Clutch car 2 step

Discussion in 'PSI Superchargers Tech Questions' started by Blown Altered, Dec 3, 2012.

  1. Blown Altered

    Blown Altered New Member

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    Is there a performance advantage to using a 2 step rev limiter while staging a blown clutch car or are they used mainly for consistancy for driver who can't stage at the same rpm or swap feet properly. It seems that the motor would be up on boost with butterflies wide open but possibly rich on fuel system with barrel valve in wide open position and no load on motor with ignition cutting out every other cylinder?
     
    #1
    Blown Altered, Dec 3, 2012
  2. Mike Canter

    Mike Canter Top Dragster
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    Heck yes there is an advantage of launching with 20+ lbs of boost. You limit the fuel with a fuel bypass solenoid when up on the Two Step. The consistency also helps.
     
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    Mike Canter, Dec 3, 2012
  3. turbo69camaro

    turbo69camaro Member

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    I looked at an old run i had 526ci brad 5 20% nitro staging the car @ 5500 0 boost.... .08 20 lbs and .2 30 lbs also pulled 0 timing out.960 60 ft and this was in 2007 looks like its easier on parts than a wot 2 step. Also this was with a littlefield 14-71 far from a max tricked out blower. Not sure if you 2 stepped and had to pull timing out at the hit if it would be fast or not
     
    #3
    turbo69camaro, Dec 4, 2012
  4. Mike Canter

    Mike Canter Top Dragster
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    Think about what you just said. If it didn't help then why is it every blown ADRL or NHRA promod using a 2 Step. There is no way you could be competitive without a 2 Step. As long as you keep the fuel flow in the correct area while on the 2 step you will not damage any parts. We made 190 runs this year up and through the Snowbirds and never damaged a part because of the 2 Step and we make a bunch of horsepower. With a Roots blower at 14.5% OD we have run the 1/8 mile in 3.88 seconds at legal NHRA PM weight.
     
    #4
    Mike Canter, Dec 4, 2012
  5. TOL

    TOL Active Member

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    Hey Mike, is there any advantage to having a 2-step AND an air throttle both working together? I recall seeing some ADRL cars run this but I never really understood why?....
     
    #5
    TOL, Dec 4, 2012
  6. Mike Canter

    Mike Canter Top Dragster
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    Some racers think that it is required to keep the BV from being wide open so they have less fuel flowing. It also limits the amount of boost. I have never seen a front runner do it.
     
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    Last edited: Dec 4, 2012
    Mike Canter, Dec 4, 2012
  7. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    front runner

    in the interest of fair reporting the last two PX Champions (Mick Snyder and Jason Hamstra) leave at part throttle, not WOT. The majority of the class leaves WOT, but it's not entirely accurate to say no front runners don't use WOT.

    with the much higher overdrive the screw blowers run, it's a bit harder on belts. a roots has much lower overdrive so I don't think it's as much drama on the belt.

    when Bartone was running the 2-step in TAFC before they outlawed it, Boggs told me they were lucky to get 2 runs out of a belt.
     
    #7
    Will Hanna, Dec 4, 2012
  8. underby6

    underby6 Active Member

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    I leave at partial throttle w/ a 2 step governing it. Leaving at WOT on a screw setup is the wrong way to go. The cars I've worked with who have done it maybe get 2 runs out of a belt, kill intake springs, and generally aren't controllable on a consistent basis.

