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Thread: Interesting top speed challenge article with an S13

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    Guest fullmetalgasket's Avatar
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    Interesting top speed challenge article with an S13

    For reasons that I completely fail to grasp I'm on the mailing list for a site called Grassroots Motorsport in the states - Besides generally checking out the articles on the 24Hrs of Lemons for humour factor I just delete on receipt usually.
    Today though I had a link to the following article turn up and though it too good not to share:

    https://grassrootsmotorsports.com/articles/absolute-velocity/


    Enjoy

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    Guest Sean-B's Avatar
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    Cool!

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    Guest ANDY black s13's Avatar
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    Good find that man, that must be the fastest a set of ebay fake kouki tailights have ever gone

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    But the RS13 has already taken lots of speed records.

    MotoIQ reduced a SR20 to SR15VET. 165mph at El Mirage.
    http://www.motoiq.com/MagazineArticl...El-Mirage.aspx
    Bonneville 178.9mph
    http://www.turbosmartusa.com/news/mo...lle-salt-flats

    This one has held about 7 records. E/FALT record of 235.890mph in 2006 and some lurid stories of high speed wheel spinning slides.
    http://www.speedhunters.com/2009/08/...s_fastest_s13/
    Dunno if it got sold.
    The Buick straight 8 didn't do any good. So that's just 3 engines for 7 records.
    http://www.landracing.com/forum/inde...c=13587.0;wap2

    Racing on salt/dust is totally different to tarmac. The coefficient of traction is 0.5 at best and can be as low as 0.3. Salt surface is kinda loose but as wheelspin is easy you can leave black stripes. Tyre rolling drag is higher.

    Some physics.
    Traction force = coefficient of traction x reaction on driven wheels.
    F =M u x B x Mass x g
    Mu = coefficient of traction
    B = fraction of mass on driven wheels (1 for 4wd)

    Drag force = 1/2 air density x CdA x speedē + Cr x Mass x g.
    Cr = Coefficient of Rolling resistance
    CdA = drag coefficient x frontal area

    As you stop increasing speed and just spin the wheels (200mph+ wheelspin on salt!) when drag force exceeds traction force. Equating the 2 and solving for speed.

    Speed = root ((Mu x B - Cr) x Mass x g / (1/2 air density x CdA))

    You can't change Mu that depends on condition of the salt and changes every day, air density is what it is and you have little control over Cr. On dirt the Coefficient of Rolling resistance can be 10 times higher than on tarmac.
    You can reduce CdA a bit - 5-10%.
    Aero generated down force is useless as it increases CdA and eats power that could be used to push the car faster. Suction from underbody "ground effect" can be "free".
    So it's mass and mass fraction on driven wheels that are the key to going quick on salt.

    So you put junk in the trunk. Has to be bolted/welded in. And then you hang more off the nose or move the front axle forwards to stop that lifting.

    Then when you have your degree in Mech Eng you can go build the fastest Datsun ever. A Sunny 120Y. 1985 Tom entered the 200 MPH Club with a AA/BFCC record of 294.863 mph

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    That's all very well Peter but what was his 60ft time ?

    Sent from my XT1032 using Tapatalk

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    Quote Originally Posted by Jonny Wilkinson View Post
    That's all very well Peter but what was his 60ft time ?
    Doesn't matter it gets a shove from a Dodge Ram.

    Drag racers need a new crank every 4th 1/4 mile run, they won't make it to the first timing lights at 3 miles.

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    Guest ANDY black s13's Avatar
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    but how much of the 120y is left aside from the rear lamps? as it looks a bit modified from what I remember,
    if it was a stock body doing near on 300mph that would be impressive

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    Sorry, it was a reference to a certain banned gentleman from years ago who would bring every thread around to 60ft times. Nakimoto ? My memory's gone

    Sent from my XT1032 using Tapatalk

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    Quote Originally Posted by ANDY black s13 View Post
    but how much of the 120y is left aside from the rear lamps? as it looks a bit modified from what I remember,
    if it was a stock body doing near on 300mph that would be impressive
    It was based on the 120Y coupe, a fastback. May have had the roof lowered but front door pillar back is about stock, the rear side window lower edge to body is still there, the triangular rear quarter window has been filled in. Obviously the rear end has been tubbed to allow lowering and take tyres with 28" dia and a quick change rear axle would have been fitted.


    They also made a Tigra over 20 years before Opel.
    Last edited by skyshack; 09-10-2016 at 10:32. Reason: change url to img tags

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    Guest ANDY black s13's Avatar
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    yea close enough nigh on near identical , a bit like triggers broom,,,yes it's the original broom from when I started,,, its had 4 heads and five handles
    but shouldn't mock the massive achievement

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    Guest fullmetalgasket's Avatar
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    Quote Originally Posted by Jonny Wilkinson View Post
    Sorry, it was a reference to a certain banned gentleman from years ago who would bring every thread around to 60ft times. Nakimoto ? My memory's gone

    Sent from my XT1032 using Tapatalk
    Nah, Nakimoto was argumentative and sometimes abusive iirc, then you had Mr. Akimoto with his world's fastest 200sx and gay manservant who finally pushed it too far.
    You're thinking of Bodleytunes I think
    On that subject I wonder what the world record is for top speed in a Renault 21?

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    Quite right. Bodleytunes haha

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