An exhaust gas recirculation valve feeds a controlled amount of exhaust back into the intake. The exhaust has already burned, so it carries very little oxygen. Mixed into the fresh charge, it takes up space and slows the burn, which lowers peak combustion temperature. Lower peak temperature means less nitrogen oxide (NOx) is formed. That's the main reason factory engines have EGR, and part-load efficiency can improve as well.
The Nexus Recirc Valve function drives that valve from an ECU output. The main page has one core setting:
| Setting | What it does | Our advice |
|---|---|---|
| Output Frequency | The fixed frequency the valve output is pulsed at | Match what the valve maker specifies. The wrong frequency can make a valve buzz, stick or respond poorly |
How far the valve opens is set in the Recirc Valve Output Table, and the physical output is assigned in Recirc Valve Wiring.
Keep EGR to light-load cruise conditions. Recirculated exhaust at high load takes the place of fresh air the engine needs for power. Tune fuel and ignition with EGR both active and inactive, and confirm the valve's behavior in logs.
If your build has removed the EGR system, you can leave this function disabled. Check your local emissions rules before deleting anything on a street car.
