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1/4 mile time calculation

Discussion in 'VT - VX Holden Commodore (1997 - 2002)' started by kangavxss, May 28, 2014.

  1. kangavxss

    kangavxss New Member

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    Does anyone have a formula for working out 1/4 mile times for a modded vxss ( cam, otr, full exhaust, 3.73 diff gears, mafless etc typical mods). I dont live or have access to a drag strip so always wanted to know roughly what my ss would do. I did find an online calculator (Xcceleration) that asked for rwhp (355rwhp - 265rwkw) and weight of car (approx 3300lbs i think) and it gave a time of 12.2 seconds. The calculator doesnt ask if its manual (its an auto) or diff gear ratio ( 3.73) if that has effect on the time. Is the 12.2 about right? I know there are many variables but a ballpark figure is what im after. Also whats the 1/4 for a stock ss. Like to know my mods have paid off...lol.. Thanks for ur help...
     
  2. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Still not going to have the same weight as an actual time slip though will it. Can see the conversation now...

    "Hey man, took my car to the strip and it did 12.5, here's my time slip. How fast is your car?"
    "According to the online calculator it does 12.2"
    "....."
     
  3. AirStrike

    AirStrike Administrator

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  4. Pollushon

    Pollushon Boost gives me a bar....

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    Desktop dyno and drag purport to do this accurately....it's a load of shit IMO.
     
  5. gm1961

    gm1961 New Member

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    Hi All

    just google / search for online speed calculator
    but here is a good site with plenty of links
    also you can find excell sheets

    The best program to use is 1/4jr & dyno these are older dos programs, for windows you can use dyno 2000
    they may turn up on a google search or a torrent, but they are commercial ( bought / paid ) programs , i am just pointing you in the right direction not telling you to do something illegal, there may be limited or trial versions available.

    For free online simulators / calculators i use this site with a fair few web pages listed

    Wallace Racing - Automotive Calculators

    you may also need a metric to imperial calculator, use a online one, but there are some good utilities you can download

    But the results are not perfect, instructions are vague, so some may be for rear wheel HP, but dont actually say , others ( usually USA ) like to use engine flywheel HP as a example

    So some stats for a VT SS

    We know the weight is 1643kg ( hmm my rego papers say my VT SS 304 is 1504 )
    so 1643kg = 3662 pounds

    We know it is rated 179kw , this is 243 HP ( roughly we use 1/3 to go HP to KW , also as a coincidence we also use 1/3 to go from engine KW to rear wheel HP as driveline loss is about 1/3 , so sort of funny a 180kw engine , should show 180 hp rear wheel dyno as a guide )

    the maths in some 1/4 programs came back as follows - best time 14.33 , which is think is a bit high , i dont have any proper trustworthy articles here but i would be suprised that the Gen3 would be a 14.3 car , the 304 to me would be a 15.5 -16.0 car

    Power to Weight Ratio: 14.91
    60 Foot E.T. : 1.99
    1/8 Mile E.T. : 9.04
    1/8 Mile Trap Speed : 75.15
    1/4 Mile E.T. : 14.33
    1/4 Mile Trap Speed : 93
    1/4 Mile Trap RPM : 3,985


    regards
    george
     
  6. kangavxss

    kangavxss New Member

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    Yeah i know i could go to Adelaide International but weekends see me working most of the time so im out of luck there for the time being..
     
  7. kangavxss

    kangavxss New Member

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    thanks gm1961. very informative.
     
  8. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    I just did the calculation for the VC at Kwinana Motorplex.

    Your 1/4 Mile ET is 11.81
    Your 1/4 Mile MPH is 117.27

    Bit like a happy dyno.....
     
  9. immortality

    immortality Donating Member

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    Just like the Moroso calculator, these results are a best case scenario. No road car is going to have perfect traction or gearing etc.

    Using those kind of calculators look at the MPH as this won't change much as it takes X amount of power to achieve Y speed. Elapsed time is going to be slower.
     
  10. st3r3otyp3

    st3r3otyp3 Donating Member

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    anywhere from 12.5-12.9 Id say don`t get overhyped you may get deflated, where does it make max torque with no converter this is important.
     
  11. kangavxss

    kangavxss New Member

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    Nah not expecting massive gains over when it was stock ( feels a hell of a lot quicker). heres the dyno but shows only tactile effort not torque. Red curves after cam install. Green was mafless and exhaust only before. All pre diff gears change. Cheers
    [​IMG]
     
  12. st3r3otyp3

    st3r3otyp3 Donating Member

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    Oh well, you can work out the torque figure using math but you will never know the peak, I`d say it would be lower in the RPM been a small stick, prolly around 2.5- 3k.
     
  13. gm1961

    gm1961 New Member

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    Hi All

    Depends what you are chasing, the maths stats are a guide or the best expected outcome for a given set of info / input

    Sure on the day, runs can vary easily by 2 seconds depending on air temp / heat , tyre pressure, stickyness of the track, engine temperature and most importantly driver reaction time.

    A mate of mine has 2 'weekender racers' one does best of 11.2 and the other more of a streeter of 13.0
    but the wrong person in the 11.2 car can get it down to 14's

    Torque Vs HP , thats a always argue event, but day to day street it torque, there is no real need to rev a engine to high RPM to achieve output, all you do is strain and wear components

    Say you take a typical engine does not matter which one 5.0 holden or or 5.7 chev
    Now i am not comparing holdev Vs chev , but the same style of engine eg 304 highHP revver Vs 304 torque ( or Gen3 Hi RPM revver Vs Gen 3 torque )

    At the drag strip its almost irrelevant, at 1/4 mile or 400 meters, unless you run something like 2.60 gears yuor car will achieve maz RPM and exit speed by 300 meters, very few cars are slow reving or geared to keep acceleration at the 400 meter point, actually some cars you can even back of before the line or switch of the engine the speed you have reached will keep pushing you

    Its like doing 80kph and taking your foot of the accelerator the car will still go 80-80-80-79-79-79-78 etc it wont back off fast like say when you are in first gear and take your foot of the accelerator and the car revs down and slows down , this is the combination of say your first gear ration * your final drive , for example 1st = 3.5 * diff of even a 3.08 = 10.78 , this is why the revs drop of much faster


    Back to torque vs HP , 2 identical motors, one is say 400HP at 7000 the other is 400HP at 5000 , which one will last the longest , the one that lives at lower revs, in a perfect world it has less revs so less wear and tear , plus the engine has less chance of becoming a grenade at lower revs.


    The dyno and dyno 2000 are great programs, i loved spending time on them going through cam catalogs and running simulations, beats buying say 4 or 5 cams and outing them together to see what happens.

    regards
    george
     
  14. Munz

    Munz Right Foot Action

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    12.8 @ 110mph would be my guess
     
  15. Towcar

    Towcar Member

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    reminds me of the Canada on strike episode of South Park.

    The boys make butters do a you tube video to make money, they go to the government for their internet money to find it is theoretical money and not worth anything!
     
  16. ari666

    ari666 250,000 hits

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  17. kangavxss

    kangavxss New Member

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    mmm might have to try and find a long private road and do some runs with Torque or Dash Command OBD 2 software i have on my Android and test her out (Im pretty sure one of those have
    the ability to do record and graph timed runs). Cheers fellas.
     
  18. ari666

    ari666 250,000 hits

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  19. kangavxss

    kangavxss New Member

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    I know but cant get there on dates they run em unless i take a sicky...damn...
     
  20. AirStrike

    AirStrike Administrator

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    Annual leave.
    Using some app on the street is pointless to compare with an actual quarter mile time. Might as well pull a number out of a hat.
     

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