Torque Limiters

dyno test honda xadv

What is torque? What is torque limiter? How is torque calculated?

Definition of Torque Limiter

dyno test honda xadv

A Torque Limiter, also known as a Torque Management System, is a feature found in modern vehicles, especially those equipped with advanced electronic control systems. It’s designed to limit the amount of torque that the engine can deliver to the drivetrain under certain conditions to protect components from damage, improve drivability, and enhance vehicle stability.

Here’s how a torque limiter typically works:

  1. Electronic Control: The Torque Limiter is controlled by the vehicle’s Engine Control Unit (ECU) or Powertrain Control Module (PCM), which continuously monitors various parameters such as engine speed, throttle position, wheel speed, and vehicle load.
  2. Threshold Detection: The ECU sets thresholds for torque limits based on the vehicle’s operating conditions and performance requirements. For example, during aggressive acceleration, the ECU may allow higher torque output, while during low-traction conditions or when towing heavy loads, it may impose lower torque limits to prevent wheel slippage or drivetrain damage.
  3. Torque Reduction: When the ECU detects that the engine is producing more torque than is safe or necessary for the current driving conditions, it activates the torque limiter. This can involve temporarily reducing engine power by adjusting fuel delivery, ignition timing, or throttle position.
  4. Traction Control: In vehicles equipped with traction control systems, the torque limiter may work in conjunction with these systems to prevent wheel spin and maintain traction during acceleration. By limiting torque to individual wheels or axles, the vehicle can better manage slippery or uneven road surfaces.
  5. Transmission Control: The torque limiter may also interact with the transmission control system to modulate gear shifts and torque converter lock-up to optimize drivability and efficiency while staying within safe torque limits.
  6. Stability Control: In some cases, the torque limiter may be integrated with the vehicle’s stability control system to enhance vehicle stability during cornering, braking, or emergency maneuvers. By limiting excessive torque, the system can help prevent oversteer or understeer and improve overall handling.
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How is torque calculated?

Torque, in the context of automotive engineering, is a measure of the rotational force applied to an object, such as an engine crankshaft or a vehicle’s wheels. It’s calculated using the following formula:


In this formula:

  • Torque is measured in units such as Newton-meters (Nm) or pound-feet (lb-ft).
  • Force is the perpendicular force applied to a lever arm or radius. In the case of an engine, it’s the force generated by the combustion of fuel in the cylinders, transmitted through the pistons to the crankshaft.
  • Distance is the lever arm or radius at which the force is applied. In the context of an engine, it’s the distance from the center of the crankshaft to the point where the force is applied, typically measured in meters or feet.

In simpler terms, torque is the product of the force applied and the distance from the point of application to the axis of rotation. In an engine, torque is commonly measured at the crankshaft, and it represents the engine’s ability to produce rotational force to move the vehicle.

For example, if you apply a force of 100 Newtons at a distance of 0.5 meters from the axis of rotation, the torque produced would be:

Torque=100 N×0.5 m=50 Nm

This calculation illustrates how torque is dependent not only on the magnitude of the force but also on the distance from the axis of rotation where the force is applied.

Torque VS Power


Torque and power are both crucial concepts in understanding the performance characteristics of an engine, but they represent different aspects of its operation.


  • Torque is a measure of the rotational force produced by the engine.
  • It represents the engine’s ability to generate twisting force to rotate the crankshaft.
  • Torque is typically measured in units such as Newton-meters (Nm) or pound-feet (lb-ft).
  • In the context of an engine, torque determines the vehicle’s acceleration and towing capability.
  • Higher torque values generally result in stronger acceleration and better towing capacity.
  • Torque is directly related to the force generated by the engine’s combustion process and the length of the engine’s crankshaft arm.


  • Power is the rate at which work is done or energy is transferred over time.
  • In the context of an engine, power represents the engine’s ability to produce work or deliver energy to move the vehicle.
  • Power is typically measured in units such as horsepower (hp) or kilowatts (kW).
  • Power is a function of both torque and engine speed (RPM), calculated as: Power (P)=Torque×Engine Speed (RPM)
  • Power determines the vehicle’s top speed and overall performance.
  • Higher power values generally result in faster acceleration and higher top speeds.

In summary, while torque represents the engine’s twisting force, power represents how quickly that force can be applied over time. Both torque and power are important in understanding and evaluating an engine’s performance characteristics, but they provide different insights into how an engine performs in different driving scenarios.

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