Torque Limiters

Torque limiters are ECU functions that cap engine output based on various conditions. They protect the drivetrain, emissions systems, and engine from damage while ensuring consistent vehicle behavior.

Overview

Multiple torque limiters work simultaneously — gear-dependent, temperature-dependent, smoke-based, and component protection limiters. The lowest limit always wins.

Types of Torque Limiters

• Gear-dependent limiters — lower torque in low gears
• Temperature limiters — coolant, oil, intake air
• Smoke limiters — based on air/fuel ratio
• Component protection — clutch, gearbox, axles
• Altitude limiters — reduced air density

Maps Involved

• Maximum Torque vs Gear
• Temperature Derating Maps
• Altitude Correction Maps
• Drivetrain Torque Limits
• Transient Torque Limits

Logic Sequence

Driver Torque Request
         ↓
Apply Gear Limiter
         ↓
Apply Temperature Limiters
         ↓
Apply Smoke Limiter
         ↓
Apply Component Protection Limits
         ↓
Final Allowed Torque

Calibration Objectives

• Allow maximum safe torque for the build
• Protect upgraded components appropriately
• Maintain drivability in all conditions

Calibration Strategy

• Raise limiters proportionally to actual hardware capability
• Document which limiters are modified for future reference
• Test under heat soak conditions

Diagnostics

• Torque limitation active (may not set DTC)
• Reduced power feeling under specific conditions
• Limp mode from torque monitoring mismatch

Best Practices

• Understand which limiter is active before raising others
• Keep safety margin for real-world conditions

In Calibration Practice

Multiple ceilings stack — per-gear, clutch state, temperature, component protection, market — and the lowest one wins at any moment. Logs that show delivered torque plateauing under the request are displaying whichever limiter is active, and coherent tuning raises the stack together with the hardware’s real capability, never one line in isolation.

Related: on supported vehicles this system is directly addressed by our torque monitoring disable service. See also Thermal Protection in the knowledge base.