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Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

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Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#61

Earlier quoted context omitted.

It's not equal torque at all rpm.

Effectively it's more equal then an ICE. Also if you can get someone who has a lot of experience with motor control they can get you going pretty quickly. I'm assuming what's in the Tesla is a brush-less DC motor and there are a few things you can do (especially since you're on some serious batteries in the Tesla) to push some serious torque at the startup curve. You're probably only running a modulated power start f…

As pointed out in other comments Tesla actually uses AC induction machines (asynchronous AC) instead of brushless machines (synchronous AC). To a first approximation an AC induction machine can produce constant torque up to a fixed speed. Above this speed the torque falls off as approximately 1/speed.

You are right about the startup torque. AC induction machines can produce full breakdown torque at zero speed, but this does require high current (but luckily not high power because the applied voltage is still low due to low motor speed).

Another limit is the junction temperature of the power semiconductors in the inverter(s). I think Tesla uses liquid cooled inverters, but this typically means there isn't much mass to act as a heatsink (relying on the liquid coolant instead), so overload times are typically very short. I'd would guess this is actually the limit in their design. In other words they can put very high currents into the motor for a long period of time before it thermally overheats, but way before that time they have to reduce the current in order to protect the power semiconductors in the inverter.

Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#62

Does anyone have an idea of what they did/could have done in terms of software to allow a performance improvement?

I have a guess: the limit in these designs isn't typically the motor, but instead the power semiconductors in the inverter (the motor has a much longer thermal time constant than the power devices). Therefore the limit is the junction temperature of the power devices. Most high performance drives have some kind of junction temperature estimation algorithm (it is difficult or impossible to put a sensor right at the junction without changing the electrical properties of the semiconductor). When the estimated temperature gets too high, they will start pulling back the current to protect the power devices from overheating. The more accurate the model, the closer they can push the devices to the limit without failure.

I'd bet they have been slowly improving their junction temp. estimation model and are now able to push the power semiconductors a little bit closer to their temperature limit, allowing them to produce more current (or the same current for a longer duration) before pulling back.

Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#63
I've imagined Elon, still connected to childhood sci-fi dystopian futures, would most certainly include some secret "God Mode" backdoor that only he knows...

So, in a future where Tesla's are all over the roadways,and the earth falls under alien attack or some other crisis -- he could easily escape by speaking to any nearby Tesla, which would give him full access (maybe even unlocking faster speeds ;). Perhaps even having some sort of transponder to send the nearest Tesla's to his rescue, should that be required.

Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#64
post #6

Earlier quoted context omitted.

At 2.6-sh second mark your car accelerates with more than 9.8m/s^2 to get to 60. But even lower accelerations will glue you to the seat because gravity acceleration affects every part of your body. Where as the car grabs you by the butt and yanks you forward. So - I think he has probably some vague idea of Newtonian physics but just didn't manage to produce coherent sentence.

How is more than one g accelleration possible? There is one g making the friction between the tyre and the road.

I don't understand the question. The car is accelerating horizontally, the gravity acts vertically.

Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#66

Earlier quoted context omitted.

> High school friction is wrong. No, it's at least mostly correct. High school friction says F = mu * W Where F is the output force, mu is the coefficient of friction, and W is the normal force (typically equal to the weight). If it's failed you, it's failed in failing to mention that the tire-road interface can have a coefficient of friction greater than one, and in failing to mention that the normal force can be in…

High school physics tends to claim that the coefficient can't be greater than one. Source: note all the people here who thought it couldn't be greater than one.

How is that due to high school physics rather than naive intuition?

Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#67
post #63

I've imagined Elon, still connected to childhood sci-fi dystopian futures, would most certainly include some secret "God Mode" backdoor that only he knows... So, in a future where Tesla's are all over the roadways,and the earth falls under alien attack or some other crisis -- he could easily escape by speaking to any nearby Tesla, which would give him full access (maybe even unlocking faster speeds ;). Perhaps even h…

In the future where aliens land on Earth and start a ground assault[0], Elon can take all the Teslas left by fleeing civilians and use them as remotely controlled (soon to be autonomous) weapons to fight the invasion, all from the safety of his volcano lair. ;).

--

[0] - Why ground assault instead of orbital bombardment? Well, there aren't many alien vessels left in orbit after a massive onslaught of Falcon 9s and BFRs ;).

Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#68

It also depends on how you define "Worlds fastest car" While there is no doubt this is a fast car and that time is a stonking 0-60 time. I am lead to believe it can't complete a full flat out lap of the Nurburgring as constant high speed/full throttle use heats up the battery to the point where performance has to be limited. So while it will be great to "hoon about" in and should be a win at the traffic light gran pr…

> It also depends on how you define "Worlds fastest car" ... and here they defined it so the P100D is the fastest. Welcome to the tautology club. Meanwhile, Wikipedia has three cars above the P100D on its quickest 0-60 list: the Porsche 918, the LaFerrari, and the Bugatti Veyron. https://en.wikipedia.org/wiki/List_of_fastest_production_car... Note also that Tesla has also been called a bit "optimistic" with their 0-6…

Wikipedia still shows the old 0-60 time for the P100D. At 2.4 seconds, it will be ahead of the Veyron, even with the LaFerrari, and behind the 918.

And Tesla only compares with cars currently in production. The LaFerrari and 918 are not.

Definitely some definitional tweaking to get the "right answer," but not quite a tautology.

Re: Tesla ‘Easter Egg’ Makes the Fast-Accelerating Model S Even Faster

#70

It also depends on how you define "Worlds fastest car" While there is no doubt this is a fast car and that time is a stonking 0-60 time. I am lead to believe it can't complete a full flat out lap of the Nurburgring as constant high speed/full throttle use heats up the battery to the point where performance has to be limited. So while it will be great to "hoon about" in and should be a win at the traffic light gran pr…

The fact is anything below 5 seconds 0-60 is a damned speedy car that you really won't get to push in day to day driving... As it is, I've been in a few Model S's and they are fun. I'll keep my Scat Pack Challenger though, far less expensive, only a second lower, and a higher top speed. Not to mention looking quite a bit cooler imho.
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