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Comment by jessriedel | Hacker News Reader

How much are electric cars limited by raw torque and power? My impression is that a stock Tesla (pricy, but far from "supercar" prices) already has enough torque that it can turn the wheels past the point where they lose traction even up to quite high speeds. (Anyone know what speed?) If so, then the car's performance in that regime is limited not by engine power but presumably by things like the aerodynamics, sophisticated anti-slip electronics, and chassis movement.

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What really limits electric vehicles for racing is weight and batteries. Weight is always bad, and batteries are heavy. And batteries can overheat, which means going into limp mode. The overheating seems to be getting solved relatively quickly, but the weight of batteries isn't going to come down drastically any time soon.

They're just different - electric is better in a lot of ways and gasoline is better in a lot of ways. I don't think you'll see electric cars doing endurance racing anytime soon.

I'm not a racing or really car enthusiast, but, don't races have pit stops where mechanics change out the tires and such? Tesla's old 90-second battery replacement tech could be used here. Just thinking out loud.

90 seconds for a pit stop is an eternity.

Just for those that don't know, pitstops these days are under a few seconds. See for example: https://www.youtube.com/watch?v=OAd_t4wibM0

That's slightly misleading, as that pit stop didn't include refueling. Adding fuel will add about ~10 seconds to the pit stop. But you're still comparing ~10 seconds with ~100 seconds, which is an order of magnitude difference, when many actual races have been lost over 2 second delays in pit stops.

You could do much better with a specialized high-risk vehicle, probably on the order of a couple of seconds.

There's Formula E racing, their solution was to have 2 cars and the drivers switched. An interesting company to look at is Lucid Motors they provide a battery pack that lasts all race now.

tesla never had 90sec battery replacement tech

EVs made explicitly for racing very short distances often have fairly small battery packs and use DC motors instead of AC -- as they have no need for regeneration, the motors are cheaper, the wiring is simpler and the possible torque is insane.

Their chief limitation is managing heat, and maintaining the DC motors themselves.

For example, electric drag racing: https://en.wikipedia.org/wiki/Electric_drag_racing

They would also have to consider how the mass of a battery affects safety as a car goes airborne and hurtles toward other cars, fences and spectators, as well as establish the right protocol for when batteries catch fire, etc.

A stalled car in Formula 1 (last race year?) cause the driver to have to "hop" out of the car with both legs at the same time. This was to prevent a possible ground path from one leg to the other as a result "stepping" out the car.

For raw 0-60 times a big "advantage" of the Teslas are actually their massive curb weight. There's no shortage of gas cars that can also spin their wheels at launch (or even after shifting to 2nd gear). The limiting factor for a launch is mostly friction, and you can get more friction by either increasing the tire's contact patch (such as wider tires) or by adding more weight. Yes that's now more weight you need to accelerate, but assuming you have enough power it's still a net-win.

That weight is terrible for all sorts of other reasons, but that massive ~4,900lb curb weight combined with all-wheel drive is a major factor in the Model S's 2.3 second 0-60 times.

A lot, actually. Tesla batteries are capable of 1500A @ 350V (and much more on a temporary basis, ie Ludicrous mode), which is already 535kW ≈ 717 HP.

Not at high speeds! Or at least, not in a way that's unique to electric motors. ICEs use multiple gears, but it's a similar overall torque picture. (Try multiplying out ICE torque with its gear ratios some time!)

Torque is k*HP/rpm, whether electric or ICE. If you can slip the wheels you can go faster. It's well known in the supercar world that you can often do a great estimate of top speed based on HP alone, given how aero dominates at speeds above 100mph and these cars aren't wildly more drag-efficient than one-another.

At high speed you can increase downforce and thus grip at the cost of increased drag. At lower speeds your limited to the tires which are effectively independent of the rest of the car. At high speeds wind resistance eventually dominates so:

Top speed ^3 * cross sectional area * drag coefficient = HP.

Which is why supercars are so low to the ground, having 1/2 the cross section effectively doubles your horsepower. Though that’s assuming the car can handle the forces involved.

At what speed to you expect the Tesla to be engine-power limited rather than traction limited? (I certainly didn't intend anything like 100mph, but I was thinking like ~40mph.)

I've heard that EV motors need to be guardrailed to keep them from snapping the axles.

The axle strength on this thing must be crazy.

7 electric motors must be able to crank out torque.

look at the youtube videos where tesla updated "track mode" for the model 3.

(people don't generally realize the model 3 performance is almost 500 hp)

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