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AFR CLOSED LOOP

The system can sense the lambda in the exhaust system from the wideband sensor. The lambda is converted to an approximate AFR (Air Fuel Ratio) assuming that lambda 1 = 14.7:1 AFR. The AFR Targets are used to give the fuel trim (fast closed loop fuel adjustment) a target and a multiplier. The Fuel Trim will increase or decrease the injected pulse width in response to the sensed AFR – if it senses too rich, it will reduce the fuel, and if too lean, increase the fuel. The Fuel Trim acts extremely quickly. If there is a consistent amount of fuel trim needed in a particular area, the fuel learning will adapt to that amount, so that the Fuel Trim can work near zero adjustment. The Fuel Learn is saved in the computer’s memory, and can only be cleared by setting the “Reset Fuel Learn” to 1, and then turning off the engine.

Fuel Trim Max = This limits how much extra fuel can be added by the fuel trim.
Fuel Trim Min = This limits how much fuel can be removed by the fuel trim.
AFR Loop Speed = This adjusts how quickly the fuel trim increases and decreases the fuel to achieve the target AFR.
Idle Trim Rate Pos = At Idle, the fuel trim can be slowed to improve the stability of the AFR and engine speed. This value adjusts how quickly fuel is increased (towards richer).
Idle Trim Rate Neg = At Idle, the fuel trim can be slowed to improve the stability of the AFR and engine speed. This value adjusts how quickly fuel is decreased (towards leaner).
Idle Trim Jump Pos = Fuel trim works in a saw-tooth pattern – for example if the engine is rich, there is a slow decrease until lean, followed by a sudden jump rich. This is to keep the actual AFR close to the target – because the fuel film causes a transport delay of the fuel from the throttle body to the cylinder.
Idle Trim Jump Neg = Fuel trim works in a saw-tooth pattern – for example if the engine is lean, there is a slow increase until rich, followed by a sudden jump lean. This is to keep the actual AFR close to the target – because the fuel film causes a transport delay of the fuel from the throttle body to the cylinder.
Fuel Learn rate = The fuel learn can be set to quickly or slowly learn the fuel trim adjustments.
Idle fuel Learn rate = At idle, there is a specific learn value that can be learned more slowly than the normal operation learn rate.
Fuel Learn Max = This value limits how much the fuel learn can learn upwards.
Fuel Learn Min = This value limits how much the fuel learn can learn downwards.
Fuel Learn OFF 1 = This control value will disable fuel learning if it’s set to 1.
Fuel Loop OFF 1 = This control value will disable fuel trim closed loop if it’s set to 1.
Reset Fuel Learn = This control value will reset all fuel learning to 0, if it’s set to 1. The clearing of the learn will happen when the key is turned off and the system is allowed to fully power down.
Display AFR filter = The AFR value displayed in the Dashboard and Data Logging is “filtered” meaning that it shows changes a little slower than it really senses them, to make the value appear more smooth. If more resolution is desired, increase this number to make changes appear more quickly. This value only applies to AFR’s displayed while the throttle is OPEN.
Disp AFR filt idle = The AFR value displayed in the Dashboard and Data Logging is “filtered” meaning that it shows changes a little slower than it really senses them, to make the value appear more smooth. If more resolution is desired, increase this number to make changes appear more quickly. This value only applies to AFR’s displayed while the throttle is CLOSED.

6 comments on “AFR CLOSED LOOP

  1. My AFR displayed in data logging always indicates 14.7…. never changes. I’ve changed targets, but the AFR never approaches those (target) values. At the same time, the lambda value is always at 100, very very seldom deviates from this value. I’m thinking that my O2 sensor isn’t functioning correctly. Would you have advice on what might be happening… am I on the right track?

    1. Check the fault codes as well as check the oxygen sensor wiring lead. It does not appear to be working.

  2. What temp does the system go in closed loop?

    1. 120 degrees

  3. MY AFR TARGET SAYS 13.6, HOW DO I ADJUST IT TO RUN LEANER AT THE OPTIMAL 14.2 YOU SUGGEST? ENGINE IS A 500 HP CHEVY PERFORMANCE 502. UPON INITAL START CAR FIRES RIGHT UP THEN DIES. I HAVE KEYED IT ON A FEW TIMES TO CYCLE THE INJECTORS THEN ALL SEEMS FINE. WHAT ADJUSTMENT CAN BE MADE? HOW DO I GET AN UPDATE. THANKS!

    1. Adjusting the AFR target is very simple. Go to GO EFI TUNING then to AFR TARGETS. The Idle AFR target is the first option.

      Check your white wire for 12 volts during cranking.