Changing at max torque is always gonna be slower than riding out the gear.

Firstly, power is what makes a fast car, not torque. Power is torque multiplied by RPM (multiplied by a scaling factor). So even if your making less torque, doing it at a higher RPM will mean more power. And power is what accelerates the car.

And ontop of the above point, even if your making less up in the high RPMs. Holding onto the gear longer is still gonna be quicker for other reasons.
The lower gear ratio will allow the power to accelerate the car faster than a higher gear ratio.

And ontop of those 2 above reasons, there is a 3rd reason. If you can keep a lower gear at the 400m, then it means you not wasting time shifting gears, that is like half a second more time you can spend accelerating instead of coasting.

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Doing it for all the wagons out there