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When to change gears?

Discussion in 'RACE 07 - Official WTCC Game' started by Marco Boemi, Jan 27, 2010.

  1. Hi all, first post here. Probably a stupid question but anyway...
    So, when is the best time to change the gear? In the tips is said to change when the gear become red but this is really close to the rev limiter. Also on a setup guide a read is written to change at the max bph which in Race seems to be when the tachometer become red. :eh:
    What's the truth?

    Thanks for your help.
     
  2. Depends on the car/engine, you get the best acceleration when you shift at the peak power which doesn't necessarily mean to shift at the redline. Take a look at the power curves here
    http://www.racedepartment.com/downloads.php?do=file&id=2254

    Sometimes its faster to stay longer in gear before a turn, then to change a gear (losing time in gearshift), sometimes its better to upshift before the power peak, this make sense for the lower gears where the traction limits most and you need a good traction and weight distribution through the turns. If only the air friction comes into play (long straight line) you should shift at the max. power, because you can gain there at most. You have to fine tune the gearbox in a fine compromise to get the best acceleration between the important turns and decent drive in other parts of the track.
     
  3. That's a common misconception.

    As you can see in the torque curves you linked to, when you shift up your revs will go down and the engine will be outputting a different amount of torque at the new rpm (usually higher torque since you perform the shift usually very late in the curve).

    One other thing that will definitely happen is the transmission's torque multiplier will go down (on upshifts) due to the new gear ratio. This means that even if the torque curve was constant in the range from the old rpm to the new one, you will be transmitting less of it to the tire. See formula 11 at Brian Beckman's Physics of Racing series (excellent series btw).

    So the combined effect of these two contributions in opposite directions determines whether you should shift up at any time before the rev limit. Depending on the torque curve and gear ratios, if there is an optimal shift point, it may be pretty much anywhere (and this is why real world shift indicators can be programmed to separate rpm values for each gear). If the torque curve doesn't drop much at the end with respect to the gear ratio change, there may not even be an optimal shift point, i.e. you'd want to get as close as you can to the rev limiter before shifting up.

    This still doesn't answer when you need to shift up in Race because a) (most of) you don't have the torque curves and nobody should study rpm gauges that intensely while driving and that's why shift indicators exist, b) in-game shift indicators are sometimes rather weird (see the notes file among the charts) and there are too many of them (e.g. drive the WTCC Chevy from the cockpit: first the HUD's rpm gauge's inside circle will turn red, then the red led on the car's dashboard will turn on, and then the gear number on the HUD will turn red.). In other words, I don't know.
     
  4. Try to shift as late as you can, UNLESS you have really close gears and when you shift up you end up above peak revs (ideally you want to shift to bellow peak revs, so you get as much of a gain as you can), although that is fairly uncommon.
     
  5. I.. just shift at the redline. :)
     
  6. Bram

    Bram
    Roaring Pipes Maniacs | #27 Staff Premium Member

    I shift as late as possible. Mate Yoeri though shifts much earlier, drives the same laptimes and above all consumes less fuel per race then i do :(
     
  7. What a surprise. I thought my question was very simple and that there was a single moment that all the pros use to change the gear. I know and I use shortshifting when needed, my question was about when to change in a long straight line. There are some very articulated answers here which probably I didn't understand completly . Btw thanks all. More answers are wellcome. My idea is that in ideal conditions (gears setup correctly, straight line, etc) the right time to change gear is just above the max power. Now I have to verify if this correspond to the red line...
     
  8. Bram

    Bram
    Roaring Pipes Maniacs | #27 Staff Premium Member

    Its actually a really good and interesting question!
     
  9. Your question is oc interesting, also it has been answered in the past with great detail in the forum, I just can't find the post (new forum).

    So without going all over it again, I will post here the kind of "conclusions" that old topic explained & cleared regarding this matter (at the time with a small contribution from me, big contribution from some else I don't remember who).



    1st something that is obvious but I just post it for the sake of clarity; regarding circuit racing, if the wheels are spinning, or the car is moving sideways, obviously it isn’t moving forward as it should, so at least theoretically you are “losing” time (that is why you might short-shift like you typed for instances).


