How does it Really Work? have you asked how?
Apparently some people are clueless on the technology behind Fuel-Injection. They read articles about fuel-injection, but they never see anything about how fuel-injection actually works. It get even worse if they start talking about remapping and reprogramming...
Although fuel-injection can be quite a complex system at the design and engineering level, in concept, it's actually pretty simple. Its primary benefit is its ability to control the fuel-air mixture more precisely under more varied operating conditions than a carburetor ever can.
A carburetor's operation is dependent upon intake-tract vacuum, called a “signal,” created by the down-stroke of the piston. The vacuum sucks air in through the intake inlet, and the rapid movement of that air over passages in the carburetor's venturi siphons fuel up out of the float bowl and into the intake stream. If all the jets and passages are properly calibrated for the engine, the fuel mixture should be correct for the prevailing conditions.
But a carburetor doesn't self-adjust very well. If the signal is weak-such as when the throttle is quickly turned wide-open at very low rpm there often is not enough intake vacuum to draw sufficient fuel up out of the float bowl, so the engine sputters and wants to die. At high altitudes, where the air is thinner, the engine runs too rich; at exceptionally low altitudes it runs too lean. Same with changes in temperature: When it's hot, the mixture tends to be rich, and when it's colder, it tends to be lean.
A fuel-injection system, however, does not rely on intake vacuum, and it can adjust itself – within predetermined parameters, at least – to changes in altitude and temperature. It uses relevant data gathered from key points around the engine to determine the proper fuel mixture, regardless of air temperature, air density or the amount of vacuum present in the intake tract.
