The Grunt Box - Trigger Adjustment
Important note:   The Gruntbox as deliverered should not require any adustment. If one is to attempt to lower the trigger point it is important to keep in mind that it is possible  to cause overfueling in certain conditions which can lead to engine damage.   
  1. With your ignition on, measure the voltage at VTA (from TPS) to the Grunt Box ground point with the throttle completely open.
  2. Determine your trigger voltage by multiplying the wide open throttle voltage by the desired triggeringthrottle percentage. For example, if the reading from step 1 is 4.0V and you wish to trigger the Grunt Box at 60% throttle opening, multiply 4.0 x 0.6 which = 2.4V (this is the setting as delivered)
  3. With the ignition power off, open the Grunt Box by removing the lid screws. 
  4. Making sure not to short out any exposed parts from the Grunt Box to the chassis (including the heatsink lug screw, if metal), turn the ignition power on. From the picture below, measure the voltage at the pin indicated by the yellow circle..
  5. Adjust the trim pot reference voltage by turning the screw indicated by the red arrow; screwing in lowers the voltage, screwing out raises the voltage. Adjust the reference voltage until it matches the value determined in step 2.
  6. Turn off the ignition power and reassemble the Grunt Box.
  7. After test driving the new setting, you may wish to lower or raise the trigger point. Repeat until the enrichment triggers at the desired throttle opening. Keep in mind that setting the trigger too low could resort in overfueling.