A conventional petrol engine is normally most efficient at 2000~2500rpm, cruising constantly in top gear at moderate highway speed (50~60km) and without stop start traffic.
My pure guess work here :
For electric motor, the efficiency level of the electric motor is probably linear across the entire revs range, with max torque available at the zero revs, and torque disminish at higher revs as the internal electricial resistance of electric motor increase.
In city driving, the deceleration can actually generate electricty through KERS, where a conventional vehicle will waste such energy as brake heat.
In highway driving, with the vehicle up to speed, wind resistance will increase significantly (in fact by a factor of square vs speed), hence the overall efficiency decrease. In city driving, at slow speed wind resistance is almost nil. |
