Why do electric cars have more torque?

Torque VS power reconnaissance

  1. Forums
  2. > Comments
  3. ›Science
  4. ›All comments on the article
  5. ›BMW i3: electric car with ...
  1. theme

New topic Change view


  1. Torque VS power reconnaissance

    Author: gonad 22.07.13 - 19:32

    Unfortunately, terms are jumbled up here when it comes to torque.

    The torque M [Nm] of a motor always relates to a single revolution. Initially, this has little to do with the propulsive force.
    The power P [W] results from P = 2 * pi * M * n, where n stands for the speed.

    Diesel engines, for example, have significantly more torque than gasoline engines but often the same or less power. Why? A diesel engine doesn't turn that high.

    Especially with combustion engines, power and torque are not linear. This is mainly due to the efficiency of the internal combustion engine. At high speed, the friction increases, so the torque and thus the power of the motor decrease. The trick of the auto industry is to specify the maximum torque. But the maximum performance does not have to be there.
    Otherwise there would only be sports cars with diesel :)

    An electric motor behaves differently. It has a significantly higher efficiency of over 90%. This is particularly noticeable in the low speed range. A stationary combustion engine doesn't do anything, it even needs a flywheel to function. An electric motor has the highest torque and therefore the highest output, especially when it is at a standstill, since friction is not relevant here.

    The only advantage of the electric motor is its efficiency, which is almost linear to the speed. It doesn't have to have more torque than an internal combustion engine.

  2. Re: Torque VS Power Enlightenment

    Author: Emulex 22.07.13 - 20:05

    But you mustn't forget to mention that the decisive factor for acceleration is the torque on the wheel and not that of the motor.
    Electric cars usually only have one gear and thus a correspondingly long gear ratio that greatly reduces the wheel torque.
    In addition, the engine torque then drops steadily, which brings nice 0-50 times, but is not so popular later on. Let's say 80-120 to overtake on the country road.
    That is why they are all so slow compared to equally powerful internal combustion engines - the power is simply no longer available for high Vmax due to the concept.
    Of course, this also means that a Tesla that runs 200 will almost fall asleep from 180-200.

  3. Re: Torque VS Power Enlightenment

    Author: gonad 22.07.13 - 20:19

    In principle you are right.
    Gearboxes are often left out of electric motors, but it also works with them.

    However, combustion engines also have torque losses towards the top and they fall asleep in the same way. The trick is just to lock the engine down before you notice it.

  4. Re: Torque VS Power Enlightenment

    Author: Emulex 22.07.13 - 20:25

    Yes, in principle you would also have to regulate the Tesla at 7000rpm:
    http://www.cbcity.de/zur-laengsdynamik-des-tesla-roadster-s

    But it can go up to 14,000 so that you can save the gear.
    I think it's a shame that you don't bring electric cars with transmissions - is there anything technically speaking against it?
    I haven't seen a single one yet.

  5. Re: Torque VS Power Enlightenment

    Author: Oh 23.07.13 - 04:22

    The Tesla Roadster in the first production series had a two-speed transmission, which they dropped in the other models because it caused trouble. The gearbox also robs you of efficiency, it means additional wear parts and additional weight. It is also not true that the Tesla would degrade at high speeds. It is more the case that with the good efficiency of this drive, the air resistance as an efficiency killer is more important than with internal combustion engines. This is why all series-produced electric vehicles are limited to relatively low top speeds. Consumption increases or the range decreases disproportionately at a very high speed. I can think of other electric vehicles with gears: the old Golf Stromer from the eighties, it just kept its gearbox:], and there is an electric motorcycle series from Bramo with classic gears.

  6. Re: Torque VS Power Enlightenment

    Author: Emulex 23.07.13 - 18:30

    Take a look at the PDF that I have linked, there is the performance diagram.
    Pmax at about 6000rpm and then it goes down.
    At 200km / h it still has 100PS - that is also the reason why it only drives 200km / h, because the performance can no longer overcome the air resistance.

