9
NOTE:
Once the TPS and mechanical idle have been set, you are ready to tune the system.
TUNING THE DIGITAL ECU FOR PERFORMANCE:
DANGER! NEVER MAKE ANY ADJUSTMENTS TO THE POTENTIOMETERS ON THE FRONT OF THE DIGITAL ECU WHILE THE
VEHICLE IS IN MOTION. BE SURE THAT THE VEHICLE IS IN PARK OR NEUTRAL WITH THE EMERGENCY BRAKE
SET. FAILURE TO DO SO MAY RESULT IN PROPERTY DAMAGE, PERSONAL INJURY, AND/OR DEATH.
WARNING! The adjustment knobs on the front of the ECU are precision manufactured parts and do not require a great deal
of force to turn. Do not apply excessive force to the adjustment knobs. Full adjustment range for the knobs is 3/4
of a turn.
WARNING! Initial tuning of the system should be completed in an area free of traffic, such as in a large parking lot. Do not
attempt to tune this system on a busy road, where a possible stall may result in an accident.
NOTE:
A small change in the adjustment knob settings will have a large effect on the amount of fuel delivered to the engine under
various operating conditions. Make small adjustments to the adjustment knob setting when tuning the system.
NOTE:
Holley recommends the use of a Rich / Lean indicator that will provide information relative to the air and fuel delivery to the
engine when tuning the system. A Rich / Lean indicator with an Oxygen Sensor is available from Holley as Part #534-51 and
without an Oxygen Sensor as P/N 534-50. Use P/N 534-50 if you have already installed a closed loop kit.
NOTE:
When tuning the system for future closed loop operation, all potentiometer settings must be set slightly richer then
stoichiometric in case an oxygen sensor failure should occur. This will prevent damage to your engine due to lean operating
conditions.
NOTE:
The tuning of the digital ECU is critical in the operation of the fuel injection system and is best accomplished by using a
tachometer. If your vehicle is not equipped with a tachometer, Holley highly recommends one be used. To adjust, follow the
instructions carefully.
TUNING THE MAIN
As described earlier, the MAIN adjustment knob controls the fuel delivery across the entire operating range by raising or lowering the
fuel delivery 50% above or below the values programmed at the factory. Therefore, adjustments made with the MAIN adjustment knob
will affect the fuel delivery in all modes of engine operation.
1.
Disconnect the closed loop harness, if installed, from the rear of the digital ECU. Initial tuning should be completed with the
system operating in open loop mode.
2.
Start the engine and allow the engine to reach operating temperature.
3.
Once the engine has reached operating temperature, set the parking brake and depress the brake pedal. Increase engine speed
until the engine operates at 3000 rpm and hold the accelerator pedal in this position.
4.
Turn the adjustment knob labeled MAIN, clockwise until the engine rpm reaches a maximum value and the engine rpm just begins
to drop. If your vehicle is equipped with a Holley rich / lean indicator, adjust the MAIN adjustment knob until the green center light
on the unit remains stable.
5.
Rotate the main adjustment knob counter-clockwise back to the point where the engine rpm started to drop, until maximum engine
rpm is once again achieved.
6.
Let off the throttle and allow the engine to return to idle.
TUNING THE IDLE
Adjustments made to the IDLE adjustment knob will affect the area of the fuel map that relates to the idle operation of the vehicle.
1. Turn the IDLE adjustment knob either clockwise or counter-clockwise until maximum engine rpm is achieve and the engine idles
smoothly. If you are using a rich / lean indicator to tune the system, turn the IDLE adjustment knob until the green center LED is lit.
