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Thread: 3.91 in A6 auto scale correct?

  1. #21
    I found auto scale can be wrong or I'm missing something.
    Why in stock file current gear ratio is different than calculated?
    let's say 2004 corvette, I belive there is 3.42 installed, stock values:

    Mile 31*027
    rev-trans 12.6836
    ratio 3.42
    trans rev 2446

    calculator says
    current: 26 and 3.42
    calculated 26 and 3.15

    When I enter new as current, so 26 and 3.42, then he rescales speed and
    rev-trans 11.6953
    trans rev 2652

    When I enter new as calculated so 26 and 3.15 then nothing is changed in tune except ratio that is changed to 3.15.

    If I type similar data in Bluecat software, I get speeds close to 3.15 and they are similar to this from factory tune.

    Could be that in tune factory speeds are not adjusted? Or they don't need to be adjusted because if only ratio is changed he calculates it self?
    Eastern and Central Europe American Muscle and Harley-Davidson tuning
    www.hd-customs.pl
    http://www.facebook.com/hdcustomspl

  2. #22
    Senior Tuner Russ K's Avatar
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    Dec 2005
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    Regina, Sask.
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    4,200
    Looks like your working on an A4. The calculated 3.15 is correct, as the A4 either had a 2.73 or a 3.15 gear ratio. I don't know why GM set it up that way.

    Russ Kemp

  3. #23
    Thanks for answer.
    I didn't want to create separate thread for this, so asked here.

    Then looks gear ratio field is informational only and not used by PCM.
    Eastern and Central Europe American Muscle and Harley-Davidson tuning
    www.hd-customs.pl
    http://www.facebook.com/hdcustomspl

  4. #24
    Quote Originally Posted by Russ K View Post
    The auto scale is correct. 3.45/3.91=.8849x113=99.99

    Russ Kemp
    Russ,
    Im just curious for a learning moment, what's the number 113 used for in your equation?

  5. #25
    Senior Tuner Russ K's Avatar
    Join Date
    Dec 2005
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    Regina, Sask.
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    Quote Originally Posted by Phil'sC5Vette View Post
    Russ,
    Im just curious for a learning moment, what's the number 113 used for in your equation?
    113 was the OP's 4-5 shift MPH with the 3.45 gears.

    Russ Kemp

  6. #26
    Tuner
    Join Date
    Sep 2008
    Location
    Aurora, IL
    Posts
    156
    Maggie TVS1900 going on this spring. Gonna see how long I can handle the 3.91's with the boost, but I've had some suspension work since I last checked in.

    BMR Super Pro cradle kit
    BMR trailing arms
    BMR adjustable toe rods
    BC coilovers
    New 285/35/19's out back for the street and same Hoosiers for the track

    Everyone is telling me I'm crazy but I yet to find anyone chime in with their experience with tuning this setup.

    I'm going to a whole new shop this spring to have the tune completely started over from scratch and will update this thread then.

    2009 G8 GT - White Hot

    226/234 601/601 112+4, Yank SS 3600, SLP Longtubes, Magnaflow exhaust, Rotofab, 3.91 Rear

  7. #27
    Potential Tuner
    Join Date
    Feb 2019
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    6
    Help! Top speed...shift denied 5th -> 6th!

    I installed GM 3.91 gears kit on my 2010 Camaro L99 A6 (6L80) and I recalibrated my tune with hp tuners with the gire/tyre wizard.
    Stock tyre 27,79 (no change)
    gear ratio 3.27 -> 3.91
    --------------------------
    multiplier = 0,836

    I try top speed (German autobahn) but I cannot shift 5th->6th (DIC shift denied) and the car comes to rev limiter 5900 rpm (approximately 228 km/h = 141 mph).

    which tables should i pay attention to?

    attached my tune.
    Attached Files Attached Files