Why is engine torque an important number?

It seems that torque to the wheels can be increased by changing the gear ratio.

Electric motors have high torque, but the hybrids don't seem to have spectacular acceleration from 0 to 30 mph where one would expect them to excel.

-- Ron

Reply to
Ron Peterson
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Correct. Power is the end result we want to achieve. "Low-end torque" is desirable only when it translates into usable power at low rpms, which has good correspondence for most gasoline engines.

Two points of note:

  1. The quoted electric motor torque may be misleading. Engine torque is typically quoted at the flywheel (i.e. upstream from the transmission), where electric motor torque may be quoted further downstream in the driveline. Audi once quoted 3,319 lb-ft for its E-Tron supercar at the wheel, which seemed enormous until you realize an ubiqitous Camry makes about 2412 lb-ft at the wheel (248 lb-ft at crank x 3.300 first-gear x
3.685 axle ratio - 20% driveline losses)

  1. Depending on the type of electric motor, the quoted torque is the stall torque, i.e. 0 rpm. As the rpms increase, the torque ramps down. In a typical gasoline engine, the torque starts low at 0 rpm, then plateaus at

1500-2000 rpm, then either swells a bit or stays relatively constant.
Reply to
First of One

True.

The torque generated by an electric motor depends on the design of the motor. The advantage of an electric motor is that it generates torque as soon as it starts spinning as opposed to an internal combustion engine, which needs to spin up before useful torque is generated.

Hybrids generally do not have spectacular acceleration because the electronic controllers limit the motor rpm to preserve battery charge. Spectacular acceleration is achievable with an electric motor if battery charge is not the prime concern.

Reply to
Ray O

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