Torque-based engine management is the fundamental control philosophy used in all modern ECUs. Instead of directly controlling fuel or ignition, the ECU calculates torque requests and then determines how to achieve them.

Übersicht

In torque-based systems, every input (driver pedal, cruise control, traction control, AC compressor) is converted to a torque request. The ECU then coordinates airpath, fueling, and ignition to deliver exactly that torque while respecting all limits and protection strategies.

Why Torque-Based?

• Unified interface — all systems communicate in the same unit (Nm)
• Predictable behavior — transmission, traction control know what to expect
• Safety integration — torque limits directly control engine output
• Emissions compliance — precise torque control enables consistent emissions

Torque Request Sources

• Driver wish — pedal position interpreted as torque demand
• Cruise control — speed maintenance torque
• Idle controller — minimum torque to maintain idle RPM
• Traction control — torque reduction requests
• Stability control — individual wheel braking + torque reduction
• Übertragung — torque requests during shifts
• AC compressor — load compensation

Torque Coordinator Logic

Driver Wish Torque → Min/Max Limits Check
         ↓
External Requests (TC, ESC, Trans)
         ↓
Minimum Selection → Final Torque Target
         ↓
Split into: Airpath Target + Fuel Target + Ignition Target
         ↓
Actuator Commands

Torque Types

• Indicated torque — theoretical torque from combustion
• Inner torque — indicated minus pumping losses
• Crankshaft torque — inner minus friction losses
• Wheel torque — after drivetrain losses

Torque Paths

The ECU calculates torque through multiple independent paths:

• Air-based path — torque estimated from air mass and efficiency
• Fuel-based path — torque estimated from fuel quantity (diesel)
• Model-based path — torque from physical engine models

These paths are cross-checked by torque monitoring for safety.

Calibration Implications

• Increasing boost/IQ without adjusting torque model triggers safety systems
• Torque limiters override driver requests — must be raised for more power
• Smoke limiter affects achievable torque in diesel applications
• All paths must agree or torque monitoring intervenes

Tuning Sequence

1. Adjust airpath (boost targets)
2. Adjust smoke limiter to allow more fuel
3. Raise torque limiters to allow more output
4. Increase fuel (IQ) to utilize available air
5. Optimize timing (SOI/ignition)
6. Verify torque model consistency

Best Practices

• Never skip the torque model when tuning — it’s not optional
• Keep all torque paths consistent to avoid limp mode
• Understand that “more fuel” alone won’t increase power without torque model changes
• Modern ECUs are smarter than brute-force approaches