Thermal Protection

Key takeaways

Thermal protection guards coolant, oil and charge-air temperatures via graduated response.
Enrichment, torque reduction and derating escalate as heat rises.
Persistent derating is a cooling-margin problem, not a software one to delete.

Thermal protection functions reduce engine output when critical temperatures exceed safe thresholds. This protects pistons, turbochargers, exhaust manifolds, catalysts, and other heat-sensitive components from damage.

Overview

The ECU monitors multiple temperature inputs and applies torque derating when limits approach. Protection may be gradual (progressive reduction) or immediate (limp mode) depending on severity.

Monitored Temperatures

Coolant temperature
Oil temperature
Intake air temperature
Exhaust gas temperature (EGT)
Turbo inlet/outlet temperature
Catalyst temperature (modeled)

Maps Involved

Temperature Threshold Maps
Torque Derating Maps vs temperature
EGT Protection Maps
Fan Control Maps

Logic Sequence

Temperature Inputs → Compare to Thresholds
         ↓
If approaching limit → Begin torque reduction
         ↓
Activate cooling (fans, enrichment)
         ↓
If critical → Limp mode / warning light
         ↓
Monitor for recovery

Calibration Objectives

Prevent thermal damage to engine/turbo
Allow recovery without shutdown when possible
Provide driver feedback

Calibration Strategy

Raise thresholds only if cooling is upgraded
Monitor actual temperatures during extended WOT
Consider ambient conditions

Diagnostics

Overtemperature DTCs
Frequent thermal derating
Cooling system faults

Best Practices

Thermal protection exists for good reason — respect it
Upgrade cooling before raising thermal limits
Data log temperatures during performance testing

In Calibration Practice

Component protection acts through enrichment on petrol and through torque/boost derates everywhere: exhaust valves, turbine and catalyst each have a temperature budget the file must respect. Sustained-load testing — the autobahn pull, the loaded trailer climb — is where these strategies live; a calibration that only saw a dyno has never met its own protections.

Why does my car reduce power when hot?

A thermal model or sensor crossed its threshold and the ECU is shedding load to cool a component — coolant, oil, charge air or exhaust. That is protection functioning. Recurrent derating means the cooling system’s margin is short, not that the limit is wrong.

Can thermal protections be removed for track use?

They can be rebalanced within engineering margins, but removing them does not remove the heat — it removes the warning before damage. Track builds add cooling capacity so the protections rarely trigger, rather than blinding the ECU to temperature.

Related: on supported vehicles this system is directly addressed by our torque monitoring disable service. See also Component Temperature Protections (ECT, IAT, Oil) in the knowledge base.