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A3 vs S3 A power to weight thingy (cant think of a title thats best I can do lol)

Discussion in 'A3/S3 Forum (8L Chassis)' started by cjsuk, Jun 29, 2013.

  1. kwistof
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    kwistof South East Events Moderator Regional Rep

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    With it being built by Bill, I'm certain it was all bolted together properly and was a very tight car at those speeds.

    I've been similar speeds in extremely un-road worthy cars....but then that's what you do when you're a young teenage lad, have access to private land and get given cars to play in :)
    #41
  2. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    bear in mind, simple "power-to-weight" only goes so far.

    Once you start approaching/exceeding "motorway speeds" the air resistance means the more powerful, but heavier car will start to win out.

    think of it as "Spare-power"-to-weight...

    If you take a 1500kg S3 with 270hp, and a "matched" 1250kg A3 with 220hp, both having a power to weight ratio of 180hp/t

    at 100mph you might be using 100hp just to keep the car moving, so in a 220hp A3 you've only got 120hp left to actually accellerate with, whereas the 270hp S3 will have 170hp "left", giving a "spare-power"-to-weight figure of 96 for the A3 and 113 for the S3... meaning at that point the S3 would be accellerating faster than the A3.

    As the speed climbs the air resistance climbs rapidly, the amount left shrinks, and the more powerful car will begin to pull away.
    #42
  3. badger5
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    badger5 RIP S3dave Site Sponsor

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    resistance is a square of speed is it not, drag wise..
    100bhp more does'nt stretch as far as you would hope...

    1/4 miles tho.. meh.. not an issue
    #43
  4. rhubarb4
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    rhubarb4 Certified Jardo Slayer

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    I want to see what mine makes on the quarter mile now, hoping I have a decent start.
    #44
  5. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    aye, air resistance is related to the square of speed, so becomes big very quickly as speed increases.

    Like you say not really an issue for a quarter mile, but on a higher speed dash like motorway/autobahn runs it becomes more relevant.
    #45
  6. superkarl
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    superkarl MAN OF STEEL

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    i hit about 267 mph so im reet
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  7. Scullies
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    Scullies Active Member

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    I think you might have a boost leak, your car sounds a bit slow and those figures in your signature are way off. You could do a lot more!
    btw what clutch do you use to put that power down?
    :)
    #47
  8. Paradox1
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    Paradox1 Active Member

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    standard clutch:undwech:
    #48
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  9. superkarl
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    superkarl MAN OF STEEL

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    its carved from a piece of the earths core
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  10. 16Klappe
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    16Klappe Princess Slayer

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    But at this point the extra K03 torque kicks in.

    So in short, A3 ftw.
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  11. Paradox1
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    Paradox1 Active Member

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    as if there was any other possible outcome.....
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