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  1. #26
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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Where did you find this calculator?
    Again...

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    So Corvette has the same speed for 3rd gear, 130ish depending on tires.

    Your car has wider power curve than stock N54, so the gearing should be longer than stock to take the full benefit of it. Also saving one shift is great.

    The calculator dows not seem to calculate the optimal shift points to max the area under curve across gears. What is needed is the whole dyno and the power at each rpm.
    From the calculator you can see that the most critical shift to second gear happens at 50 Mph and you land at 4000 RPM. Look at your power at 4k. It is not that bad at all. The torque at the wheels is huge there and you would still struggle with traction with street tires at the shift.

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    2 out of 2 members liked this post. Reputation: Yes | No
    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    Got the results based on this calculator:

    http://www.apexgarage.com/tech/gear_ratios.shtml
    you mean this one?

  4. #29
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    This ratio change would effectively make your car a 5-speed. The 6th gear will be useless for every purpose.
    There are two theories to arguing with women. Neither one works

  5. #30
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    Click here to enlarge Originally Posted by bmw335iguy Click here to enlarge
    you mean this one?
    That's it, I missed it I guess. Thanks!

  6. #31
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    Click here to enlarge Originally Posted by 654 Click here to enlarge
    So Corvette has the same speed for 3rd gear, 130ish depending on tires.

    Your car has wider power curve than stock N54, so the gearing should be longer than stock to take the full benefit of it. Also saving one shift is great.

    The calculator dows not seem to calculate the optimal shift points to max the area under curve across gears. What is needed is the whole dyno and the power at each rpm.
    From the calculator you can see that the most critical shift to second gear happens at 50 Mph and you land at 4000 RPM. Look at your power at 4k. It is not that bad at all. The torque at the wheels is huge there and you would still struggle with traction with street tires at the shift.
    Got a great calculator for determining perfect shift points based on dyno data, gearing and tires, just need to take time to move data over from dyno to the spreadsheet...does anyone know pf an easy way to export a dyno run from a Dynojet .drf file to a csv so i get rpm and torque in two columns? Winpep software doesn't look like it has that option..
    Click here to enlarge

  7. #32
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    The dyno plot will change for each gear so calculating shift points will not be completely accurate, but close enough. Average hp will decrease due to the rpm spread, but time shifting reduced. 6th gear would be better for cruising, increased gas mileage. The prob I see is potentially bouncing the rev limiter at the end of the quarter... i've never done it, but don't peeps hit the rev limit before the ceiling sometimes.

    I like the idea!

  8. #33
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    With Cobb redline is raised to 7200rpm actually and at this point I've gone almost all the way there on high boost a couple times without any issues...having said that, the power band of the car at that time wasn't flat to 7200rpm, it'd actually start to slightly come down around 6.4-6.5k rpm which made that point in the RPMs my best shift point for best times for a 3-4 shift...2-3 shift on the stock 3.08 final drive I usually do at near redline when racing

    i wish my Wavetrac carrier was reusable with a 2.56 ring/pinion final drive but i just found out that it wouldn't be...wavetrac has a separate unit for that so to do it I'd have to sell my current final drive and go for a built 2.56 which is on the expensive side especially when i'm not certain how it'd perform in the end
    Click here to enlarge

  9. #34
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    Let's pretend this is done, what do you guys estimate the ET/trap would be affected by, without wild guesses if possible Click here to enlarge

    60-130 could also improve as it'd be a 2-3 shift not a 3-4 shift...exception being that 2-3 shift is harder to nail fast than a 3-4 (just a straight down pull on the shifter)
    Last edited by dzenno@PTF; 01-26-2012 at 11:55 AM.
    Click here to enlarge

  10. #35
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    It all depends on where you land on the 2-3 shift. Trap wise I think you will be roughly the same, Et wise I think you will be able to knock off 2-3 tenth due to traction in 1st and 2nd.

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    .25 slower ET

    1.2mph slower MPH

    .4 slower 60-130

  12. #37
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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    .25 slower ET

    1.2mph slower MPH

    .4 slower 60-130
    How did you arrive at those numbers?
    Click here to enlarge

  13. #38
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    Steve, I'm surprised you didn't shift into 5th in the quarter mile on those RBs. My car redlines right around 126 with stock wheels and tires.

  14. #39
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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    How did you arrive at those numbers?
    Hatoraid due to his new platform being a pos? lmao j/k, or am I

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    1 out of 1 members liked this post. Reputation: Yes | No
    I was always under the assumption that the 6th gear of the AT was geared much longer than the MT, however the above calculations indicate the contrary...?

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  16. #41
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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    How did you arrive at those numbers?
    just a gut feeling after looking at your an my dyno's done in mph, and SWAG as to what your bests have been compared to my bests, and how much further this will put you back.

    I have a gut feeling that being "in gear longer" isnt what its cracked up to be. think about it, for ET, dragracers alwas go shorter... for 60-130, i could be off, but dont see how when i revert bac to looking at power over mph.

