SMART TUNER SMT8 - FUEL TUNING AFRIN CLOSED LOOP
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Perfect Power Application Notes. |
Application Note - AN 1.2 |
Introduction
This application note describes the methods of tuning the air fuel ratio of the engine when there is a closed loop narrow band lambda circuit.Purpose
SMT8 Analog and Narrow band Wiring

SMT8 Narrow Band Mapping

The tuning in the narrow band lambda map works as follows : if the displayed incoming AFR is 14.7 (click "Data Display", select the desired item, tick "Small Window") and you wish to make the engine richer by mapping the Analog channel. Make the change to the Ana#1 map so that the AFR now reads 14.2, you will need to offset the Narrow AFR map by entering a positive number of 0.5 into the map so that the outgoing lambda will read as 14.7, the OEM ECU should take no action to remove the extra fuel.
SMT8 Analog Setup

The Analog voltage has three parameters in the "Shift F1" map, they are the "An1 Upper Limit", "An1 Lower Limit" voltages and the "Analog#1 Offset %" percentage. The Upper Limit clamps the maximum voltage that would be returned to the OEM ECU, this works the same for the Lower Limit. The offset percentage will increase or decrease the entire Analog #1 map, so if the engine is too rich across the complete rev range then there would be a negative value entered to lean the engine out.
SMT8 Analog Mapping

Testing if you have control of the fueling is simply done by entering a large number for example 50 into the green cell in the main map during idle and confirming that the engine's pitch changes. The mapping calculation is as follows :
A1OUT | = | AN1IN |
+- ANA1 MAP | ||
+- AN1 ENGT | ||
+- AN1 AIRT | ||
X AN1 AMP |
Please Note : If there is a 0.01 in the Ana#1 AMP side table there will be no modification!
Conclusion