What is PGM-FI & ECU?

Programmed Fuel Injection,

or PGMFI/PGM-FI, is the name given by  Honda to a proprietary digital

electronic fuel injection system for internal combustion engines which

injects the right amount of fuel per cylinder based on specific engine data,

available since the late 1980s. This system has been implemented on motorcycle

and automobiles. 

The PGM-FI is one of the core technologies

to attain the goals of clean exhaust gas and fuel economy. An inevitable next

goal is to extend the application of the innovative technique to models in

various categories that respond to a larger number of users. Through the newly

developed compact PGM-FI, Honda increases the application from large touring

models, to the super sport models, and the models targeted towards a larger

number of people.

The Engine Control Unit (ECU) has

sensors which measure the temperatures of the engine, coolant, oil, and outside

air as well as pressure sensors to monitor oil and barometric pressure. Based

on these readings and the location of the throttle, the ECU calculates how much

oxygen and fuel should be mixed for optimal and efficient performance.

With the move from carburetors to fuel

injection, computers have assumed an important role in the proper functioning

of an engine. The level of precise control possible with a ECU  (Engine

Control Unit - computer for running an engine) can not only allow for greatly

improved fuel economy, but can also allow for fine tuning of an engine to a

degree that is arguably impossible with the best carburetors. Many ECUs,

including those made by Honda, do data interpolation, allowing them to

intelligently compensate for engine conditions that fall "between"

known states, allowing for an almost continuously variable response to varying

engine conditions. Additionally, the ECUcan make small corrections to

fuel/timing based on the state of various engine sensors. It is probably fairly

fair to say that from the factory, most manufacturers tune for fuel economy,

emissions and poor quality gasoline as opposed to power and race gas.

Beware of most aftermarket

"chips": more often than not these programs just dump more fuel and

increase timing greatly while doing things like raising revlimiters far beyond

safe levels. There are very limited gains to be had from most "performance

chips." Tuning not "chipping" generally produces usable, real

world gains. That being said, changing the program of a ECU is

generally not that tricky. First, it would probably be wise to focus on some

basics of how ECUs work so that it is more apparent where we could makes

changes to have a positive effect on performance.