SMT8_4 TECHNICAL MANUAL

Perfect Power Online Manuals.

 

Support for your SMT8 V4 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.

 

 

ASSOCIATED PINS

 

WB1 Pin 10 of 10
WB2 Pin 9 of 10

 

 

WIDE BAND CONNECTIONS

 

SMT8V4 Piggy-Back Unit - Wide Band System Wiring

 

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 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.

 

 

WIDE BAND OUTPUT CALIBRATION

 

This is necessary, because the electronic circuit is not perfect: it has an OFFSET error! The calibration is relative simple:

 

  • Connect WAFR1IN to IP of the LSU-4 sensor
  • Make sure that the Wide band maps contain all zero (no modification)
  • Connect a voltmeter between the WAFR1IN and the WB1OUT pins
  • Adjust the ‘Zero output offset’ (parameter) until the voltmeter reads zero


Perform the same on the second channel (if you use it).

SMT8V4 Piggy-Back Unit - ShiftF1 - Parameters

 

MAPS

SMT8V4 Piggy-Back Unit - F10 - WB AFR Modification 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.