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Shifting Point - What is optimal RPM to shift?

Discussion in 'Tracking, Autocross, HPDE, Drifting' started by nibble, Aug 1, 2020 at 10:46 PM.

  1. nibble

    nibble Well-Known Member

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    A90's red line is 7,000 RPM (Orange starts at 6,500 RPM) but looking at dyno chart, power peaks at 4,750 RPM and falls to ground at around 6,400 RPM.

    toyotasupradyno-1559240377.png

    when do you shift to get optimal acceleration?
     
  2. Bflood

    Bflood Member

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    I think most people throw it into auto after launch. Figure the computer would know best..
     
  3. OP
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    nibble

    nibble Well-Known Member

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    computer is reacting to input I give, where when I shift, I anticipate and what RPM it should be for entry and exit of the corner. although I could have it auto on straight, I will have hard time switching between auto and manual consistently... BTW, on highway, computer switched gear at 7,000 RPM where it fell to cliff on dyno chart.. not exactly optimal switch...
     
  4. YungMercureal

    YungMercureal Well-Known Member

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    It's not necessarily a straightforward answer, any hard accel you're going to blow through gears up to 3rd anyways. The answer is also going to depend on available traction, are you going in a straight line, etc. Also I wouldn't trust just one single dyno chart. The redline is at 7k, that's where the engine is cutting fuel or spark. You could check the sport displays to see if you are losing power before the up-shift at 7k.

    To be brutally honest, I don't think optimizing shifts is going to matter unless you're actually going fast enough to use 4th and up. At that point the gear is long enough that you would probably want to make sure you shift into the power band.

    Engineering Explained has a good video on this topic if you are actually interested in the math behind it

     
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    nibble

    nibble Well-Known Member

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    Well.. I do shift the hell out of my S2000's at 8K & 9K (I tracked both AP1 & AP2) and it does have right feeling, same for NA & Supercharger. acceleration was consistent and reliable - more like.. expected.. However, say for example, lightning course in NJMP. Coming out of light bulb, I'm already on 4th and after shifting at red line to 5th, over 100 mph, but reaching to 130~140 mph, it feels like it's not accelerating as hard as expected. In case of 240sx race car, it was better to up shift around 5~6,000 RPM rather than the Red line because power fell beyond 5,000 RPM and it wasn't accelerating. Hence, I'm trying to see if I should shift early like 4~5,000 RPM to get maximum torque at 2,000 RPM on next gear or somewhere around 6K..
     
  6. YungMercureal

    YungMercureal Well-Known Member

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    I get what you're saying. I'd have to recheck, but I think I tend to shift around 6500 and it drops into the torque band pretty well. I'm not doing any HPDE though, so I would say I have room to improve.
     
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  7. Supraboi7

    Supraboi7 Well-Known Member

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    You don’t have to worry about it, the automatic transmission will shift for you.
     
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  8. Marin@GoodSpeed

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    This heavily depends on what you are doing. Sometimes the extra heat of staying in gear is ideal, sometimes going up a gear in preperation is ideal. On the factory calibration 6300-6500 is the ideal shift point for most cars. Once you tune the car on race fuel this can sway quite a bit as the horsepower can peak earlier if you leaning on the turbo hard. When you are going for sheer acceleratoin the average HP over the time you are accelerating is most ideal. And considreing how flat the HP curve is if you shift at 6500RPM you will land on that flat spot in quite a few gears, or just below it.
     
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  9. OP
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    nibble

    nibble Well-Known Member

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    Your explanation makes much more sense.
     
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