Edelbrock Pro-Tuner, User Manual

Page: 13 / 235

Installation and Setup 13
to estimate the airflow through the engine. The air fuel target table is used in
conjunction with this calculated airflow to control the injector pulsewidth. The
MAP-N
strategy uses a base fuel map that varies as a function of engine speed and manifold
pressure. The desired base injector pulsewidth is displayed in the table. The Alpha-N
strategy uses a base fuel map that varies with engine speed and throttle position. The
desired base injector pulsewidth is displayed in the table. The
Alpha-N strategy works
very well for engines with very large camshafts that exhibit very low idle vacuum. The
table below summarizes the advantages and disadvantages to each control strategy.
Modeled Speed Density MAP-N Alpha-N
Advantages
·
If properly setup, does
not require tuning of
temperature based trim
tables
·
Direct measurement of
engine load (assuming
the VE table is accurately
defined)
·
Can adjust for changes in
engine tuning
requirements if used with
optional mass airflow
sensor
·
If properly setup, will be
more consistent as
operating conditions
change
·
Relatively quick and easy to
tune
·
Base fuel map in units of
injector pulsewidth
· Very common tuning method
used in many available
aftermarket EFI systems.
·
Works well and easy to tune
for boosted applications
·
Easy to modify calibration if
larger injectors installed
·
Works well for large overlap
camshafts Not affected by low
idle vacuum signal
·
Relatively quick and easy to
tune
·
Base fuel map in units of
injector pulsewidth
·
Easy to modify calibration if
larger injectors installed
Disadvantages
· Requires an accurate
volumetric efficiency
table
·
Fuel control units more
difficult to understand
·
Mass airflow sensor (if
used) difficult to retrofit
onto older engines
· Does not work well with
large overlap camshafts due
to low idle vacuum
·
Requires temperature based
trim tables
·
Indirect measurement of
load
·
Calibration could be
inconsistent if trim tables are
not properly tuned
· Idle mixture affected by
closed throttle TPS voltage
drift
·
Requires temperature based
trim tables
·
Indirect measurement of load
·
Does not work well with idle
air control motors.
·
Calibration could be
inconsistent if trim tables are
not properly tuned
The engine management system requires sensor data to maintain efficient operation
under various conditions, and to provide feedback to the ECM regarding the current
operating conditions. The sensors needed for basic operation include: ECT (Engine
Coolant Temperature),
IAT (Intake Air Temperature) or (Charge Air Temperature), TPS
(Throttle Position Sensor), CTS (Crankshaft Trigger Sensor), MAP (Manifold Absolute
Pressure) sensor, and O2 (oxygen sensor). Other sensors can be added for additional
control information or data acquisition; however, the sensors listed are the minimum
ones required for basic engine control with this system.
When calibrating an engine, the basic goals are to optimize torque and minimize
fuel consumption at every speed and load point.
However, there are limits to how
far one can go with this in actual application. In practice, you will be constrained by other
factors and may be limited to values that insure running quality and reliability. This is
called the “calibration window” for that condition. We will discuss cal windows later on.
As you proceed, It is very important to understand that engines will attempt to run in