Gasoline Direct Ignition Engine
• First, the fuel travels via pump from the fuel tank, through the fuel line and into fuel injectors that are mounted into the engine.
• The injectors spray gasoline into the air intake manifold, where fuel and air mix together into a fine mist. At precisely timed intervals, intake valves open, corresponding to the different cylinders of the engine.
• As a cylinder's intake valve opens, a piston in that cylinder descends, sucking the fuel-air mist from the air manifold above into the chamber below. As the piston ascends once more, it squeezes (compresses) the fuel-air mix until it is nearly nine times as dense as it was to begin with.
• Then, that cylinder's designated spark plug fires, igniting the chamber into a high-pressure, high-energy explosion.
• This little bang pushes the piston back down with tremendous force, causing it to turn the crankshaft and ultimately send power to the wheels.
• The ratio of air to fuel as it burns in an engine will have certain, predictable effects on engine performance, emissions of pollutants and fuel efficiency.
• When the amount of air in the mixture is high, compared to the amount of fuel, it's known as a "lean" mixture. When the reverse is the case, it's called a "rich" fuel mixture.
• Direct injection engines use a mixture of 40 or more parts air to one part fuel, written as 40:1.
• That compares to a normal gasoline engine's mix of 14.7:1. A leaner mixture allows fuel to be burned much more conservatively.
• A second efficiency plus for direct injection engines is that they can burn their fuel more completely.
• The fuel can be squirted directly where the combustion chamber is hottest -- in a gasoline engine that means it ends up close to the spark.
• With a traditional gasoline engine, the fuel air mixture disperses widely within the chamber, leaving a substantial amount unburned and therefore ineffective.