    Brandon Booher
    NHRA TAD #34
     
    #8
    underby6, Dec 4, 2012
  9. Mike Canter

    Mike Canter Top Dragster
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    I am talking about Roots blowers on ADRL and NHRA legal PMs not a screw blower car and the original question was about a clutch car and not a converter car. My statement still stands. A PX car is a little radical and one TA/FC that tried it for two races does not set a trend. I know lots of other screw blown promods that Two Step WOT. There does seem to be a problem with quill shafts on screw blowers using a 2 Step
     
    #9
    Last edited: Dec 4, 2012
    Mike Canter, Dec 4, 2012
  10. TOL

    TOL Active Member

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    Would this help to solve the problem?......

    http://www.dmpeinc.com/superchargers/index.php/other-components/psi-screw-drive-absorber.html
     
    #10
    TOL, Dec 5, 2012
  11. turbo69camaro

    turbo69camaro Member

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    I just made a comment that...........doing it the old school way which is hard for for some to do i still had 20 psi @ .08 and 30 .2.this was roots at 40% O.D I understand it is easier to mash the gas and go. When you 2 step do you pull timing out at the first part of the run ?
     
    #11
    turbo69camaro, Dec 5, 2012
  12. Mike Canter

    Mike Canter Top Dragster
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    Pulling timing out depends on how much power you have and how well your 4-link is and how good your car is. That is hard to say just out of the blue. Some launch with zero retard to plant the tires then pull out timing. The big trick is to monitor your driveshaft speed and see what is happening.
     
    #12
    Mike Canter, Dec 5, 2012
  13. JustinatAce

    JustinatAce Member

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    You use 2-steps for the same reason every other door car and other types of clutch cars do.. So the launch/foot swap is consistent and the driver can focus on hitting the tree. It isn't power. Turbos can leave with 40+ boost at the step and you almost can't get enough power out of them. Those big balloons of rubber on the back of your car are only going to take so much no matter what's turning them. The foot swap and launch RPM is imperative in every car, but 4-link cars especially since all your suspension preloads are setup for a certain amount of torque transfer. If you're a typically a .070 light driver swapping, it might take you down to the .040's or .030's because you're focused on the tree and the car should be more consistent. So more consistent launch and you probably pick up .03 on the tree in eliminations.
     
    #13
    JustinatAce, Dec 5, 2012
  14. overkill69

    overkill69 Member

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    2 step

    Kinda hijacking the thread from clutch cars but with a converter we launched wide open two step and airthrottle with a roots and screw. Neither showed a substantial gain basically leaving from low boost to huge boost at around 4000rpm. With the screw we fought dropped cylinders even with massive fuel leanouts on the 2 step with the air throttle. Eventually we gave up and launched wide open and killed 2 quill shafts but kept the cylinders lit.
    We were running a chevy combo. If we get a hemi we'll go back to the 2 step with air throttle.
     
    #14
    overkill69, Dec 5, 2012
  15. turbo69camaro

    turbo69camaro Member

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    lol and doing it old school you get to surprise the guy in the other lane.I was at Tulsa and Scott Palmer was driving a friends screw blown clutch car lit the top bulb reved the motor up to 6000 and bumped in kinda freaked out Larry Jeffers in the other lane he had never ran a car that did that
     
    #15
    turbo69camaro, Dec 5, 2012
  16. Mike Canter

    Mike Canter Top Dragster
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    Justin, you are correct about the consistancy of a two step.You are actually correct in saying that there is no more power but that max power comes in a lot faster launching from a two step. There is a lot of difference in staging at part throttle with 5 lbs of boost and staging at 25 lbs of boost at wide open throttle. On a Roots blown PM the sixty foots and 330s really drop with a two step because of that instantaneous power when the clutch is released. The other advantage is I can adjust the clutch switch to control the clutch engagement point and control engine flare which is very important. Launching with 25 lbs of boost plants those tires and loads that chassis right now. It does take some chassis tuning to be able to take that instantanous power.
     
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    Last edited: Dec 5, 2012
    Mike Canter, Dec 5, 2012
  17. Vhodoo Racing

    Vhodoo Racing New Member

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    Most of the Aussie Door Slammers (Blown Pro Mod Style) are still doing it this way - very few on a 2 step and they almost have to run a sub 6 second 1/4 mile to make the feild now a days...
    Pete
     
    #17
    Vhodoo Racing, Dec 5, 2012

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