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Smart Tuner SMT8 - Tuning AFR via Dual Lambda | Application Note : AN 1.3


Perfect Power Application Notes.


Application Note : AN 1.3


This application note describes the various methods of tuning the CLOSED LOOP LAMBDA signal. Narrow or Wide band lambda can be tuned.


Why would you want to tune closed loop lambda? Due to the ongoing emission problems, the demand for manufacturers to run permanent closed loop is increasing. What this means is that when you select settings for the engine, for example : tuning fuel, the lambda sensor will recognize these changes and the ECU will correct the air/fuel ratio back to what they were previously.
Using the SMT8, you can now tune lambda. This means you would run the lambda signal through the SMT8 for Narrow band and tee onto the signal for Wide band. When you make a change, the ECU looks at the lambda and changes itself to your new settings. The standard ECU still see lambda as correct but in actual fact the fuel settings have changed.

SMT8 Features and Wiring

The SMT8 has dual Narrow band and Wide band inputs. They both use a 384-site map, which is added to two 24-row side maps of engine temperature map and manifold pressure. The map sites are selected by the throttle position (or any other load signal) and the RPM.
SMT8 Piggy-Back Unit - F7 - Narrow AFR Modification
SMT8 Piggy-Back Unit - Wide Band AFR Modification Map
The wiring of the SMT8 for the NARROW BAND LAMBDA INPUT is shown in the diagram below :
SMT8 Piggy-Back Unit - Narrow Band Lambda Input Wiring
The wiring of the SMT8 for the WIDE BAND LAMBDA INPUT is shown in the diagram below :
SMT8 Piggy-Back Unit - Wide Band Lambda Input Wiring



Most of us spend 90% of the time while driving a car "cruising" due to speed and traffic restrictions. The SMT8 is the ideal tool to improve the cruising performance, while enhancing the power output at full throttle when overtaking. This can be done by intercepting the "CLOSED LOOP LAMBDA".