AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 115)

Page 115 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
Non-Linear Load and RPM Setup
EFI Sensors
TPS (Throttle Position Sensor)
The TPS determines the position of the throttle blade in the throttle body. This input is used to
determine rate of throttle angle change (both positive and negative), idle position, and discrete
throttle opening for TPS-based calibrations. The TPS typically is a potentiometer bolted to the
end of the throttle shaft. Rotating the throttle varies the resistance, and consequently, the
voltage returned to the ECU is a function of that resistance. The rate of change is measured to
determine whether a vehicle is accelerating or decelerating. Based on this rate of change, the
proper amount of fuel is either added or subtracted from the base calibration to achieve the
proper amount of fuel for the operating condition.
The TPS is also used to determine if the vehicle is idling. When the throttle is at rest, the
vehicle is considered to be either idling or under heavy deceleration, and the fuel and ignition
calibrations are adjusted for optimum idle characteristics. The TPS can be used as a calibration
input if the AEM EMS is set up to be a throttle position vs. RPM based mapping scheme. This
type of mapping allows the tuner to set up the fuel map based on the throttle angle from 0 to
100% on the Y-axis of the map, with the X-axis being RPMs. This type of mapping is usually
best for naturally aspirated racing engines with individual runner inlet manifolds and no plenum
chamber or very aggressive cams.