ICE-07 — Torque & Power

ASSUMPTION — The curves here are qualitative examples; a real engine’s curve depends on volumetric efficiency, boost and calibration.

In this lesson you will learn:

• The difference between torque and power
• The power = torque × angular speed relationship
• How curves vary with RPM

1. Torque

Torque is the rotational moment at the crankshaft (Nm) — the quantity that determines pulling force (“grunt”).

FACT — Torque is the average moment applied to the crankshaft by gas pressure on the piston. Brake Mean Effective Pressure (BMEP) × displacement is a core indicator of torque capacity.

2. Power

Power is work per unit time (kW or HP):

FACT — Power = Torque × Angular Speed. The same torque at higher RPM produces more power, which is why the power curve rises with RPM while torque plateaus at mid RPM.

3. Reading the Curves

• A flat (plateau) torque curve feels “flexible”.
• The power curve rises with RPM, peaking at high RPM.

EXAMPLE — A turbo engine with flat torque from 2000–4500 rpm accelerates comfortably without frequent gear changes.

4. Why Both Matter

• Torque → pull, launch, hill climbing feel.
• Power → top speed and peak performance.

INTERPRETATION — High power does not always mean a “nice” engine; drive feel is tied to the torque curve shape (low-end torque). It is always an application-dependent trade-off.

5. Summary

• Torque (Nm) is rotational moment; power (kW/HP) is work per time.
• Power = torque × angular speed.
• Torque plateaus, power rises with RPM.
• Torque defines pull; power defines peak performance.

6. Sources

• Heywood, Internal Combustion Engine Fundamentals
• Bosch Automotive Handbook

Next Lesson

• ICE-08 — Volumetric Efficiency: how well the cylinder fills with air.