Short shifting

Discussion in 'Gran Turismo Sport' started by Whiteshark90, Jun 9, 2018.

  1. Whiteshark90

    Whiteshark90

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    Hi guys, since I bought a g29 I'm using manual shifting.
    I've tried to save fuel since then by short shifting but I'm not sure I've got it right.
    Basically you shift a little before you normally would in order to save fuel, right?
    So my question is at how many rpm you should shift to optimize fuel save without losing much speed.
    How much you should gain by short shifting?
    Thanks in advance and sorry if this is a double post but I couldn't find one precisely talking about this topic.
     
  2. GT_Alex74

    GT_Alex74

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    It all depends on the car. Just check your power curve in car settings (put the cursor over the power adjuster and it will show up). Some cars are better suited for that than others.
     
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  3. Whiteshark90

    Whiteshark90

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    So the X axis is the RPM while the y axis is the speed, the optimal time to switch is when the values intersect, am I right?
     
  4. AlexLion

    AlexLion

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    In general, if you’re normally changing gear on the limiter (when the rpm bar becomes blue and flashes), to have effective short shifting I tend to shift when the bar is about halfway. That way you don’t lose too much speed while still saving a bit. It depends on how much you want/need to save though
     
  5. Hoopzah

    Hoopzah

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    The more torque, the better the vehicle is equipped for short-shifts.

    Vehicles where max torque is produced at 7.5k+ rpm aren't the best choices.
     
  6. phil_75

    phil_75

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    Do a fast lap in the Gr3 Viper using max revs then when you have a ghost car shift when the rev meter is less than halfway and you will see you can easily keep pace with your ghost whilst using much less fuel.
     
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  7. GT_Alex74

    GT_Alex74

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    Well, the Gr.3 Viper is actually faster when you short shift it a bit. You should never use max revs with it.
     
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  8. rex1825

    rex1825

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    511
    ...if looking at the bar, you should always shift at about 2/3 with Viper.
     
  9. rex1825

    rex1825

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    As some already said, it all depends on the car that you are driving, for some short shifting isn't going to help at all, since they will probably have low torque (usually high revving engines).
    For some you'll get a lot out of it, especially diesel engines that have really high torque.

    In picture below, peak torque and peak power is where you should utilize short shifting, closer you go to peak torque, more fuel you will save, closer you go to peak power, faster you will be.
    In this picture, perfect shifts would be anywhere between 5500-6000rpm, anything over 6000rpm is only going to use more fuel, but you won't get much out of the engine, and for short shifting it would bee good anything between 4500 up to 5500rpm.

    [​IMG]


    One example of diesel car that I am using as LMP2 in one event. Peugeot 908 HDi FAP with 490hp and 930kg.
    It's redline is at around 6500rpm, this is where AT is shifting.
    When shifting at 6500rpm car can go apporximate 410km on one tank.
    If I reduce shifting to 6000rpm, I get 60km more range (470km) and also faster times, since this engine looses a lot of power after some 6200rpm.
    If I reduce shifting for another 500rpm, to 5500rpm, I can go even further (535km) for almost same times as if I would shift @ 6000rpm
    Power and torque curve for 908 are ideal for short shifting and gaining time and speed...

    For example M6 GT3, you can short shift it, and you will gain a lot of fuel, but you can also red line it, it will do just a bit better times when pushing engine in high rpms.
     
  10. Whiteshark90

    Whiteshark90

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  11. phil_75

    phil_75

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    Wouldn't ~3700rpm be a good place to shift?
     
  12. Vegard

    Vegard

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    No.

    Sure, you'd save a lot of fuel but you'd lose too much time that way. Shifting so that you "land" at peak torque would be a better compromise between acceleration and fuel saving.
     
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  13. Macboyilija

    Macboyilija

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    True for more cars I think. Also sometimes lower gear exit of corners gives higher end speed up to next corner. You can learn this by watching replays of the top 10.
     
  14. rex1825

    rex1825

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    511
    ...nope, you'd loose to much of acceleration.

    Torque is moving the car, power is accelerating it, so you need to balance those two.

    Also I forgot to mention for that picture, from 3500 to 5500 is ideal for engine rpm's to be, so basically when you upshift, doesn't matter if you are short shifting or pushing it, you should always have engine rpm's in that segment... this way it will give you most...
     
  15. Vegard

    Vegard

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    Torque accelerates the car. If you look at acceleration thrust curves you'll see that they're re-scaled versions of the torque curve.
    Power is just a way of analyzing torque, more specifically it measures the rate at which work is done (by the torque).
    Ideal for fuel economy or acceleration?
    The most what?
     
  16. vxr58

    vxr58

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    I honesty think you’re better off using fuel maps. Being in the wrong gear confuses me and I inevitably mess up.
     
  17. SjefGielen

    SjefGielen

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    Wow, this was good reading! I always rev up until the RPM meter starts flashing, feels a bit stupid now.
    Okay, can someone who really understands the physics behind all this explain to me what would be the fastest rpm count to shift in the Ferrari Gr4 and Gr3 cars? I really need to shave off a few tenths per lap to get me from seeing P1 to P3 slowly pulling away to keep up with them!
     
  18. Vegard

    Vegard

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    It's over 9000!

