It shows Power and Torque vs RPM curves that are typical of traditional reciproc

Question

It shows Power and Torque vs RPM curves that are typical of traditional reciprocating engines Here are data points for a couple of well known sports cars: 2016 Corvette C7 Z06 max power = 650 hp @ 6400 RPM; max torque = 650 ft-lb @ 3600 RPM 2016 Viper ACR max power = 645 hp @ 6200 RPM. max torque = 600 ft-lb @ 5000 RPM Notice that the RPM for the maximum power always exceeds the RPM for the maximum torque Use the formula P = omega T relating power (P), angular velocity (omega), and torque (T) to show why this must be so, given the shapes of the curves shown above. Put your answer in the space below on this page.

Explanation / Answer

The Torque is dependent on the breathng efficiency(volumetric efficiency) of the engine and as the speed increases breathing efficiency increases initially, reaches maximum at a particular speed and then starts decreasing. This happens because the higher piston speed creates more suction which makes the engine intake more and more air with each stroke but after a particular speed due to flow losses at inlet valve breathing efficiency starts decreasing and hence the decrease in torque.

Power = Torque x speed

But the power still increases even if there is decrease in torque, this is because power depends on torque as well as speed and since the speed is increasing it makes the net effect of increase in power. But after some increase power reaches optimum value and starts decreasing as decrease in torque dominates the increase in speed.

Due to this RPM for maximum power always exceeds the RPM for maximum torque.

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