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Comment by nategri | Hacker News Reader

True, however I would point out that elevation should have absolutely no impact on the performance of electric vehicles.

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Air density and temperature should both have an influence on the performance of electric vehicles, and both change with elevation.

Maybe on a very hot day cooling would become a factor on the track, but for a single 0-100 run air temperature should be irrelevant. Electric cars don't need to ingest hundreds of grams per second of air to make high power outputs. Unless you're referring to the impact of air density on aerodynamic drag, which should be negligible at such low speeds.

Aerodynamic drag is hugely significant. It dominates at highway speeds. Reduced drag will be very much noticeable on a 0-60 run.

Drag is definitely not neglible at those speeds.

Home runs travel further at Coors Field. Field goals are longer at Mile High. Sprinters turn in faster times at higher altitudes. You can bet that the air density will affect vehicle acceleration tests significantly.

Drag scales with the square of velocity. A 110 mph home run experiences vastly more drag than a car traveling 30 mph on its way to 60 mph. The ball might fly 18% faster in Denver than it will at sea level, but the car isn't going to accelerate 18% faster.

There's a whole raft of other aspects. Temperature will affect traction, for example. Similarly, the pressure differential between the tyres and the atmosphere will change their performance similarly to pressurising tyres to a different pressure at sea level.

There's a whole raft of influences that altitude may have that aren't immediately apparent. To say it has 'absolutely no impact' is simply wrong.

You ignored the sprinter and the football in my list of examples.

> the impact of air density on aerodynamic drag, which should be negligible at such low speeds

The impact air density on aerodynamic drag is huge even in human athletic events - on the order of 1% or more [1]. The impact increases quadratically with speed so it should be 3-5 times more significant in the final stretch of a 0-60 than at the 25mph speed of a sprinter.

[1] http://www.ingentaconnect.com/content/nrc/cjp/2003/00000081/...

I'll add to the other responses that downforce is also something to be considered and air density is a factor there as well.

The person I was responding to said "absolutely no impact", which is absolutely incorrect. I don't have a great intuition of how significant these factors are on the model, but I would not dismiss the terms without careful consideration when we're measuring results in fractions of a second.

Different air density can have a huge impact, given the effects of drag.

It would still affect the air resistance.

If anything it would have more impact since the lack of oxygen at higher altitudes won't effect the engine (as it would in gasoline-powered vehicles), but it'll still change the drag.

Shouldn't higher elevations have a tiny difference in lowering wind resistance from thinner air? It's definitely a much smaller effect than on a IC engine.

With lower air density the electric car could be slightly faster at elevation.

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