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0 pointsgucci-on-fleek1mo ago0 comments

> Most notably, air is about 28% denser at -40°C than at 25°C, so drag is about 28% higher. So you would expect roughly 28% less range at high speeds even if the battery has no capacity loss whatsoever.

With my gas car, I haven't noticed 30% worse fuel consumption at –30°C compared to +30°C [0]. To be fair, I haven't closely measured the fuel consumption at different temperatures, but I probably would have noticed such a big difference. This is just anecdotal of course, so your values may actually be correct.

[0]: It does occasionally get down to –40°C here, but my car won't usually start then, so I've slightly shifted your temperature range to the values where I've driven most.

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rootusrootus1mo ago

It won't be as noticeable on a gas car because it is probably starting out around 30% efficiency (as compared with ~90% for an EV). This is a major advantage of gasoline, in a sense, because it means we have already engineered the package to account for a lot of wasted fuel.

gucci-on-fleekOP1mo ago

Ah, so then the air temperature should reduce fuel consumption by 30%×30%=10%, which does seem to roughly match my experience. Thanks for pointing that out!

simulator5g1mo ago

Internal combustion engines are actually more efficient in cold weather than hot weather. But the other factors like drag outweigh the increased efficiency of the engine. And since gas engines are so inefficient to begin with you don't notice much of a difference. https://physics.stackexchange.com/questions/270072/heated-an...

layla5alive1mo ago

Gas cars produce more power at lower temperatures - more oxygen gets into the combustion chamber, and the engine also can run more advanced spark timing without as much worry of detonation. This is why turbochargers have intercoolers.

Aspos1mo ago

Air drag energy losses are tiny comparing to other losses when burning petrol so you don't notice the difference.

gucci-on-fleekOP1mo ago

Ohhhh, that makes complete sense, thanks!

schiffern1mo ago

  >your values may actually be correct

They used PV=nRT, so it better be!

Note that a 28% increase in drag results in a roughly 22% decrease in range, because 1/1.28 ~= 0.78. Also there are other losses (like rolling friction and constant loads like headlights or cabin heat), so range doesn't scale perfectly with drag. Drag is the main source of loss at highway speed, however

randomname938571mo ago

I drive long distance weekly on my gas car. Full tank in summer (+20C) gives me 520 km, while in winter (-20C here) I get 430-440 km. I noticed it on my current and previous cars. Maybe it's thicker oil and worse car efficiencies in winter ? And that's despite that full tank of gas has more gas in winter comparing to summer, gasoline is denser in cold temps.

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0 pointsgucci-on-fleek1mo ago0 comments

[0]: It does occasionally get down to –40°C here, but my car won't usually start then, so I've slightly shifted your temperature range to the values where I've driven most.

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rootusrootus1mo ago

gucci-on-fleekOP1mo ago

Ah, so then the air temperature should reduce fuel consumption by 30%×30%=10%, which does seem to roughly match my experience. Thanks for pointing that out!

simulator5g1mo ago

layla5alive1mo ago

Aspos1mo ago

Air drag energy losses are tiny comparing to other losses when burning petrol so you don't notice the difference.

gucci-on-fleekOP1mo ago

Ohhhh, that makes complete sense, thanks!

schiffern1mo ago

  >your values may actually be correct

They used PV=nRT, so it better be!

randomname938571mo ago

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