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Rpm vs speed vs diff ratio

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    Rpm vs speed vs diff ratio

    I questioning myself . I have 325is with 3.73 lsd diff . (PO said it was 4.10 but when I turn the Input shaft , the output shaft turn close to 3.75turn ) What shoul be my rpm at 100kmh with the right tire size ? I took a pic today and some of my friend tell me that im reving high. In the pic I was in 5th gear.

    #2
    https://e30goodies.com/gearing-calculator/

    It should be 2750 rpm with 3.73 and 105 km/h.

    Comment


      #3
      Thanks for the link .
      but the Gear ration you entered are not the one that I find on the web and e30zone.

      + the diff ratio is 3.73 and not 3.71
      + tire are not 215-55-16.

      even if I enter everything right on this chart .
      my car is over rev .

      what can explain this ?

      rev’limiter look at the good place
      my speed do said the right speed ( verified side by side with digital Honda Civic lol ..)

      the only explanation is maybe my final gear in tranny was replace by another ??

      Comment


        #4
        What is your tire size? Also the E30 speedo is quite inaccurate, which can be fixed mind you... Without knowing your tire size, this is all an exercise is nothing.

        Comment


          #5
          Originally posted by Iloveboost View Post

          the only explanation is maybe my final gear in tranny was replace by another ??
          With a 4.1 differential and 195/65/14 tires, the calculator shows 3250 rpm at 108 km/h.

          That's close to your numbers.

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