How engine protection works
Think of it as a two-part system. Each sensor's diagnostics decide what counts as a fault, such as oil pressure too low, fuel pressure dropping, a temperature getting too high or the mixture going lean. For every one of those faults you choose a severity: none, or Level 1, 2 or 3. The Engine Protection node then decides what each level actually does to the engine.
That split is what makes it useful. You can set a slightly high intake temperature to a gentle Level 1 that pulls a little timing, and low oil pressure to a Level 3 that drops the rev limit hard.
On top of the severity levels, Nexus can also shut down individual cylinders based on a maximum exhaust gas temperature. That feature is covered in our cylinder shutdown article.
What you can set for each level
| Setting | What it does | Our advice |
|---|---|---|
| Enable | Turns that severity level on or off | Enable every level you've assigned a fault to |
| Enrichment | Adds a percentage of fuel as an overall correction. Shown when there's no target lambda table, such as the Injection Time fuel method | Modest enrichment adds a margin without drowning the engine |
| Target Lambda Enrichment | Takes an amount off the lambda/AFR target so the engine runs richer. Shown when a target lambda table exists (VE or MAF fuel methods, or O2 control on) | Same idea as above, expressed as lambda |
| Boost Correction | A percentage change to boost pressure while protection is active. Needs boost control enabled | For serious faults, pull boost well back |
| Retard | Degrees of ignition timing removed | A little on Level 1, more as severity rises |
| Rev Limit Type | Fuel cut or ignition cut | Match the method you use on the main limiter unless you have a reason not to |
| Rev Limit End | The RPM ceiling while protection is active | Low enough that a damaged engine can still be driven off the track gently |
| Active Condition | What has to happen before normal running returns | See below |
The rev limit here doesn't override the others. The ECU always uses whichever limiter is lowest at that moment, whether that's the main limiter, launch control or engine protection.
Clearing protection: Active Condition
- Current and Past DTCs: protection stays on until you clear the code in NSP. Turning the car off and on won't reset it. Use this for faults that mean "stop and look," like low oil pressure.
- Current DTCs only (Drive Cycle): protection stays on until the ECU powers down, then normal running returns on the next start. Good for milder faults where a restart is acceptable.
A setup we often start from
Every engine is different, so treat this as a framework rather than numbers to copy:
- Level 1 for early warnings, such as air temperature or coolant starting to climb. A little retard and some enrichment, reset each drive cycle.
- Level 2 for real problems that aren't instantly fatal, like fuel pressure falling behind. More retard, reduced boost and a lower rev limit.
- Level 3 for faults that can destroy the engine in seconds, like low oil pressure under load. Heavy boost reduction, a low rev limit, and latched until a person clears the code.
Then test it. Trigger each fault safely, with the car stationary, and confirm in your log that the right level activates and does what you expected.
Protection only works if the sensor diagnostics are set up. A severity level with no faults pointing at it never activates. Check each sensor's diagnostics settings, and see our article on oil pressure and engine protection for a worked example.
Troubleshooting
| Symptom | Usually |
|---|---|
| Engine stuck at a low rev limit after a restart | That level is set to Current and Past DTCs; clear the code in NSP |
| Fault logged but nothing changes | That severity level isn't enabled, or the fault has no severity assigned |
| No Enrichment setting shown | Your fuel method uses a target lambda table, so use Target Lambda Enrichment instead |
| Protection triggers on a healthy engine | Sensor limits too tight, or a wiring fault causing false readings |
Related reading: engine protection wiring and engine limiting channel states. Running an Elite instead? See Elite engine protection.
