Edelbrock 3670 User Manual - page 123
Basic Tuning with the Pro Tuner System
123
Tuning Tips:
Spark advance is specific to the engine combination. However, trends can be applied
across various engines. The goal in determining optimum spark advance is to use the
minimum spark advance required to maintain best torque at each speed/load point.
Note that you can draw a comparison between a typical mechanical advance curve (for a
carbureted application) and a fully programmable 3-D table as shown above. The table
above is set up such that engine vacuum has no influence on the ignition advance. The
ignition timing increases as RPM rises. The advantage to a fully programmable table is
you have no mechanical constraints. You simply enter the exact ignition timing desired
at each RPM/load point on the 3-D table.
Light load conditions will require more spark and allow leaner air/fuel ratios for improved
part throttle economy. Heavy loads will need less because the richer mixture required for
best power will have a faster burn rate. Many engines will also be limited by detonation
limits.
For best idle, have the cells immediately around the base idle point to be "Flat", in other
words, use the same value or minimally sloped values in the cells that the engine
typically idles in. Steep spark changes around the idle point will cause instability and
surging that cannot be tuned out with the idle controller settings.
As the tuner you will have to optimize the fueling and ignition advance by scanning the
parameters as described in the concepts section. Start at low speed and conservative
values. Optimize these values and work your way to higher loads and speeds. As the map
takes shape, with experience you will be able to determine how the map will contour. If
you have a good spark curve from a standard distributor for your engine, you can use
that data to create a "backbone" for the map which you can work outward from. As with
the fuel maps and individual cylinder maps; the more instrumentation you have, the
better you will be able to generate an optimized calibration.