3 ms·

Teslas are designed to perform better (and EPA is designed to evaluate) NOT on freeways (ie, where most people drive)(mainly due to very good regenerative braki

by pbreit 6y ago

Teslas are designed to perform better (and EPA is designed to evaluate) NOT on freeways (ie, where most people drive)(mainly due to very good regenerative braking).

taneq 6y ago
All cars perform better (in terms of kWh through the driveshaft per km) at lower speed, since air resistance rises quickly with speed. Tesla can't do anything to change this, although they do try to mitigate it with good aero. Electric cars can regen brake and so recover some energy in stop/go traffic, but they're still more efficient at constant low speed than stop/go at low speed. ICE vehicles only get better economy on the highway because they have no regen braking and their engines are more fuel efficient at highway speeds.
- thdrdt 6y ago
  This is not complete true. Most combustion cars perform best around 90km/h. Below that speed air resistance is not much of an issue but gears help a lot getting the best performance out of the engine.
  - taneq 6y ago
    Yeah, that's what I meant by "their engines are more fuel efficient at highway speeds" - fuel burn is minimized under highway conditions (90km/h as you say sounds about right) since air resistance isn't crazy yet but you're in top gear and so getting the maximum distance per engine swept volume.
    - Theodores 6y ago
      90 km/h or 56 mph was the speed that ICE car fuel efficiency was measured at during the 1970's onwards until recent times. If you read a car review then the mpg figure would be for 56 mph in the UK. For this reason the target speed for efficiency had to be 56 mph. For that would be important for comparisons. Fleet buyers were important in those days so a 'rep-mobile' able to sip the fuel as it went about crossing the country at sensible A road and motorway speeds was what was wanted. If a manufacturer wanted to sell into this market then the 56 mpg figure had to be available. I am not sure fuel efficiency was discussed in quite the same way in the U.S. market during these times and there weren't the same tax incentives to get companies buying 'rep-mobiles' so the auto-sector could be stimulated. Europe wasn't the EU in those days with each major country having different tax regimes for cars.
- pbreit 6y ago
  Is that restating what I wrote?

by pbreit 6y ago

Teslas are designed to perform better (and EPA is designed to evaluate) NOT on freeways (ie, where most people drive)(mainly due to very good regenerative braking).

taneq 6y ago

All cars perform better (in terms of kWh through the driveshaft per km) at lower speed, since air resistance rises quickly with speed. Tesla can't do anything to change this, although they do try to mitigate it with good aero. Electric cars can regen brake and so recover some energy in stop/go traffic, but they're still more efficient at constant low speed than stop/go at low speed. ICE vehicles only get better economy on the highway because they have no regen braking and their engines are more fuel efficient at highway speeds.

thdrdt 6y ago
This is not complete true. Most combustion cars perform best around 90km/h. Below that speed air resistance is not much of an issue but gears help a lot getting the best performance out of the engine.
- taneq 6y ago
  Yeah, that's what I meant by "their engines are more fuel efficient at highway speeds" - fuel burn is minimized under highway conditions (90km/h as you say sounds about right) since air resistance isn't crazy yet but you're in top gear and so getting the maximum distance per engine swept volume.
  - Theodores 6y ago
    90 km/h or 56 mph was the speed that ICE car fuel efficiency was measured at during the 1970's onwards until recent times. If you read a car review then the mpg figure would be for 56 mph in the UK. For this reason the target speed for efficiency had to be 56 mph. For that would be important for comparisons. Fleet buyers were important in those days so a 'rep-mobile' able to sip the fuel as it went about crossing the country at sensible A road and motorway speeds was what was wanted. If a manufacturer wanted to sell into this market then the 56 mpg figure had to be available. I am not sure fuel efficiency was discussed in quite the same way in the U.S. market during these times and there weren't the same tax incentives to get companies buying 'rep-mobiles' so the auto-sector could be stimulated. Europe wasn't the EU in those days with each major country having different tax regimes for cars.
pbreit 6y ago
Is that restating what I wrote?