How do I get the Corvette to be really sequential?

Discussion in 'General Discussion' started by O11, Jul 2, 2013.

  1. Slamfunk3

    Slamfunk3 Registered

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    From digging thru the ALMS rulebook a while back I was able to find that the GT2 and now GTE cars are allowed a "throttle limiting" form of traction control. I believe that is what the traction control setting in rF2 does.
     
  2. Gearjammer

    Gearjammer Registered

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    One thing to note about the downshifts even on sequential transmissions is that if you downshift too roughly and too close to the limits of your traction, you will definitely unsettle the car as your drive tires will exceed your traction limits. Most forms of racing don't use engine braking for downshifts, especially in the lower gears because of this. In order to soften things down, the shifting is done primarily to get into the right gear for the corner exit and done at the last possible moment, doing otherwise would cause the drive tires to lose traction if the driver can maintain the threshold of braking near 100%. As for upshifts, those are easy to do with or without a clutch as long as you know what you are doing. Take it from an old truck driver, I never use a clutch in a 13 speed transmission unless I am stopped.
     
  3. Guy Moulton

    Guy Moulton Registered

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    V8 Supercars uses a totally different gearbox manufacturer- Albins ST6. So you can't really compare this to the Vette- apples and oranges.
     
  4. 64r

    64r Registered

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    Actually, the F1 comment is incorrect. The F1 regulations allow seamless gearboxes and have done for many years, every team now currently use seamless shift on upshifts, and most also downshift using seamless shifts. The F1 gearboxes are truly seamless in that they engage the next gear before the current gear is released.

    A bit of an explanation with a nice animation can be found at http://www.youtube.com/watch?v=256JWOI1KYQ

    Although the video is nice, it's not technically correct. F1 gearboxes have 2 barrels which are used to engage the gears. When a shift is requested the first barrel is asked to disengage the current gear, however due to the load on the gearbox the gear cannot disengage. About 1ms later the 2nd barrel selects the target gear, as the target gear is engaged, the gearbox is momentarily in 2 gears. As the target gear is engaged, the output shaft speed drops, this removes the load off the current gear and allows it to release. At no point during the shift has a gear not been selected.

    The above all sounds logical enough, but the actually operation is incredible. Both the input and output shafts have trigger wheels on them, the ecu has to calculate the position of both shafts at all times and only fire the valves to change gear so that the dog rings are engaged perfectly, this is difficult to explain, but basically the ecu has a window to aim for to prevent dog on dog changes that will instantly destroy a gearbox (Seb at Silverstone). The ECU has to constantly monitor and compensate for barrel transit times etc all while handling input processing of trigger wheels at 20khz. If this sounds easy enough then remember that the ecu has to handle shifts as the wheels go over potholes, kerbs etc that constantly change the gearbox loadings.

    In terms of changing the shift harshness, the driver (via a dial) can select different shift modes, the fastest mode may be seamless shifts but for the wet it is common to select a mode where a little bit of clutch slipping is used to soften the shift when the conditions are slippery.

    Sorry for bringing this off topic, back on topic, the only seamless geaboxes in the world are F1 boxes so every other gearbox uses a shift that passes through neutral phase (not having a gear always selected) during the shift. Logically, if you try to change gear without lifting (or have the ecu perform a small cut), the load change on the gearbox and final drive (and eventually the wheels) would be a large step and will upset the balance of the car.

    From a real world driving perspective, it is quite common to setup gear rations based not just on optimum lap times, but also on driver usage. For example at some of the tracks we race at we have to compromise some shifts due to the track layout, eg at one track the ideal point for a shift is mid corner, but it's not possible because the shift upsets the car too much. Whilst we cannot change this gear (it's optimised for elsewhere on the track), through testing and analysis we found that it is better to lift slightly off the throttle for the mid corner to exit phase to keep the car off the limiter, then change gear immediately the car straightened up. The other option of selecting the next gear early was tested but we found we would lose a few 10ths by comparison.
     
  5. Minibull

    Minibull Member

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    *Ahem* Except the Honda MotoGP bikes...and hopefully soon Yamaha...;)


    Ohhhh I know, this is about cars...:rolleyes: XD
    Great info though, such a hard thing to figure out
     
  6. Minibull

    Minibull Member

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    So their method of sequential gearbox is different in some way?
    Surely apples and oranges would be looking at paddle shift super dooper fancy boxes in open wheelers and trying to compare them to the Corvette?
     
