GDI

GDI (Gasoline Direct Injection) is an advanced engine fuel delivery technology. Unlike conventional Port Fuel Injection (PFI), which injects petrol into the intake manifold to mix with air, GDI technology uses a high-pressure fuel pump and high-pressure injectors to spray petrol directly into the engine's combustion chambers at extremely high pressures (typically ranging from 150 bar to 350 bar, or even higher). GDI allows precise control over injection timing, fuel volume, and spray patterns, significantly enhancing combustion efficiency, power output, and fuel economy, while effectively reducing harmful exhaust emissions under low-to-medium loads.

Core Technical Architecture and Operating Principle

The technical architecture of a GDI system mainly comprises a high-pressure fuel pump, high-pressure common rail, high-precision high-pressure injectors, an Engine Control Unit (ECU), as well as specially contoured combustion chambers and piston crowns:

High-Pressure Mechanical Pressurisation and In-Cylinder Direct Precision Injection:

Driven by the camshaft, the mechanical high-pressure fuel pump in the engine bay pressurises the petrol and delivers it to the high-pressure common rail. The injectors are mounted directly on the cylinder head, with their tips extending straight into the combustion chamber. During the intake or compression stroke, the ECU controls the injectors to open instantaneously under high pressure with microsecond precision based on current engine load and RPM, spraying finely atomised micrometre-scale fuel droplets directly into the cylinder for highly efficient mixing with fresh air drawn in by the intake valves. 

Stratified Charge Combustion and High Compression Ratio Thermal Efficiency Optimisation:

Under light-load conditions, the GDI system can operate in a "stratified charge combustion" mode—forming an easily ignitable rich air-fuel mixture around the spark plug while keeping the surrounding mixture near the cylinder walls lean, thereby significantly reducing pumping losses and saving fuel. Under full-load, wide-open-throttle conditions, the system switches to a "homogeneous mixture" mode, which works in tandem with the optimised piston crown geometry to generate strong in-cylinder tumble and swirl, delivering exceptionally robust power output.

Safety Specifications and Physical Limitations 

Strict prohibition against neglecting regular use of quality clean fuel or skipping high-pressure fuel system maintenance, which leads to severe intake valve and injector carbon buildup:

Because GDI injectors are directly exposed to the high temperatures and pressures inside the combustion chamber, and petrol no longer washes over the back of the intake valves, the rear of the valves is highly prone to severe carbon buildup caused by Exhaust Gas Recirculation (EGR) and Positive Crankcase Ventilation (PCV) oil vapours. Running the vehicle on substandard petrol or failing to clear carbon deposits over extended periods is strictly prohibited, as this can cause improper valve sealing, clogged injectors, engine knocking, rough idling, and engine misfires.

Strict prohibition against disassembling high-pressure fuel rails or injectors while the engine is hot or when fuel lines remain under pressure:

Fuel operating pressures in GDI systems can reach hundreds of bar, far exceeding those of conventional fuel systems. It is strictly prohibited to loosen high-pressure fuel lines or remove injectors while the engine is hot or before the system has been professionally depressurised. Escaping high-pressure fuel can easily trigger catastrophic fire hazards, and high-pressure fuel penetrating the skin can lead to severe subcutaneous tissue necrosis and infection.