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Best diff ratio for turbo cars

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  • #16
    I have a Tremec TKO dogbox that I run with the 4.10 diff on my S14 turbo. Speed in gears are:

    45
    68
    100
    128
    156

    THis is almost equal to running the Euro CR box with a 3.25 diff, but 3rd and 4th are much nicer on the TKO. I find it ideal on the street. On the track, you'd surely want a taller 1st gear.
    Anders

    "Objects in mirror are losing..."

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    • #17
      The 'ideal' diff ratio really depends upon factors such as vehicle mass, traction, transmission gearing, engine displacement and off-boost torque, and turbo size.

      Smaller displacement engines, larger turbos, greater mass, and better traction tend to favor higher numerical diff ratios.

      Larger displacement engines, smaller turbos, less mass, and limited traction are better off with lower numerical diff ratios.

      In any case, it's definitely worthwhile to work out the speeds and shiftpoints vs. gearing before making a decision.
      2003 Mitsu EVO VIII - 2.0L / 600+whp
      1988 BMW M3 turbo - Work in progress. . .
      1986 SVO Mustang - Work in progress. . .

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      • #18
        Factory gears are way too short to really take advantage of time in boost. A lower numbered gear like a 3.46 or a 3.25 would help spool time and allow for more time in boost in each gear.
        Need a good mechanic/fabricator/performance shop in SoCal?
        http://www.r3vlimited.com/board/showthread.php?t=155404

        Castro Motorsport

        12600 Sherman Way, Unit C
        North Hollywood, CA 91605
        (818) 765-3606

        The Purple ///Monster Build:
        http://www.s14.net/forums/showthread.php?t=47251

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        • #19
          Agreed, I like the 3.46 ratio for a US spec 265 trans. I think the road manners would be similar to a 4.10 under boost, with higher shift points.
          Rich!

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          • #20
            Originally posted by ///schwartzman View Post
            Agreed, I like the 3.46 ratio for a US spec 265 trans. I think the road manners would be similar to a 4.10 under boost, with higher shift points.
            Yea, Castro's m3 with the 3.46 is awesome in NA form, with only about 190whp! would love to see how crazy your will feel with 2x the power! :blues:
            Need a good mechanic/fabricator/performance shop in SoCal?
            http://www.r3vlimited.com/board/showthread.php?t=155404

            Castro Motorsport

            12600 Sherman Way, Unit C
            North Hollywood, CA 91605
            (818) 765-3606

            The Purple ///Monster Build:
            http://www.s14.net/forums/showthread.php?t=47251

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            • #21
              Just left Chris' seeing the car makes me miss driving it. I got your tappet gonna see if Rick Kemph has one to match.
              Rich!

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