AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 198)

Page 198 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
the option VSS Cal * 8 to ON. This will allow more range.
VSS Filter Units: On/Off Description, Used to smooth the speed sensor. Use as first defense.
VSS Hall Falling Units: On/Off Description, Sets falling edge as significant edge.
VSS Hall Rising
Units: On/Off Description, Sets rising edge as significant edge.
VSS Smooth Units: On/Off Description: Used to smooth the speed sensor. This is very
aggressive. This should be used after VSS Filter but only if needed.
VSS Input Units: User Definable InputDescription: Channel of the input for the Vehicle Speed
Sensor. For EMS-4 applications, set to VSS Hall input.
Vehicle Speed Channels
Vehicle Speed Units: Vehicle Speed Description: Displays the current scaled speed of the
vehicle via the vehicle speed sensor.
Tuning the VSS
First, determine which channel the speed input is wired to. For plug n play applications, 99% of
the time it will go to the Vehicle Speed input (also known as "Speedo" or "T3"). For EMS-4
applications, set to VSS Hall.
The edge must now be defined. Select rising or falling edge options described above.
Now, the sensor should be scaled so it reads the actual vehicle speed. Display the Vehicle
Speed parameter and start adjusting VSS Calibration to scale the function. If 256 is not
enough, set VSS Cal * 8 to ON. This will allow more adjustability.
Tuning Tip - A chassis dyno is especially helpful here as they usually have very accurate
roll speed sensors. Use the dyno to hold the vehicle at a constant speed and adjust the
VSS calibration options until the displayed vehicle speed value in AEM Tuner matches
the value displayed by the chassis dyno.