One of the most important new technologies to come to spark ignition engines in recent years is direct fuel injection. Audi was one of the pioneers in applying the system to road cars after using it on the Le Mans-winning R8 earlier this decade. More recently, General Motors has used it on the 2.0L turbo four cylinder that powers a number of performance models as well as the 3.6L V6 in used in Cadillacs and crossovers. With two new high volume DI engines coming for the 2010 model year, Chris Meagher, chief engineer for the EcoTec four cylinder engines, has published a post on the Fastlane blog as well as video discussing direct injection.
Among the key benefits of DI are more precise fuel metering as well as a more homogeneous mixing of air and fuel. That helps reduce wasted and unburned fuel. The other component is that a higher compression ratio can be used without causing problems with pre-ignition and knock. By compressing only air, there is nothing to burn as the air heats up. When the fuel is sprayed directly into the cylinder, the temperature is reduced as the liquid fuel vaporizes. The result is more power from less fuel and less displacement. Smaller engines also mean less mass, further helping efficiency. Check out Meagher's video after the jump.