    In RL regarding competition engines, especially in our electronic age, there are many times several engine mappings to choose from. How an engine behaves depends on many things; its geometry, its alimentation, its ignition timings and so on…

    Simbin approach was to make 95% of all Evo content “screamers”… as more rpm you pull more hp it gives. In other words, in most cars in the Race series, the hp peak is coincident or very near to the rpm limit.

    One thing has to be clear, hp "makes" the car go faster, higher the hp, theoretically more the car moves forward (not “that important” in old school rally for instances, but important in circuit racing). The torque is important to carry weight and “sustainability”. Meaning, for the lorry or your everyday car you want torque together with what we may call a square engine (torque peak near hp peak and broad power band) as it gives you drivability, all you need to travel and go to work (that is one of the reasons why so many people in Europe love the turbo diesel engines).

    At first approach, in racing, all you want theoretically is hp, the more the merrier… ;)

    Theoretical rule (very important in our short race sim-world): Basically you only change gear when you will gain hp with that change.


    Let’s look at the GTS M3 curve (a typical RACE series curve).

    BMW M3 GTR.PNG

    • You change gears at the limiter (near 8500) because at that zone there is already a lower rpm zone where there is more hp available (let’s say you change from about 8500 to 7500). Ok?

    • Some of you might have thought that changing at peak hp would be better (about 7900rpm), but it isn’t … If you change gear at 7900, your engine drops rpm, let us say to 6900, and you went from high hp to low hp, it would have been better to keep the rpm climbing instead of changing gear.

    • Even “worst” option is the old lorry driver option, let’s change at the torque peak (about 6300 rpm), not only you are at a much lower hp zone but also with the rpm drop you go to a much lower hp zone in this “peaky” engine. Obviously this zone (let’s call it in this engine the torque zone), is where perhaps you want to be if your wheels are spinning, the car isn’t moving forward and you need more traction than hp (a car isn’t more that the physical balance between traction and movement).

    The M3 is a good all-around race series typical car, but… there is the exception, the Corvettes. Let’s us look at the GTS C6 curves:

    Corvette C6 GT2.PNG

    • Here you can change at 6200 rpm (where you are already losing hp) and drop to 5200 rpm where not only you are at peak hp but will also be at peak for the next 1000 rpm… there you have it, the long distance runner of EVO (C6 & C6R). On top of that see that torque curve, 2x times more almost than the M3… if you “taxi drive” the C6 you are ok as the hp peak is about there, if you “taxi drive” the M3 you are almost using only ½ of its engine hp :7:
    There are a few cars that are in between these 2 examples, one that comes quickly to the mind is the Vipers… but you can "play" that same analysis to any of the engine curves presented here by Tobias.


    So in short, "RACE series sim-racers of the world", in sprint racing (most races you all do) shift as late as possible without care (unless you are using a Corvette), if available higher that rpm limiter and change when the red light is about to go intermittent (just a split second before you hit the limiter). It is a short race, it is a game, it doesn’t matter, murder that engine…

    Of course if your traction wheels are already spinning in the same place, there is not much point in keeping the power as what you desperately need in such situation is traction… so you guessed, you short-shift (for instances), lower your hp saving fuel and actually moving the car faster forward since in such situation you needed more traction than hp (common situation in WTCC & STCC cars).

    Now, obviously in RL the things aren’t like that as competition car costs more than your house, so when that engine goes from better to worst, nobody directly involved will be happy…​
    In the RACE series the only way for engine live/management come into equation is with endurance racing (above 120, 180 or even 240 minutes). In that situation the “change always at the limiter” option can’t be used all race or the probability of engine destruction goes higher and higher (like in real live, there is a game variable that multiplies X rpm with t time… so an engine has X * t durability, more rpm you pull, less time you will have with your engine).


    Ok, long post, sorry if this didn’t come out so clear as I would have liked but I was trying to say much as quickly as possible… anyway, hope it helps :)
     
  10. If you suspect that you may be shifting too soon/late, you can compare longitudinal acceleration values in Motec right before and right after the shift. If you didn't botch it completely, they ought to be quite close. Though you can't tell if you really nailed it because there is a lot of vibration, slight changes in ground speed before and after the shift, etc. and Race produces intelligible motec logs only at a puny 10Hz.
    MotecG.png
     
  11. Thanks all especially João Andias, your post cleared all my doubts.