  7. kaptainkremmen

    kaptainkremmen Registered

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    I was watching something on this a while ago. It is in 2 gears at the same time for 1/4 revolution (of the gear) or less or it will 'explode'
     
  8. 64r

    64r Registered

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    Cool, thanks for the update on that, I had completely missed that, it makes sense for them to use it but I hadn't realised that they were. Too much time spent doing the F1 thing I guess....
     
  9. Minibull

    Minibull Member

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    Is that Yamahas engineers talking?

    All I know is that the shift times are approx as follows (Riders have said the Ducati has always been hard to shift gears with)

    Ducati 42ms
    Yamaha 27ms
    Honda 8ms
     
  10. Guy Moulton

    Guy Moulton Registered

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    Yes, of course. Albins is an Aussie company so theirs is mounted upside down.
     
  11. Adrian

    Adrian Registered

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    And their transmission fluid flushes in the other direction.

    Sent from my Nexus 4 using Tapatalk 4 Beta
     
  12. Dave Millard

    Dave Millard Registered

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    And don't forget everything turns counter clockwise.
     
  13. lbird

    lbird Registered

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    Technical terms explained for everybody. I just love that ;)
     
  14. O11

    O11 Registered

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    NOOOOOOOOOOOOO!!!!!! FUAAAAAARK!!!

    I am wrong... and I'm not used to that. XD
    Learn every day... thanks guys.

    So the thing is that the "virtual arm" is not pulling the lever briskly enough? And that's why the upshifts are rough. Wish it was faster.
     
  15. Minibull

    Minibull Member

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    Effing A man, that is almost a first for me on this forum, i kid you not. Someone reacting like a rational and level headed adult XD


    But who knows with the Corvette. I would probably go under the style of thinking that ISI know what they are doing with the actual car itself and they way they "built" and modeled the transmission, but maybe they haven't fully sorted all the shifting options and settings with the actual game. I think that if a car has a sequential box and some kind of quickshifter, that should be built into the car ingame, not set outside the game in the PLR.
     
  16. Armando

    Armando Registered

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    But auto-blip and auto-lift ARE built into the car.
    The options you can find in the PLR are global options you can use to override the car setting when it does not have the option.
    For example, if a car does not have auto-blip but you activate it in the PLR, you will have auto-blip.
    Not the other way around, if the car does have auto-blip you cannot deactivate it.
    It is related with auto-clutch, too. But I don't remember if it works with auto-clutch activated or deactivated. :confused:

    This is what I understand from my tests and what I have read about it. It could be partially inexact. :D
     
  17. Marek Lesniak

    Marek Lesniak Car Team Staff Member

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    I am more into older GT spec cars (like 2005-2010) and not that much ALMS but rather FIA GT - both older GT1 (Saleen S7R, F550 etc.) and GT2 (997 GT3 RSR, F430 GT2) had sequential mechanical dog staright cut gears gearbox. In most of them, there is a load cell sticked to lever or somewhere in the gearbox to detect, that a driver wants to change a gear. That's the signal for an ECU to cut ignition for a given time (100ms or maybe slightly more). No ignition during gear change means, there is no load coming from an engine but still, a driver has to do the change as fast as possible (gentle pull/push will do more harm for dog teeth than a quick and sharp move). With downshifts, a driver does not neccesarily has to use clutch. Gear changes could be done without it, but with more risk of slowly damaging gearbox. That's why clutch is used on downshifts - to keep gearbox in good shape as long as possible and also to smoothen downshifts too as even with very fast clutch operation, there will always be some slip which dampens load a bit.
    As far as I know, rF 2 still doesn't have proper gearbox model. You can't enable auto lift and keep semiautomatic=0 and that's what we need for some cars, including the Corvette GT2. Such combination could allow you to have upshifts done without tyre slip (no torque coming from engine during gear change) and in the same time - force you to be gentle on downshifts (so, use clutch whenever possible).

    GT3 is a different story though . Of course, they still use racing straight cut dog gearboxes but there is more electronics involved to make GT3 spec. race drivers' life easier ;-) They have ABS, TC (which was not allowed in older GT1 and GT2...damn, I miss those times so much!) and both auto lift AND auto blip (see, tech. spec for the 997 GT3-R 2010 and never for example).
     

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