    Seriously though, both cars will be fastest when shifted slightly past 9000 rpm.
    As a general rule you want to shift up when the next gear has more power available than the current one.

    For most cars the shift light is pretty much spot on.
     
  19. SjefGielen

    SjefGielen

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    OK, so when I need to be as fast as possible, shift as soon as the light bar is full and starts flashing, and shift earlier if I need to save fuel.
    Thanks for this, shifting earlier really helped me in yesterday's daily race C, I could make the fuel last 11 laps, while earlier I had to refuel after 9 or 10 laps.
     
  20. Tristan Jones

    Tristan Jones

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    Location:
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    Same as I do Phil, surely thats the only real way to test it properly...

    Some good info here all...good read...

    Just to add my 2 cents - Most cars benefit from shortshifting, but the most powerful cars also benefit from coasting. Lower cars gain little from coasting, but when racing Gr1, try doubling your braking zone and coasting a little past your usual braking zone - you gain a lot, though only small gains are made when doing this in smaller cars. I hear the hybrids gain from this too, charging their battery while coasting, and using it to accelerate out of the corner.

    The other benefit to shortshifting is turning - as it can save fuel, you can get a double benefit by shortshifting on corner exits and getting full throttle on earlier, using torque to build speed quicker than a reduced partial throttle due to wheel spin.

    Someone correct me if not correct, but I heard you don't want to shift too high mid corner because you will land in the next gear at max power and spin wheels.
     
  21. BigJimmy

    BigJimmy

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    Has anyone done a fuel maps versus short shift analysis?
     
  22. KinLM

    KinLM

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    Why not do both?

    If you really wanna save fuel, drop down a couple fuel maps so you won’t be spinning away your tires (and thus fuel) on the exits of corners as easily while still being able to stretch the lower gears out, and then at the ends of straights, short shift from 4-5 or 5-6 since you’ll be braking before too long anyways and time losses will be minimal.

    While you’re at it, do some coasting at the ends of straights too. Especially if you’re in a higher gear with less engine braking.

    I use all these methods on the 60 minute LM Group 1 endurance race with the TS050 and I can go the entire length of the race without making a pit stop.
     
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  23. Bruunz

    Bruunz

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    The bar flashes when peak power is reached and not red line. If you look carefully this can before or after red line depending on the car.
    It's also ideal to look at the curve before and after peak power. Is there a major rise or drop off near peak power?

    To all torque vs hp comments. You want to be referencing hp as it is more relevant. HP is a result of torque.

     
  24. Vegard

    Vegard

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    No, you're quite wrong about that.

    I can see how you'd make that assumption as the typical car in GTS produce peak power 500 rpm before the limiter and the redline is often set at, or slightly past that rpm.
    But check out the Gr.3 Corvette, the Supra GR RC or the Alpine VGT RM to see how wrong you are.
     
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  25. GT_Alex74

    GT_Alex74

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    Actually no, short shifting is more fuel efficient than fuels maps for similar lap times. At least that's my experience from several endurance races. An example : 1 hour endurance on Maggiore GP in a stock 911 GT3 RS. I did full stints in practice to compare different strategies, and shifting at 7000 - 8000 rpm around the whole track was like map 2 in terms of lap times while being map 2.5 in terms of fuel savings (a more than map 2 but less than map 3). I ended up winning the race doing one less pit stop than everyone else while still scoring the fastest laps.

    But I think the main advantage of short shifting is you can adjust easily in different parts of the track, eg just short shifting in technical parts, or just short shifting at the end of straights tostill benefit from good acceleration out of corners. You can do that with fuel maps as well of course, but all the manipulations you have to make take some time and are a potential source of mistakes. Switching from short-shifting to full revving is instantaneous.

    Note nothing prevents you from combining short shifting and fuel maps, and and lift and coast over that. I did all of that in a Gr.2 endurance on Suzuka : full revving up to 4th gear after Spoon, short shifting everywhere else, lift and coast before 130R, chicane, Degner and T1, going through the esses in 5th gear, and putting map 6 through the esses for one or two laps each stint to get me the last droplets I needed. Map 6 would have been 4 or 5 seconds slower; with this, I was able to score times within a second of my qualy time, down to half a second slower only. And it's not that hard to do, just practice it a bit beforehand and you won't mess up because of it.
     
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  26. vxr58

    vxr58

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    Thanks for the info, really helpful re GR.2 strategy.
     
  27. GT_Alex74

    GT_Alex74

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    Well, this was really specific to particular lobby settings (fast fuel depletion, low tyre wear). Sports races, most of the time you're not going to avoid a pit stop and gain time from it in the end. You'll still want to save some fuel if you can, especially if stuck in the pack, to shorten refueling time, but I wouldn't use fuel maps at all and probably short-shift less.
     
  28. Bruunz

    Bruunz

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    I dont actually understand your comment. Are you saying that the bar flashes at the limiter or somewhere else other than peak or just 500rpm before redline?
    Sorry im at work and cant look at the graph.
     
  29. Vegard

    Vegard

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    The point of my comment was that the bar doesn't flash when peak power is reached.
     
  30. Mirror_man

    Mirror_man

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    Always?? Sometimes?? Never???? So... when does it flashes???