Road and Track test drives the Roadster

[GSP]

As long as your foot is on the brake there is no current going through the motor, but when you remove it full power is immediately demanded and delivered.

WarpedOne,

Are you sure the Roadster does this? If so, there may be an opportunity for Tesla to improve 0-60 times by eliminating this logic. Applying torque to the drivetrain before launch "winds up" the drive shafts (and other parts, including the tires) and compresses the suspension. This stores energy that helps launch the car quicker.

Also, using both feet when cornering to apply torque before releasing the brakes can improve smoothness and lap times when autocrossing or road racing. Does the Roadster also interrupt motor torque when the brake is applied at speed?

GSP

 

[WarpedOne]

This stores energy that helps launch the car quicker.

In Tesla such a process would very very very quickly overheat the motor and PEM if not cause a malfunction - stalled electric motor is practicaly a shortcircuit.

You are generalizing ICE specifics to electric drivetrain. Remember: no sliping clutch, no shifting, no optimal revs, no turbo lag, no gearbox slack, no heating up the engine etc. You touch the accelerator and you get immediate response at max capabilities.

What logic is there at simultaneously trying to stop (applaying brakes) and to accelerate (motor pushing) anyway? None whatsoever. This only tries to cimcurvent the shortcommings of ICE drivetrain wich are amost completely eliminated in electric drivetrain.

There are some miliseconds lost into compresing the susspension, but they are not worth burning the electronics.

 

[GSP]

"What logic is there at simultaneously trying to stop (applaying brakes) and to accelerate (motor pushing) anyway?"

Wining races of course, or getting better performance times to help sell automobiles! :wink:

Take a look at Erik Carlsson's driving career with SAAB for example:

Erik L. Carlsson Biography

If you think Erik's technique only helps FWD cars, there are people who will disagree:

good thinking | Want to go fast? Learn left-foot braking

Michael Schumaker grew up with left foot braking in Karts, and used it in F1 to consistently beat his teammate Rubens Barrichello. Rubens didn't left foot brake, although otherwise he was an excellent driver (and a great guy as well).

In Drag Racing the "launch" is critical, and races are won and lost by milliseconds. If Tesla can save 100 msec by preloaing the rear suspension, they can get a 3.9 sec 0-60 time published in Road & Track instead of a 4.0 sec time.

There is more to it than the suspension, the Tesla's gearbox and half shafts must have backlash in the gears and splines. Preloading the driveline takes up this slack prior to launch. Also, the halfshafts, tires, and other components are actually "springs" of a sort. They deform (stretch) with load (see Hooke's Law). Preloading these components saves time and also stores energy that can by released during the launch.

I thought providing full torque at zero rpm was and electric motor advantage! Perhaps Tesla could provide at least partial torque for at least a few seconds?

Also, I'm curious, does the Roadster really cut torque to zero when the brakes are applied? R & T usually experiments to find the best launch technique for each car. Why would they slowly apply the accelerator to WOT and then release the brakes? If no torque was produced prior to the brake release they likely would have commented (complained) about it.

GSP

 

[elirentz]

I can understand Tesla cutting out "power braking" (What its called holding the brake and gas at a standstill) to save the motor from being overheated. As has been said before on an electric drivetrain powerbraking does very little as there is no torque converter and fewer drivetrain components to wind up. Powerbraking works in an ICE because it preloads the torque converter and allows the car to build some pressure in the case of forced induction

Cutting out left foot braking on a aportscar though would be very strange. For one the stress on the motor would be less because essentially you are just adding more load to the motor and not preventing it from spinning with brakes despite giving it power like with power braking.

 

[WarpedOne]

You guys understand very little.

Powerbraking is there because ICE engines are usless under low revs. Turbocharged engines need high boost levels to really perform. If you lift your foot off gas pedal and brake, revs will fall, boost pressure will be gone resulting in poor acceleration when you press the pedal again. Thats way masters don't ever really lift foot from the gas pedal. They hold the engine in high revs to keep high preassure leveles in turbo/supercharger and/or improve the responsivnes of the engine. Slack in gearbox/drivetrain is minimal (a few degrees at most) and doesn't matter.

There is no turbocharger or supercharger in Tesla Roadster.
You are always in right gear and at optimum revs. The engine is always ultra responsive (much much more then any existing ICE powered car).

Powerbraking in Tesla Roadster is useless waste of energy and dangerous wear and tear on electronics. Powerbraking goes along the need for V8 sound ...

 

[TEG]