Tuning a Harley Electronic Fuel Injection system

Tuning a modern Harley Davidson Electronic Fuel Injection
system refers to the use of computers and software to produce a fuel
optimization “map” for the engine–designed to optimize the release of
fuel mixtures under varying conditions.

Why Tune Your Harley Davidson EFI System?

Tuning the EFI system of a Harley Davidson motorcycle increases the
efficiency of the Electronic Fuel Injection system by keeping the fuel
mixtures within specific ranges that allow the engine to work best. 
Maximizing the benefits of tuning an EFI system can increase power and
could increase the mileage of the bike. Tuning an EFI system also
allows you to make sure your motorcycles EFI system is properly mapped
to any custom components you have added to your bike. This is
especially important if you have changed the exhausts on a fuel
injected motorcycle, because the correct amount of air being received
by the engine may not be sensed by the EFI’s ECU (Electronic Control
Unit–The brains of the EFI system). This in turn would mean the proper
fuel mixture could not be determined by the computer and the fuel map
of the EFI system would need to be changed to take into account the
differing amount of air.

What Options are Available for Tuning Your Harley Davidson Motorcycle?

There are three different types of tuning aids available to help
motorcycle enthusiasts’ tune the Electronic Fuel Injection system on
their bike. These are pre-designed, downloadable fuel maps for
particular bike component arrangements called ECM (Electronic Control
Module) calibration by Harley Davidson, self contained units that are
attached in series between the bike’s ECM and fuel injectors to change
the signals the ECM is sending to the fuel injectors, and complex
map-based tuning aids for bigger bikes.

ECM Calibration includes fuel maps tailored for power plants
implementing EFI systems provided by Harley Davidson. You can purchase
an ECM calibration at a Harley Davidson dealer and then have it
downloaded into the ECM of your motorcycle for a small fee. In
addition, manufacturers of aftermarket EFI custom components sell down
loadable fuel maps tailored to particular engine arrangements on their
sites.

Add-on units are self-contained devices that can include a few
default fuel maps designed for specific engine/exhaust system
modifications. These units don’t usually involve the use of a computer
for changes. Instead you use a screwdriver to make the changes that
instruct the fuel injectors to make the fuel mixture richer or leaner.
Fuel mixtures need to fall within certain ranges to allow the engine to
function best and the required mixture range required is based on
engine RPM and engine load.

Programmed map-based units include multiple viewable tables
segmented into smaller cells to finely tune the motorcycles EFI over a
huge range of variables. This type of tuning aid is used for
motorcycles above 100 cubic inches and huge cams. Software tuners alter
the internal ECM/EFI programming and Piggyback controllers are
connected to the engine.