boost on two step

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by ansleev, Sep 2, 2009.

  1. ansleev

    ansleev Member

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    i have a screw leave around 5000 rpm on two step it builds 40 pounds of boost is that in the range that most of you guys have on two step
    thanks
     
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  2. GregM784

    GregM784 Member

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    The roots promod i work on has 22psi on the two-step. that is a 14 on a 521 BAE, at 5500RPM
     
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  3. GregM784

    GregM784 Member

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    of course, we are not making 40 at any point in the run, let alone on the limiter
     
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  4. JRB

    JRB Guest

    Ive got a couple different combos I can share with you. All customer cars. All Pro Mods as well:

    *Roots blown 450 c.i BAE 5 @ 29 over
    34 lbs @ 5300
    *Screw blown 481X (C Rotor @ 100 over)
    37 lbs @ 4400
    *Screw blown MBR Hemi (D Rotor @ 92 over)
    40 lbs @ 5800

    Greg, is that car you say you help on Baileys car? Cause his numbers are pretty close to that.
     
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  5. GregM784

    GregM784 Member

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    Yes Sir it is.
     
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  6. wheelie

    wheelie Member

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    36lbs, PSI Screw @ 4000 RPM, 92% OD
     
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  7. JRB

    JRB Guest

    Dan,

    Congrats on the recent success you have had since the "switch" to the dark side. Don't know if its a permanent thing for you or not, but your doing good!
     
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  8. GregM784

    GregM784 Member

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    I look forward to working on Bailey's car more, and learning more. Lot's of electronics & gadgets, not used to them in the Nostalgia arena. Cya at the Gov Cup Jason
     
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  9. ansleev

    ansleev Member

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    how much timing are you pulling out at hit if any on clutch cars i know weight tire gear ratio etc all play in just in general
    thanks
     
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  10. wheelie

    wheelie Member

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    Thanks! Working on a turbo car right now though, may run both next year :D
     
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  11. RACEFACE

    RACEFACE Member

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    Boost at stage

    So you guys are saying that you are building all this boost because its on the two step controler at stage? Or are you making that much boost at apx 5000 rpms no load ?
     
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  12. JP

    JP Member

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    AS soon as your engine gets to its rpm limiter ie 5000 rpm on the two step it will be within 5-7 pounds of the max boost you will make on the run..

    Its not to be confused with no load rpm . No load rpm its only 5000 with the butterfies closed, on the two step the butterflies are completely open.
     
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  13. mudmankipp

    mudmankipp New Member

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    ok...im new to the clutch set up on a blown dragster. you put the motor on a two step with the clutch mashed to the floor,then drop the brake and side step the clutch. as posted above, that would be free spinning the motor till the clutch hits. is the throtle on air cyl or just a two step. ps this is my daughters car and we are both learning :D
     
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  14. Mike Canter

    Mike Canter Top Dragster

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    If you have an air controlled throttle combined with a Two Step you will not make the boost because the blades are NOT open. You have to have the blades wide open to make all that starting line boost. If you use a Two Step without an air controlled throttle you will make tons of boost at stage. Some racers use the combination of air controlled throttle and Two Step to keep the boost down and be accurate on the launch RPM and not have to worry so much on swapping feet or controlling the fuel since the blades and Barrel Valve are not wide open. If you use just a Two Step without the air controlled throttle then your blades are wide open as it the barrel valve so lots of fuel going into the motor so fuel control is required.
     
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  15. mudmankipp

    mudmankipp New Member

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    thanks mike, looks like a fuel managment system might be in my future. this car has been a learning curve for both of us and we are loving every pass we make. any suggestions on a fuel managment system.
     
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  16. wildman

    wildman Member

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    Really?

    Ok.... I must be living in the dark ages. I was always under the impression that a 2 step on a blown car is major no-no. Are we talking the standard msd 2 step module or a digial 6 type ignition? This would be a wonderful change for me as the air bottle / air cylinder has been a PITA lately.
     
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  17. GregM784

    GregM784 Member

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    THey are leaving on a two step, like a super class car. When our car goes on the two step, we dump a bunch of fuel (elec solenoid that is engaged while on the 2 step). It sounds horrible, and i can't believe it works, but it does. Most of the time.

    I prefer the air launch deal. I understand it takes slower to get the boost to come up, but when you are pulling 20* of timing out at the hit anyways, wtf?

    Just my opinion
     
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  18. mudmankipp

    mudmankipp New Member

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    here we go again. pulling timing ? we have been running 28* locked down. we run a 44 on a 526 with a 1471 with 42 over. do we need to a 6 shooter for this combo
     
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  19. Mike Canter

    Mike Canter Top Dragster

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    You only need to pull timing if you can't get off the line but in moderation. You can pull timing with a Six Shooter and some kind of timer or with a 8973.

    Greg you are pulling 20* out on launch????? Yea, WTF. The problem in pulling out that much is that you can have a problem with traction because you may not be hitting the tires hard enough to plant them. Also coming off of too much launch retard can cause you to spin the tires because you didn't plant them and then apply full power. That can be a bad downwards spiral.

    What I think is amazing is to watch a TAFC launch at 7000+ rpm with no launch retard and get traction and .95 sixty foots. That is because they are firmly planting those tires.
     
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  20. JP

    JP Member

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    Hi greg

    Mi combo is a 1471 retro high helix at 30%, brad5 525 with a .750 pump.

    We stoped taking fuel while in the two step and that allowed us to not take timming away at the hit.

    In other words the engine became more calmed at the hit so we where pulling 8 degrees, now we dont , we usually take 3-4 when the track is bad .

    hope this can help
     
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