What the recirculation valve does
An exhaust gas recirculation (EGR) valve feeds a controlled amount of exhaust back into the intake. That exhaust has already burned, so it takes up space in the cylinder without adding oxygen. The result is a cooler burn, which cuts the formation of nitrogen oxides (NOx) and helps some engines run more efficiently at light load. It's mainly an emissions device, and it's usually closed at high load where you want every bit of fresh air.
In ESP this function is called the Recirculation Valve. The setup has two parts: the output wiring and a duty cycle table.
Wiring tab
| Setting | What it does | Our advice |
|---|---|---|
| Recirculation Valve Output | The output that drives the valve | Usually a spare DPO (digital pulsed output) or a stepper output, to suit the valve type |
| Active State | Whether the output is normal or inverted | Low (default) grounds the output when it's on. High flips that, grounding it when it's off. Leave it on Low unless the valve works backwards |
Recirculation Valve tab
Output Frequency is the fixed rate the output is pulsed at. Match it to what the valve is designed for. The wrong frequency can make a valve buzz, respond poorly or run hot. If you don't know the right value for your valve, check the manufacturer's data or ask us before guessing.
The duty cycle table
The Recirculation Valve Output Duty Cycle table sets how far the valve is driven. You can map it over the channels that suit your engine, such as RPM and load. A typical plan is:
- Closed at idle, where extra exhaust can make the engine rough.
- Some opening at light load cruise, where emissions and efficiency benefit.
- Closed at high load and full throttle.
Make changes in small steps and watch idle quality and lambda, since recirculated exhaust changes how the engine burns. If the engine surges or misfires at cruise, reduce the duty in that area.
Should you keep it?
That depends on your local emissions rules and how the car is used. On a street car that must pass inspection, keeping the factory EGR working is often the easier path. Related Elite functions worth reviewing at the same time are idle control and decel. Not sure how to handle it on your build? Book a free consultation.
