Piezo Direct Injection System for Gasoline Applications

Improving fuel injection is aimed at better performance from less gasoline, meaning enhanced efficiency, economy, combustion, and emissions.

Injection in gasoline engines previously involved a homogeneous charge or spray into the combustion chamber. It was first done into the intake manifold. Subsequent direct injection into the combustion chamber used solenoid activated injection. In that case, the needle lifts into the injector, there is only a single injection per combustion cycle, and the fuel sprays into the chamber in a homogeneous charge. This wastes fuel and results in incomplete combustion of the excess.

Continental has for the first time applied piezo activation to direct injection in high revving gasoline engines. The innovation was accomplished in response to a challenge from BMW to create a stratified charge and lean burn.

Only the fuel necessary is injected and is directed only where combustion actually occurs. The innovation is a needle that is directly piezo activated to open into the cylinder, resulting in a hollow cone spray, and the possibility of two injections per cycle due to direct piezo activation. The stratified charge is stable without respect to engine load, an optimal lean burn circumstance. Additional innovations included a new type of seal, unique welding techniques to suit the metals necessary, and thermal expansion compensation.

Result is estimated at up to 20% fuel savings, 40% reduction in hydrocarbon emissions, and 12% reduction in CO2 emissions, while doubling the rpm range for engine efficiency.

Initial adoption for piezo direct gasoline injection was in BMW’s 4 and 6 cylinder engines, and BMW is rolling out this system across its engine range.