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Comment by robryk | Hacker News Reader

In snowy conditions you don't actually want all the torque available: then you'd want to control the torque applied instead of the power delivered when starting to move (similar to placing a restriction on the top torque by shifting into second gear on manual shift cars).

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At least in a Tesla it will automatically dial torque down when slip is detected. It accomplishes this via lowering amperage to the motor, it also can adjust wheel spin using individual wheel braking.

All of this is already working fine with no transmission... Adding one to a consumer EV for snowy conditions is a step backwards in terms of more stuff to break and maintain.

I believe this makes more sense for heavy equipment and freight trucks. You wouldn't want to have the gear ratio for heavy load all the time, as it would require the motor to spin at high RPMs (inefficient) to maintain highway speeds even when the amount of torque required is low.

From driving quite a bit on ice tracks here in Norway, tesla is by far the best there is when it comes to safety on snow/ice.

Not the most fun though unless you enable track mode or disconnect the traction control sensors.

That's why I stick with a manual transmission -- far better handling in snow. Have not asked my EV peers how it's working for them.

As a former driver of many Audi quattros and a Canadian who lives on top of a hill with a AWD Tesla 3 I can say it's the best handling car in snow that I've driven (given clearance limits of a sedan).

The instant reaction speed of its electric traction control to slippage will vastly outperform any manual transmission. You can drive like an idiot with the pedal to the floor and the car sorts itself out.

The real problem with electric cars and modern cars in general in the snow is the sheer weight of the vehicles makes it harder to stop in an emergency.

Most of the crummy AWD systems they throw in the majority of cars these days can get you unstuck or up a hill so that’s not a major advantage.

Also, car makers tend to throw on low friction tires on electric cars to increase range which invites another set of problems.

With proper winter or all-weather tires you'll actually get better stopping for a heavier vehicle (the tires will have more friction as a function of the weight so less chance of slip even though you have more to stop).

I haven't encountered snow since my last manual died but that's my understanding of electronic traction control--give the job to the computer that can do a far better job than any human.

When the computer can outperform a human let the computer do it! Only give control of things where at least some drivers can outperform the computer. And, while not relevant to driving, if there's a grey area let the operator hit an override to use it. (Boeing--the plane does what you tell it even if you go outside the envelope. Airbus--the plane stays in the envelope no matter what you tell it to do. The first makes for broken birds, the second means the pilot in trouble can't decide to risk breaking the bird if that's what's needed. If you need 4g to clear terrain you do it even if the bird is only rated for 3g.)

If the human is doing the traction control job, they know how far from the edge of the envelope they are (because the difficulty changes). If it's a computer doing that, it's hard to communicate that to the human (iiuc we don't even try). Unless this is improved, this means that sometimes it's better to leave a human in control of both strategy and tactics even if the computer would outperform on tactics.

Interesting. I have fanatical Tesla fanboy friends in Denver Colorado who don't drive their teslas much in winter because they handle poorly in the snow on steep inclines and declines. The door lock issues and cold weather battery energy life and charging issues were their other problems

The RWD is a bit of a different beast than the AWD. It's much easier to get stuck on that one due to its weight when reversing up a hill.

ah that explains it, thanks!

Do you have snow tires? Living in a snowy region, I've learned that nothing makes as big a difference as snow tires -- whether the car has stick, automatic, AWD, whatever.

Admittedly, it's hard for me to directly compare stick and automatic because the cars with automatic were also much heavier -- a minivan and a SUV.

North Europe, snow tires are mandatory. That's that - so effectively changing tires twice a year Apr/May and Nov

I'm curious on the relative performance of traction control?

Isn't the goal of traction control to limit the power to the wheel?

Reading on how TCS works [1], it seems it applies the brake and may limit power from the engine?

[1] https://www.scienceabc.com/innovation/what-is-a-traction-con...

Traction control has all sorts of tricks it can use to get you pointed in the right direction. Traction control systems can brake individual wheels to apply rotational torque to counter excessive yaw like when the back tires come loose and the back swings out, the car can induce rotation in the opposite direction to sort things out before they get too dangerous.

The other common case is when taking off in a straight line, the car can limit power in excess of what the wheels are capable of putting down. This is usually accomplished with a combination of limiting power and in some cases braking individual wheels as they lose traction to simulate the effects of having a differential.

Electric cars do better much in the latter case because of how quickly they can limit power compared to an engine. It’s one of the reasons electric cars dominate 0-60 tests because they can adjust power hundreds of times a second whereas that’s simply not possible with a gas engine.

The argument was that the addition of a transmission would allow more control in snow. Is that only in situations where there isn't traction control, or where it is disabled?

Would traction control be expected to outperform a human on snow? Is the higher weight of an EV going to make it handle poorly anyways?

A transmission will do nothing for an EV in the snow. The existing traction management is more than sufficient for starting up but slowing down or changing directions in an EV in traction limited situations will likely always be worse than an equivalent gas car just because of excessive weight.

Traction control will outperform an above average driver on snow. I've driven lots of fast cars sideways and lived in the Northeast my whole life and I leave the TC system on because while I know how to control a slide on a racetrack, I don't want to do the same on a public road.

Agreed, and I’d go so far to say you don’t want all the torque on anything but a clean racetrack. Rain, oil, gravel, animal carcasses… there’s plenty of road conditions where a lead foot plus extreme torque will carry you violently off the road.

And it might be a good trade-off to pair a motor with a peaky torque curve with a 2-speed or 3-speed gearbox.

But if your _only_ goal is to limit torque, you could simulate that by re-mapping the pedal.

Say, by hitting "Eco" mode on a Prius.

My comment is more about why torque should be limitable, not a critique on electric cars.

Most cars have traction control AFAIK. Instead of limiting max torque, they notice when it's spinning the wheels.

Same in reverse for breaks and abs.

On my car you can turn it off if you want some fun on dirt tracks.

Once the wheels are spinning, its often too late. At least in my experience. Its best used to accelerate with minimal spin, and is mediocre - at best - at preventing traction loss in turns of any kind.

Limiting torque is as simple as running the motor in current-control mode

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