Fuel control and wheel speed

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by Bjs344, Jul 23, 2017.

  1. Bjs344

    Bjs344 Member

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    ive never used a lean out, only used timing for wheel speed, so maybe I'm out in left field, but I would like to try to add wheel speed at a certain point in low gear with a lean out. Based on flash vs fallback, and what my converter guy said (shouldn't be that much lower on flash) I'm assuming I have too much fuel early in the run.

    So, if I want to add wheel speed at .xx in, should I open the leanout at .xx -.1, .xx -.2,?? Would it tend to ramp in power or more like a light switch?

    Also, I'm thinking I should shoot for a little less than 10% flow change on the leanout. 15 gallon pump with an .081 main. Thoughts on a starting point?
     
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  2. Bjs344

    Bjs344 Member

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    Bad idea or what?
     
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  3. overkill69

    overkill69 Member

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    A smart guy told me this...produce power with the fuel system and manage it with timing. I've made pretty good runs with nothing but a main jet. I think timing is a lot more critical.
     
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  4. Torment

    Torment Member

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    If the .081 is safe you could try a .075 in the main and a .040 in the lean out then turn the lean out on for maybe 3sec on the front side of the track - for example from 1-4sec... see how it responds and go from there. Watch your plugs and time slip, and any other data acquisition you have. My 2 cents.
     
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  5. bob szabo

    bob szabo FC / altered

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  6. Bjs344

    Bjs344 Member

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    So you're saying if I lean it out up front i need to be fatter out back? I can see how that might make sense, but I would have the leanout open for less than 1 second max. Just trying to keep it up on the tire about 0.5 sec longer.
     
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  7. jay70cuda

    jay70cuda Member

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    Open a jet all the way thru low gear. Close it at the shift. Everyone says you can't burn one up in low gear. If your safe thru the end of the run now it shouldn't effect it after the shift. Pumps run off psi. So your in the rpm range at the shift making peak pump psi. You'll have the same pump psi after the shift
     
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  8. bob szabo

    bob szabo FC / altered

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    The size of the main bypass also depends on the air density. Those sizes may work at one AD and need bumping at other ADs.

    Bob Szabo
    bob@racecarbook.com
     
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  9. Bjs344

    Bjs344 Member

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    Bob, not entirely true. 81 pill stays in from 1400' to 4000'.

    Using the lean out to add wheel speed wasn't the worst idea ever. 3 fastest 60's the car has ever had. 4th pass almost made it but black tracked into a violent shake that knocked something loose in the dash and shut her down. Girl in the other lane had me covered by a solid tenth so wasn't going to matter much anyway.
     
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  10. Mike Canter

    Mike Canter Top Dragster

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    I am a little confused. There is no way an 81 pill can provide the correct AFR from 1400 ft to 4000 ft. That is absolutely impossible. On an average for every 100' change in air density the pill will change one size.
     
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  11. Bjs344

    Bjs344 Member

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    Lol. You hemi guys....

    I have more blower than fuel pump. Pretty sure I have more fuel pump than crankshaft, but trying real hard not to find out.

    Have to admit, I've stared long and hard at the 70s section of the pill box for a little while now but so far I've refrained.

    That's just ahen I'm trying to go fast though. I'll go as high as a 95 to slow it down for bracket racing.
     
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    Last edited: Aug 8, 2017
  12. greenracing

    greenracing Member

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    in other words - it's so fat that it can't hurt itself and even with air change it's still fat :)
     
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  13. Bjs344

    Bjs344 Member

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    No, actually I keep it pretty tight. Usually I go for 3/4 chalk if I'm trying to go fast on the 1/4. That only seems to translate to about 3/4 gray (no chalk) on the 1/8. I Might go after it on the 1/8 mile sometime if I know I can get a good bearing reading afterwards, but for now it was good enough to get into the 3s this past weekend.

    I was going to post a pic of my pulley cabinet so you guys believe me but I haven't got around to it.
     
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