fuel injection - fuel economy

Fuel injection has become popular due to the emission restrictions made by the epa. The fuel can be controlled much more precisely, due to all the information presented by the sensors to the ecu. There are different types of fuel injection systems. The first progression was to a throttle body setup. The system was simple and had the advantages of precise control. Unfortunately this system has alot of short comings, being that the fuel was being put in the engine in the same location as the carb. The problem with this is that the fuel “puddles” or drops out of suspension and collects on the intake manifold walls. As the engine demands more power (air) the extra airflow pulls the puddled fuel into the cylinders. When the engine stays at a constant speed the ratio moves from lean to rich inconsistantly. Another problem with this setup is that the fuel still travels through the manifold. Intake manifolds are inconsistent and often flow different amounts of air into different cylinders. This leads to cylinders changing from rich to lean.

 

A better system is called multi-point fuel injection or port injection. It delivers the fuel through injectors that sit in the intake manifold close to the cylinder to eliminate puddling. Many systems have individual maps for each cylinder to optimize every one. Another atvantage is the amount of pressure is closer to 40 psi. This atomizes (mixes)the fuel better with the air, which burns more completely in the cylinder. This uses all the fuel instead of not burning some. The throttle body has a problem doing this because it only used about 7 psi which meantnot having a fine mist delivered to the engine.