as a tuning tool to control wheelspeed, not so much going for optimum A/F ratio.

    If you want to know how much fuel you have in a certain stage with a jet open, you can put those jets into the program, and it will give you the flow for that 'stage' of the run.

    To figure your main jet you just need to use the jets that are open the whole run. Usually those are your pump loop and high speeds that are only regulated by poppet pressure, not a valve.

    I'm sure there is different ways to skin the cat, but that is what works for me.
     
    #5
    Will Hanna, Oct 26, 2012
  6. Mike Canter

    Mike Canter Top Dragster
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    As what Will said but with a little more info. With Jetsize you pick either 8000 or 9000 rpm in a certain gear such as high gear. There are other ways that are used but will keep it the most used way. So let's say the Jetsize reference point is 8000 in high gear. You only use the bypasses that are turned on when at 8000 in high gear. If you are running the eighth mile and never get to 8000 or 9000 in high gear then chose 8000 or 9000 in second gear and then you only use the bypasses that are turrned on at that time. So that includes your pump loop but will NOT include staging only bypasses. If you have a fuel flow meter then you would see that the fuel flow and fuel pressure have to be adjusted in Jetsize with the bypass that are ON at that moment in time at that 8000 or 9000 rpm reference point. Does that make sense?
     
    #6
    Mike Canter, Oct 27, 2012
  7. Comax Racing

    Comax Racing Member

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    Yup, makes sense. One other question then, keeping all the info you and Will provided in mind, when choosing lean outs that are not "on" at your 8000(9000) is the best way to dial those in to just put in a conservative size bypass jet and sneak up on it using et and MPH as a basis? I imagine it would be hard to use plugs as a tuning tool on bypasses that are not on at high RPM because the plugs will only show your 8000(9000) rpm tuneup? I guess a person could watch 60ft's when tuning a staging lean out.

    Thanks this stuff is slowing starting to sink in.

    Corey
     
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    Comax Racing, Oct 27, 2012

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