  7. Re: Torque VS Power Enlightenment

    Author: josef64 23.07.13 - 20:55

    "The power P [W] results from P = 2 * pi * M * n, where n stands for the speed. ......
    .....
    An electric motor has the highest torque and therefore the highest output, especially when it is at a standstill, since friction is not relevant here. "

    Super nice! (meant cynically)

    You want to teach others, throw around with formulas and obviously understand the wrong thing about it yourself - in view of your verbal explanation, which is absolute nonsense.
    An engine performs according to your "own" - obviously only written formula that you don't seem to understand (x stands for '2 * pi * M'):

    x * n

    at speed n = 0

    0 (, comma josef) watts
    In words: an engine at a standstill does NOT deliver any power!
    ... when "let go" it accelerates from standstill from standstill undoubtedly fastest ... But acceleration is another physical quantity that you have confused with performance without a doubt.
    lg and no offense .... you meant it well: D

  8. Re: Torque VS Power Enlightenment

    Author: Oh 23.07.13 - 21:22

    This is a very compelling PDF, sry I skipped it. On the other hand, there are other descriptions of the drive:

    http://de.wikipedia.org/wiki/Tesla_Roadster:

    > The two-seater sports car is powered by a 215 kW (292 hp) electric motor in the rear. The maximum torque of 370 Nm (400 Nm for the Sport version) [2] is available at speeds of 0–5400 rpm. The originally planned two-speed rear axle transmission was discarded because the prototypes did not meet the requirements for the longevity of the vehicle. Instead, the final series form has a single-speed transmission. All Tesla Roadsters manufactured up to the time of the conversion initially received the two-stage pre-series transmission, which, however, is locked in second gear in order to limit the acting mechanical load forces. As part of the manufacturer's guarantee, this solution was later replaced by the single-speed gearbox for all vehicles delivered in this way.

    > With the final gearbox, the vehicle can reach 100 km / h in around 3.7 seconds; the models delivered earlier still need 5.7 seconds for this. In order to protect the transmission mechanics and to reduce the load on the battery, the roadster is electronically limited in favor of the range at 201 km / h (125 mph).

    It is not so easy for me to understand to what extent the calculations of the author of the article you linked are correct, and a bit of sensationalism also shines through. The values ​​of the roadster look fantastic compared to the TFSI mentioned and are superior in almost every situation, especially in the acceleration situations that are crucial for the racetrack. This is also reflected in the quarter mile on which the Teslas shine. The main problem of the roadsters on the racetrack is not their performance but their rather bad weight distribution due to the 300 kilo battery behind the seats that messes up the vehicle control in the corners. The author ignores this fact and wrongly puts the resulting lean lap times back on the drive. Maybe he didn't know, he also states that he has determined all of this purely theoretically and would like a roadster owner who could confirm his values ​​to him.

    My conclusion: not uninteresting but always nice to read twice.

  9. Re: Torque VS Power Enlightenment

    Author: gadthrawn 18.05.16 - 12:33

    Oh wrote:
    --------------------------------------------------------------------------------

    To warm it up.

    https://teslamotorsclub.com/tmc/attachments/tesla-model-s-power-and-torque-inc-dyno-png.63626/
    http://www.cbcity.de/wp-content/uploads/2012/07/Kennlinie-Leistung-Drehmoment-Tesla-Roadster-S-520x335.png

    - Even without air resistance, the engine's torque drops sharply.

  1. theme

New topic Change view


To comment, please log in or register. You must also go to your account profile under Forum have assigned a username. To the login

  1. University Hospital Frankfurt, Frankfurt am Main
  2. Securiton GmbH alarm and security systems, Achern
  3. DUAL Germany GmbH, Cologne
  4. Konstanz University of Applied Sciences, Constance

Pure golem
  • Use Golem.de without advertising

  1. 4,99€
  2. (including Resident Evil 7 for € 7.99, Project Cars for € 3.30, Hitman 2 for € 14.99, The Sinking ...
  3. 6,99€


Did we miss something?

Email to [email protected]


© 1997-2021 Golem.de. All rights reserved.