Shifting Rpm's
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Cadillac ATS General Discussion Forum Discussion, Shifting Rpm's in Cadillac ATS Discussion Forums; Question? Not having driven a manual for many a year and certainly not with a modern car like ATS, when ...
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    redsoxski's Avatar
    redsoxski is offline Cadillac Owners Fanatic
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    Shifting Rpm's

    Question? Not having driven a manual for many a year and certainly not with a modern car like ATS, when shifting into 2nd as well as 3rd gear, what are the optimum rpm's to shift for each of these gears? Just love the manual in the 3.6 Performance for both acceleration and roar of engine.

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    Bertha D Blues is offline Cadillac Owners Fanatic
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    Re: Shifting Rpm's

    3.6 with manual?

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    Hoosier Daddy's Avatar
    Hoosier Daddy is online now Moderator
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    Re: Shifting Rpm's

    Quote Originally Posted by Bertha D Blues View Post
    3.6 with manual?
    I'm pretty sure he's talking about using the auto in manual mode.

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    ben.gators is offline Cadillac Owners Connoisseur
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    Re: Shifting Rpm's

    A simple, but not very accurate answer is at peak torque points. The accurate, but complex answer is shift at points that the combined area under the torque curves is the largest. That needs plotting torque curves for different gears.

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    JavaGirl is offline Cadillac Owners Fanatic
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    Re: Shifting Rpm's

    Quote Originally Posted by ben.gators View Post
    A simple, but not very accurate answer is at peak torque points. The accurate, but complex answer is shift at points that the combined area under the torque curves is the largest. That needs plotting torque curves for different gears.
    Well, it is more complicated than that, right? Don't you also have to factor in how many tenths of a second you spend at a particular RPM in a certain gear? For example, if all you were trying to do was maximize the area under the curve, you would hold first gear (actually every gear, for that matter) to redline before shifting. Isn't there a point of diminishing returns beyond which your acceleration (what you are really after) is minimal if you stay in the lower gear longer even with high RPMs? That is, isn't acceleration maximized with the higher gear ratio of the next gear even though you have to sacrifice some RPMs/torque to get the higher gear ratio?

    What about shifting to a higher gear when you feel the car starting to somewhat release you from the back of the seat (acceleration starting to drop) or at redline, whichever comes first?

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    Hoosier Daddy's Avatar
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    Re: Shifting Rpm's

    Quote Originally Posted by JavaGirl View Post
    Well, it is more complicated than that, right? Don't you also have to factor in how many tenths of a second you spend at a particular RPM in a certain gear? For example, if all you were trying to do was maximize the area under the curve, you would hold first gear (actually every gear, for that matter) to redline before shifting. Isn't there a point of diminishing returns beyond which your acceleration (what you are really after) is minimal if you stay in the lower gear longer even with high RPMs? That is, isn't acceleration maximized with the higher gear ratio of the next gear even though you have to sacrifice some RPMs/torque to get the higher gear ratio?

    What about shifting to a higher gear when you feel the car starting to somewhat release you from the back of the seat (acceleration starting to drop) or at redline, whichever comes first?
    What Ben said is correct. The easiest way to achieve what he said is: take the wheel dyno numbers for every RPM and make a graph for each overall gear ratio. Basically multiply by gear ratio and plot against MPH instead of RPM across the bottom. The best shift point for acceleration is where the lines cross for two gears, or redline, whichever comes first. In lower gears its usually NOT at redline or peak anything and it will be at different RPMs for each gear, but as the gear ratios get farther apart, the lines often stop crossing and redline becomes the best shift point. That is how to get maximum acceleration. Of course, those points will vary slightly based on conditions because the car's power curves will vary somewhat under conditions.

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    ben.gators is offline Cadillac Owners Connoisseur
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    Re: Shifting Rpm's

    Quote Originally Posted by Hoosier Daddy View Post
    What Ben said is correct. The easiest way to achieve what he said is: take the wheel dyno numbers for every RPM and make a graph for each overall gear ratio. Basically multiply by gear ratio and plot against MPH instead of RPM across the bottom. The best shift point for acceleration is where the lines cross for two gears, or redline, whichever comes first. In lower gears its usually NOT at redline or peak anything and it will be at different RPMs for each gear, but as the gear ratios get farther apart, the lines often stop crossing and redline becomes the best shift point. That is how to get maximum acceleration. Of course, those points will vary slightly based on conditions because the car's power curves will vary somewhat under conditions.

    For NA 3.6L, there might be (and will be) some gears that the curves don't cross and redline is the best shift point for that gear. But in out Turbo engine with factory tune, I wouldn't be surprised if the curves always cross each other, because of the plateau in our 2.0L T's torque curve.

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    redsoxski's Avatar
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    Thread Starter
    Thanks to all for reply. What Javagirl said resonates with me.... It maybe best by sound and feel, especially in lower gears. Who knows maybe CUE one day will provide a light or vibration under seat to shift! Happy Motoring.

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    JavaGirl is offline Cadillac Owners Fanatic
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    Re: Shifting Rpm's

    Quote Originally Posted by redsoxski View Post
    Thanks to all for reply. What Javagirl said resonates with me.... It maybe best by sound and feel, especially in lower gears. Who knows maybe CUE one day will provide a light or vibration under seat to shift! Happy Motoring.
    Thanks, but what I said was not the correct answer... I get Hoosier Daddy's explanation, but unless someone provides such overlaid graphs, I don't think we have much choice but to just guess.

    By the way, redsoxski, you are a female, too, right? I think I remember you saying that on another thread. I'm sorry if I am making a mistake on that. Also, you may be interested to know that I went to college in Boston. I am not a huge sports fan, but I do like for Boston teams to do well. For example, although I have not watched any of the games, I do hope the Red Sox win the World Series.

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