Comment on Tesla Cybertruck gets less than 80% of advertised range in YouTuber’s test

skysurfer@lemmy.world ⁨5⁩ ⁨months⁩ ago

• TheIllustrativeMan@lemmy.world ⁨5⁩ ⁨months⁩ ago

  Most EVs he’s tested hit or exceed the EPA range on this test. Even bricks like the EV9 exceed their EPA range in similar temps.

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• ABCDE@lemmy.world ⁨5⁩ ⁨months⁩ ago

  Why is the efficiency lower on highways?

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  • skysurfer@lemmy.world ⁨5⁩ ⁨months⁩ ago

    Due to electric drivetrains having minimal fixed losses at low speed unlike internal combustion engines. Aerodynamic losses start becoming the largest factor for EVs at relatively low speeds (25-35 MPH) since other losses at so low. This shows up on tests as higher city efficiency and lower highway.

    For an internal combustion engine you are burning a large amount of energy just to keep the engine running, so the slower the speed, the less distance traveled for the fixed amount of running losses and lower the MPG. It isn’t until higher speeds (55-65 MPH) that aerodynamic losses become the largest factor. This manifests as lower efficiency in the city tests and higher highway.

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    • Nollij@sopuli.xyz ⁨5⁩ ⁨months⁩ ago

      It’s also a factor that acceleration/deceleration in an ICE kills mileage. Highway tests maintain a constant speed. If you ran the same test at 35 mph, they would get much better mileage than at 55 (or 70)

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    • flyingjake@lemmy.one ⁨5⁩ ⁨months⁩ ago

      Idle losses are real but not very substantial in a modern engine compared to the bigger factor you’re missing which is that in city driving tests there is a lot of speeding up and slowing down, ICE vehicles throw away all the energy used to slow down as heat in the brakes which makes city cycles particularly inefficient while an EV captures that energy through regenerative braking, dramatically reducing the net cost of those momentum changes.

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      • snowe@programming.dev ⁨5⁩ ⁨months⁩ ago

        Regenerative braking only can recapture something like 2-5% of lost energy. The bigger factor is exactly what the other person said.

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      • skysurfer@lemmy.world ⁨5⁩ ⁨months⁩ ago

        Ah, good point, the speed changes for ICE ended results in lots of energy wastes due to heat instead of being recaptured. That would certainly be the largest loss for an ICE in the city cycle.

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    • ABCDE@lemmy.world ⁨5⁩ ⁨months⁩ ago

      That makes sense, thanks.

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  • Critical_Insight@feddit.uk ⁨5⁩ ⁨months⁩ ago

    It has the aerodynamics of a brick

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    • TheIllustrativeMan@lemmy.world ⁨5⁩ ⁨months⁩ ago

      So does the EV9, but it exceeded the EPA range in the same test.

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      • Critical_Insight@feddit.uk ⁨5⁩ ⁨months⁩ ago

        This was a highway test though, not how EPA test the ranges

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    • ABCDE@lemmy.world ⁨5⁩ ⁨months⁩ ago

      Aha yes, but what about other EVs?

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  • statue_smudge@lemmy.world ⁨5⁩ ⁨months⁩ ago

    There’s more air resistance at higher speeds.

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    • ABCDE@lemmy.world ⁨5⁩ ⁨months⁩ ago

      That doesn’t explain why ICE vehicles are much better efficiency-wise than EV ones at higher speeds, just why EVs don’t do so well. Another post responding to me addresses it well.

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      • Nollij@sopuli.xyz ⁨5⁩ ⁨months⁩ ago

        Do you mean that ICE is more efficient than EV at higher speeds, or that ICE scales better than EV?

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  • WaterWaiver@aussie.zone ⁨5⁩ ⁨months⁩ ago

    Aerodynamic drag increases with the square of speed. All cars have a different optimum speed for maximum range (which depends on wind speed & temperature too).

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  • eatfudd@lemm.ee ⁨5⁩ ⁨months⁩ ago

    Air drag

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