New CAFE standards specified by the EPA and NHTSA require improvements in fuel economy over the next decade.
To meet these requirements OEM’s are using several approaches. One of these is GDI (Gasoline Direct Injection).
GDI is different from normal injection in that the fuel is injected directly into the cylinder at it’s hottest point near the spark plug. Previous injection systems allow the fuel to go in through the intake valve with the air.
Direct Injection has been around for a while with diesel motors. Diesel fuel is more difficult to atomize. GDI engines are expensive to build. So this is why the delay.
GDI systems burn air/fuel at the rate 40:1 (Air/Fuel). Non-GDI systems 14.7:1. Thus, much less fuel is used. Cleaner emissions also result.
A downside to GDI is that the intake valves are not ‘washed’ with fuel to clean them up. Using Amsoil Performance Improver Fuel Treatment (API) is important as it contains the best detergents.
Steve Dawes, T-1 Certified Direct Jobber, Amsoil Synthetics