Fuel trim is a "fudge factor" if you will. The PCM has a set of tables and modifiers that uses to determine fuel delivery for any given situation as a baseline. But, the PCM also monitors the air/fuel ratio using the oxygen sensors in the exhaust to verify that the fuel delivery is what it expects. Due to build variation in every component in the engine, and changes in wear and buildup that occur over the life of the engine, the actual fuel requirements for a particular engine are determined by taking the base tables, and then taking what the oxygen sensor says and using it to modify the fuel delivery slightly to optimize emissions. The resulting modifier value is stored as short term fuel trim. Over time, the PCM records trends in the short term fuel trim, and adjusts the long term fuel trim value to accomodate it.
Fuel trims are basically what the PCM uses to adapt fuel delivery to the small differences between engines, and the changes that occur over an engine's lifespan.
injector pulsewidth refers to how long each injector is open for each time it delivers fuel. You can take this number and the size of the injector and the number of injectors and determine the total amount of fuel flow for a given number of engine revolutions. injector duty cycle refers to the relative difference between the injector pulsewidth and the amount of time the engine takes to complete its cycle (the full 4-stroke cycle). Exceeding 80% duty cycle is not generally a good idea.
And don't post whore like that, its against the rules.