    Click here to enlarge Originally Posted by themyst Click here to enlarge
    Steve, I'm surprised you didn't shift into 5th in the quarter mile on those RBs. My car redlines right around 126 with stock wheels and tires.
    i had the 17's on IIRC, i was VERY high in the rpm when i was setting the record, hell it may have even shifted, i was kinda not paying attention to that, more trying to stay straight..
    now on the 19's, i wasnt as high.. but that gets me thinking now..

    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    Hatoraid due to his new platform being a pos? lmao j/k, or am I
    lol, i was about a month too early in trading out Click here to enlarge

  17. #42
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    0.1s - 0.2s quicker.
    1- 1.5 MPH faster. The power is needed for the trap in the back half and having the full powerband of the 3rd gear makes the difference compared to just getting into the beginning of the power band in fourth.

  18. #43
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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    I have a gut feeling that being "in gear longer" isnt what its cracked up to be. think about it, for ET, dragracers alwas go shorter... for 60-130, i could be off, but dont see how when i revert bac to looking at power over mph.
    I'd bet those drag racers going with shorter gears aren't doing it with manual trannies...with a manual tranny I think taller might be better

    Click here to enlarge Originally Posted by 654 Click here to enlarge
    0.1s - 0.2s quicker.
    1- 1.5 MPH faster. The power is needed for the trap in the back half and having the full powerband of the 3rd gear makes the difference compared to just getting into the beginning of the power band in fourth.
    Is that just a rough approximation or did you use a calculator of some sort?
    Click here to enlarge

  19. #44
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    I reckon up to 130mph your car is going to be great. Slight possibility that third might be damaged power wise. When I moved to the 3.15 from the 3.85 I noticed major drops in the G's on the higher gears especially in 5th. The applied torque to the road drops significantly when you got to pull through so many gears especially when the wind resistance increases at the higher speeds.

  20. #45
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    4.045 compound 3rd gear ratio with 2.56
    4.855 compound 3rd gear ratio with 3.08

    Difference is ~17% in gearing so in 3rd i'd be losing 17% torque applied to the ground with 2.56 vs. 3.08...at these power levels that equates to:

    At the moment in 1:1 gear the car dynos 525wtq currently

    With a 2.56, overall multiplicative torque to the ground through the gearing = 2123
    With a 3.08, overall multiplicative torque to the ground through the gearing = 2549

    Loss of 426 peak torque at the wheels with 2.56 vs. 3.08 in 3rd gear...how significant is this over the coarse of the 3rd gear when translated to actual mph? 17% slower or much less?
    Click here to enlarge

  21. #46
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    I did not calculate it as I'm lazy to search for a calculator especially as you found one. You svould use it. The hand calculation above is meaningless. As well you could conclude that you are using 4th gear with 3.08 and the compounded gearing is a lot worse than with 2.58 which enables using 3rd gear and a lot more torque to the wheels because of that.

  22. #47
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    ^^^ yep, need to graph it out if comparing torques. For example at 110 you'd be changing into 4th with 3.08, but still in 3rd with 2.56... 2.56 would have greater acceleration at this speed. simpler is just to look at the hp per usable rpm range in each gear.

    For 1/4 mile you can use theoretical calcs to determine what's best on paper... trap formulas assume average hp and this could be roughly calculated. The NO gear change would give 3 tenths additional acceleration with the longer gears.

    you can make it as complicated as you want really.

  23. #48
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    The spreadsheet calculator i got in an email from someone here is actually pretty awesome. It allows you to enter in tq+rpm values from a dyno session along with gearing and tire diamater and weight. Then it allows you to see the graphs in terms of optimal shift points for that gearing given the dyno numbers. That's cool and I can do that with my 3.08 final drive dyno as I have all the details and numbers pertain to it. Then you take those same numbers, change the gearing around only, and see how it compares in terms of shift points...just need to get some time to manually enter tq numbers from the dyno chart into the spreadsheet as there's no easy way to export a Dynojet .drf file and get the RPM and TQ columns so I could simply copy them into the spreadsheet. In any case its doable and I think that'd be the ultimate theoretical comparison between the two as a few of you have already indicated.

    I'd share the spreadsheet here if @black bnr32 doesn't mind.
    Click here to enlarge

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    Click here to enlarge Originally Posted by dzenno Click here to enlarge
    I'd bet those drag racers going with shorter gears aren't doing it with manual trannies...with a manual tranny I think taller might be better



    Is that just a rough approximation or did you use a calculator of some sort?
    The N54 auto has the distinct ability to launch in 2nd gear, something you manual guys can't do without heating the piss out of your clutch. Heck, even the C63 can't launch in 2nd Click here to enlarge

  25. #50
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    Click here to enlarge Originally Posted by Laloosh Click here to enlarge
    Do it. Take any factory 125 plus manual car and look ar the gearing. Zo6 come to mind and their gearing is even longer then what you want. Hell if i ever need to drop the pumpkin im doing it.
    That is pretty much what came to my mind.
    Never thought I would see the day...
    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    Life is so much more fun with a nemesis. I miss Shiv. Click here to enlarge
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