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Model S Performance Launch Feature

Discussion in 'Model S' started by CapitalistOppressor, Jul 7, 2012.

  1. CapitalistOppressor

    CapitalistOppressor Active Member

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    #1 CapitalistOppressor, Jul 7, 2012
    Last edited: Jul 7, 2012
    I posted something about this in the Model S Performance vs BMW M5 thread, but decided it probably deserves its own thread.

    I have heard nothing about an MSP launch mode/feature. Does anyone know anything about this? Regardless it's easy to speculate as to what would be possible with Model S.

    First, a key problem in drag racing with ICE vehicles is that performance varies widely with altitude, humidity and temperature. Many of these variables either don't matter at all, or likely have much less effect on MSP performance metrics.

    For MSP a launch controller could directly measure track conditions and modify its performance curve to optimize launch speeds. Existing traction control software could easily be modified to check current traction conditions by blipping the motor and measuring the force needed to break the tires loose, controlling a burnout to raise tire temp to ideal ranges (verified by same IR sensor measuring track temperature?) and adjusting brake and power inputs to keep the car controlled during burnout.

    The data gathered would generate an ideal launch performance profile/acceleration curve that can be applied at launch.

    The software itself would consist of a new password protected app on the console, which would bring up options for launch/burnout along with performance data for the run, with a button to e-mail yourself the detailed metrics when the run is complete.

    Once you enable the launch sequence, you can perform an optional burnout for the purposes described or choose a fast launch option. Either way, once you are prepared to stage the brake and throttle controls would be slaved to the computer. Staging is accomplished with a rocker switch on the left side of the wheel which can edge the car forward and possibly reverse (after a burnout for instance).

    Once staged, depressing the throttle activates the launch sequence.

    The car locks its brakes and (optionally depending on what works best) torques the drivetrain (meaning the motor is putting out power while the brakes hold the car in position).

    You launch on green by pressing the right rocker switch on the steering wheel. Optimal acceleration curve with optimal traction control (it might be faster to spin the tires some) engages and continues to execute a launch routine until throttle is released or brake is depressed, at which point controls default to normal operation.

    The idea being to consistently get the fastest possible track times. Dragsters routinely use many tricks like these (some illegally depending on class :smile:). The fastest solution should be available, and the app can allow you to disable features features if they conflict with race rules.

    The real advantage with MSP is the electrically controlled precision with which all of this can be accomplished. ICE vehicles have less control over critical environmental variables, and its harder to precisely adjust your power curve.

    MSP Launch Control™ Patent Pending :tongue:

    EDIT: edited for brevity
     
  2. Jason S

    Jason S Model S Sig Perf (P85)

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    Solving a problem that doesn't exist?

    Isn't the whole magic of BEV that the batteries just simply let the car go at full capacity right away? Track conditions have nothing to do with it.

    Burnout: turn off traction control. Non-burnout: turn traction control back on. Best launch: traction control on. ... I don't see any other options required.
     
  3. CapitalistOppressor

    CapitalistOppressor Active Member

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    #3 CapitalistOppressor, Jul 7, 2012
    Last edited: Jul 7, 2012
    Actually, most of the benefit comes from moving the staging and launch controls to the steering wheel. It might surprise you, but your foot is not a precision instrument. The amount of time it takes you to mash the throttle is substantial when you are measuring hundredths of a second intervals.

    Optimal traction for normal driving vs a controlled launch can be completely different. Additional tirespin can actually help you on a launch, though that is something that needs to be empirically determined for MSP under different conditions.

    The other point of an app is to gather data and e-mail it to yourself. Racers obsess over this sort of thing.

    EDIT: Beyond the travel time it takes your foot to depress the throttle several inches, the neurons leading from your brain to your leg have a farther distance to travel than they do to your fingers. Drag racers know this and routinely use a hand control for launch. Main exception being where nostalgia rules prohibit it.
     
  4. Jason S

    Jason S Model S Sig Perf (P85)

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    Ah, I was hoping we'd be able to get the logs easier than the Roadster folks do. That would be cool.

    Didn't know about optimal settings for traction control. Being able to dial in the amount of slip before it kicks in would be a nice feature.

    Staging and launch controls... I'm tracking an adjustable TC slip and the ability to turn TC off altogether as the adjustments needed. Neither are that time sensitive.

    What are you thinking for additional launch controls? Maybe the car checks the lights and mashes the accelerator automatically? (If they haven't made that illegal for drag racing, they definitely should. The tech is there today.)
     
  5. CapitalistOppressor

    CapitalistOppressor Active Member

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    Checking the lights would be out of bounds, and is illegal in every rule book I know of. Of course people cheat.

    I know from experience that additional spin can help a launch. Not always though (it seems to depend on the car). I think the reason is that spinning tires are a way to store momentum beyond what the motor can provide (at say 15mph) which translates into additional forward acceleration when the tires finally hook up. It's very car dependent and probably is affected by traction variables as well.

    Thats why I think it would be neat for the car to estimate it in real time and provide an optimum solution. A loose track (or city street with gravel) would probably like additional traction control (less spinning), vs a sticky track that lets you hook up nicely. It's something that you run a lot of tests for ahead of time and program into the software.
     
