What trap speed mean in the 1/4 mile?

Discussion in 'OT Driven' started by Kroze, Dec 14, 2009.

  1. Kroze

    Kroze Active Member

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    What?
    What does it mean when both cars trap at 107 mph but one run 12.6 and yet the other run 13.5???

    This confused me. Both cars should be equally fast on the highway right since they trap the same speed?
     
  2. GammaRadiation

    GammaRadiation Active Member

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    Trap speed is simply the speed at which you cross the line at.

    In your example the car that ran the 13.5 may have had a bad launch, bad shift, is far less aerodynamic, or may have broken traction at some point
     
  3. z284pwr

    z284pwr OT Supporter

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    One car has a better launch/60ft time so it makes it down the track faster. The other doesn't have as good launch/60ft time but has better top end speed. Example from the last drag race I went to. Pro Mod cars, 1 Turbo car was running same E.Ts ~5.98-6.08 but was running 10-15MPH faster at the end of the track. Not as good of launch/as much power as the Nitrous/Supercharged cars off the line but once it hit half track or so turbos kick in all the way it takes off like a rocket.

    They won't necessarily be equally fast on the highway, gearing can be a huge factor, one may be purposely built for drag racing so it hits it peak at 107 MPH but the other may be built for highway cruising so it hits 107 and was plenty more left in it and with a highway not being 1/4 mile long it can go for as long as the idiots decide they want to endanger everyone's life doing 107+ on a highway

    Trap speed is actually the average speed of the last 66ft of the track
     
  4. deusexaethera

    deusexaethera OT Supporter

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    Assuming drivers of equal competence and cars with similar drag coefficients:

    A car with a shorter elapsed time but a lower trap speed has really good acceleration off the line but crappy acceleration once it's up to speed, but since it got a good launch it was still able to run the length of the track quickly even if it couldn't speed up much after it got out of the low gears. So basically it has wide-ratio gears, i.e. really short low gears and really long high gears.

    A car with a longer elapsed time but a higher trap speed has crappy acceleration off the line but better acceleration (relative to the first car) once it's up to speed, so while it took a while for it to get up to speed, in the last few yards of the run it was able to accelerate faster than the first car. It probably has close-ratio gears designed primarily for highway driving and/or a crappy turbocharging system that takes forever to spool up so it can't get going fast off the line. A good example of this would be my passat, which I swear accelerates faster from 60-80 than it does from 0-40, because it has a tiny engine with a tiny turbo and it weighs 3500lbs, but once the engine is up to speed and the turbo has lots of exhaust pressure to run on, it does its job quite well.
     
    Last edited: Dec 14, 2009
  5. GammaRadiation

    GammaRadiation Active Member

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    After you take out 6000 other factors.
     
  6. Smelly-Kitten

    Smelly-Kitten Dept. of Redundancy Department *Side Pipes

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    Less aerodynamic (than another car of same ET and higher trap) would mean a lower trap, as it can accelerate quickly in the first part of the track lowering ET but is having trouble pushing wind in the latter part lowering trap speed.

    In the OP's example, if both cars got to 107mph in the same distance - the one with the lower ET could have an unussually low trap )in comparison to cars normally at his ET) due to aerodynamics all else the same.
     
  7. dr.zed

    dr.zed DR.ZED OT Supporter

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    :) Close.

    Its the AVERAGE of the last 60 ft. Not exactly what you're traveling at.

    Watch drag racers deep stage for quicker ETs and less MPH at the back end and visa versa.

    Generally trap speed is what tells you "really" how fast the car is when it gets moving. Launches are what is going to impact the ET the most.

    So a shitty launch on shitty tires could yield a 13.5 when the car really is a 12.5 car. However the MPH tells a better story all things not being equal.

    The ZR1 is a 10.74 @ 133 MPH car. 133 MPH! Hot dayum that is fast!

    Stockish LSx f-bodies trap in the 105 -108 mph, really decent! However, an SRT4 with shitty FWD launches may end up only doing 13.5 but hussles at the end at 105 MPH. Thats the highway race equalizer number there.

    :)
     

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