SMT8-X TECHNICAL MANUAL

Perfect Power Online Manuals.

 

Support for your SMT8-X Unit.

WIDE BAND AFR MODIFICATIONS

This feature allows the ‘TUNING’ of two BOSCH LSU4 sensors. The tuning is independent of the two narrow band channels. Both channels are mapped by the same modification.

 

 

ASSOCIATED PINS

 

WAFR1 Pin 3 of 14
WAFR2 Pin 4 of 14

 

 

WIDE BAND CONNECTIONS

SMT8-X Piggy-Back Unit - Wide Band Connection Wiring

 

 

WAFR1 IP (Red) LSU-4 Sensor #1
WAFR2 IP (Red) LSU-4 Sensor #2

 

 

WIDE BAND SENSOR

 

 

The LSU-4 sensor is in essence a narrow band sensor, which is ‘tuned’ by a small current to 14.7AFR. The amount and direction of the tuning current determines the actual AFR in the exhaust gas. This in turn means that at 14.7 exhaust AFR the tuning current is zero, and the probe (Red wire) is 0.45V above the IP terminal.

 


Therefore the voltages on the sensor are meaningless, but the current through the calibration resistor is a measure of the AFR.

 

 

MAPS

 

SMT8-X Piggy-Back Unit - F3 - Narrow AFR Map

SMT8-X Piggy-Back Unit - F4 - Wide AFR Map

The entered Map modification values are not precise. The reason for this is that current/AFR ratio is nonlinear. However, the error is relative small when compared to the AFR range.

 

 

AFR TUNING

 

You can tune the NARROW and the WIDE BAND probes separately by entering numbers in to the respective maps.

Positive numbers in the narrow band map make the mixture APPEAR richer, thus the ECU will reduce the fuel.

Positive numbers in the wide band map will make the mixture APPEAR leaner, thus the ECU will add fuel to restore the closed loop target.

 

 

TUNING BOTH SETS OF SENSORS FROM ONE MAP

 

The Wide band sensors are before the CAT. The entries in this map can be used to tune the narrow band probes.

 

Requirements:

Set the SYSTEM DEFINITION: Link enabled
Set the SYSTEM DEFINITION: Inverse link (as required)
Set the PARAMETER: Link Multiplier to a value greater then ZERO

 

Tuning operation:

  • Display the narrow AFR value without and tuning.
  • Affect the wide AFR by a small amount and observe the changes in the narrow display. Reverse the direction if indicated, and change the multiplier up or down to bring the narrow band display in to range again.
  • The narrow band display must stay reasonable at 14.7 AFR with light throttle.