  6. stopcrazypp

    stopcrazypp Well-Known Member

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    I don't think the feature of detecting the light and mashing the accelerator is helpful for 0-60 or 1/4 mile times. That will eliminate your reaction time, but doesn't help the other two numbers.

    I think what CapitalistOppressor wants in a "launch control" in his second comment is to eliminate the delay from a person mashing the accelerator. Your car starts to move, but there is a delay from partial throttle to full throttle (since your foot has to move in a range of motion against the resistance of the pedal). A simple launch control for an EV would apply full throttle instantaneously from a release of the brakes or a press of a button, to eliminate that lag.

    As for his original post, I think he wants something like a bi-directional telemetry in F1, where you can program the engine (motor in this case) to optimize itself according to the specific track. I think something like that is a bit overkill for a street car like the Model S though.
     
  7. CapitalistOppressor

    CapitalistOppressor Active Member

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    I admit that a detailed measurement and custom acceleration profile might be overkill for Model S. But it should be easy and inexpensive to program compared to an ICE vehicle, because the motor is entirely electric and should have vastly fewer variables to account for, while offering unparalleled precision control and modulation of power output. If a program like that can subtract a tenth of a second from 0-60 times it would be worth it. If not, then not.

    My initial thought for launch control are the basic features of controlling launch and staging from the steering wheel, while giving an option to e-mail the run to yourself over your 4g network. An optimum power curve still needs to be programmed, but it might be a single hard coded curve rather than a custom calculation. I've worked crew at drag races many times and we obsess over this stuff between each round. But I'll be the first to admit you care more about it when your competition is doing 5 second quarter miles than when they are taking 13 seconds :)
     
  8. CapitalistOppressor

    CapitalistOppressor Active Member

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    Another issue that the software addresses is that there is a certain amount of slack in the drivetrain. Applying power to the motor doesn't instantly translate into wheel movement, even on Model S. On an ICE vehicle this slack is very substantial (there are literally hundreds of moving parts, all with some slop). It is less of an issue on an electric vehicle, but there is still play in the differential and CV axles.

    By applying power to the motor you can take this slack out, while holding the car in place with brakes. The ideal is to apply the maximum power without moving the vehicle, so that when you release the brakes you get a quicker response. It's possible that the time savings on Model S wont justify the effort on this front, but they are a big issue on ICE vehicles. If it can shave 5 hundredths off of your time, that is probably worth it when tenths matter.

    Its also extremely simple to program this into a launch control app.
     
  9. Jason S

    Jason S Model S Sig Perf (P85)

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    The 'slack' seems like a clutch issue, more than anything else so I was discounting that as an issue for any EV. However, if you can get power to the wheels while just barely holding the car in place with the brakes... that could give a little bit. This would need special override software as well.

    Overall it sounds like completely programming the car ahead of time then having the software do everything but steer it. An interesting technical problem, but if it is solved it kinda takes the fun out of racing EVs. :wink:
     
  10. CapitalistOppressor

    CapitalistOppressor Active Member

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    "Launch" features on high performance vehicles already do many of these things. Every publication publishes the bottom line acceleration numbers using the native launch controls. If the controls do not exist, they have the driver do their best manually. A big reason for Tesla to implement this is so that they are competitive with other manufacturers. And the system I've described is easy to use compared to many systems out there.

    As an example, here is the complaint about BMW M5 launch control published by Car and Driver -

    "TEST NOTES: Launch control is difficult to engage: DSC off, manual shift to “S3” setting, step on brake lightly, hold gear selector forward—but not too long or it drops out—and floor it."

    Hand controls like I've described are common on dragsters, but difficult to implement on regular cars (thinking about it, it might even be illegal for use on city streets. Anyone know?). With a completely electric vehicle that is already computer controlled this should be easy to program.
     
  11. vfx

    vfx Well-Known Member

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    Seems if a "launch control" button simply changes the acceleration curve to be more aggressive rather than the likely compromise to make the car more pleasant that the would be a marked improvement of 0 to "whatever" times.

    There has been comments from Tesla that both the Roadster and Model S are traction limited though I would bet that here is a bit more to be had in both.
     
  12. WarpedOne

    WarpedOne Supreme Premier

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    Thread title is a misnomer - not a "launch feature" but a less aggressive and slip-allowing TC.
    Electric drive train is so precisely and timely controllable that any in-advance knowledge of road conditions isn't necessary. Actually is bad because road condition vary from one minute to another and after every foot traveled. Car constantly monitors for any slip and lowers the torque if it finds any. In principle that is all that is needed. Sport setting could/should/does(?)) only change how quick is this torque-lowering and how strong,

    Oh, and battery could be pre-heated a bit..
     
  13. VolkerP

    VolkerP EU Model S P-37

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    Why not launch with voice command? "Three, two, one, GO!"
     
  14. W8MM

    W8MM R1.5 #325 + Mdl S #01380

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    You wouldn't happen to be a personal injury plaintif's attorney, would you? :rolleyes: :biggrin:
     

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