TECHNICAL NOTES ON THE EEC-IV MCU - Auto diagnostics

· Part Throttle A/F Ratio: Controls part throttle A/F ratio based on rpm.
· Wide Open Throttle (WOT) A/F Ratio: Controls WOT A/F ratio based on rpm.
Eectch98-Part5.fm
· Air Charge Temperature (ACT) Multiplier: Richens or leans the fuel based on inlet
air temperature.
· Engine Coolant Temperature (ECT) Multiplier: Richens or leans the fuel based on
engine coolant temperature. In other words, it’s the choke.
· Throttle Position (TP) Multiplier: Richens or leans the fuel based on throttle
opening.
· Manifold Absolute Pressure (MAP) Multiplier: Richens or leans the fuel based on
manifold pressure, either vacuum or boost.
· Transitional Fuel Enrichment (TFE): This richens the fuel when opening the throttle,
like a carburetor’s accelerator pump.
· Injector Offset Adder: This corrects for injector offset; the time it takes for
the injector to open.
· Programmable Output Fuel Multiplier: Richens or leans the fuel based on the output
state of each of the four available output channels. What you hook up to these
channels is up to you.
· Analog Input Fuel Multiplier: Richens or leans the fuel based on the input voltage
of each of the three available channels. You decide what you want these channels
connected to.
Setting up each of these fuel control parameters means the EPEC wants to know when
the enrichment (or leaning) should begin, how much enrichment you want and when to
turn it off. It might ask for an either/or decision, such as, do you want this form
of enrichment if these other three enrichments are already underway? It can be complex,
as there are many layers to go through. There is a stock default setting
saved so you can get back to a standard calibration with minimal keystrokes. Also,
you can save several custom calibrations of your own to save reinventing the
calibration.
The spark functions are:
· Idle Spark Adder/Subtractor: Advances or retards spark based on rpm at idle.
· Part Throttle Spark Adder/Subtractor: Advances or retards spark based on rpm at
part throttle.
· Wide Open Throttle (WOT) Spark Adder/Subtractor: Advances or retards spark based
on rpm at WOT.
· Air Charge Temperature (ACT) Spark Adder/Subtractor: Advances or retards spark
based on air inlet temperature.
· Engine Coolant Temperature (ECT) Spark Adder/Subtractor: Advances or retards spark
based on engine temperature.
· Barometric Pressure (BP) Spark Adder/Subtractor: Advances or retards spark based
on barometric pressure.
· Throttle Position (TP) Spark Adder/Subtractor: Advances or retards spark based on
throttle opening
· Manifold Absolute Pressure (MAP) Spark Adder/Subtractor: Advances or retards spark
based on manifold pressure (load). Requires fitment of a GM MAP sensor.
EEC-IV Technical Notes: Modifications/Upgrades70 last edited: 9/29/98