FSI is the abbreviation of "Fuel Stratified Injection", which means fuel stratified injection, also known as "gasoline direct injection". It is a revolutionary innovation technology that Volkswagen transplants its pioneering direct injection technology in the diesel engine cylinder to the field of gasoline engines. In layman's terms, gasoline and air are injected into the combustion chamber separately, and the air-fuel ratio is more accurately controlled, resulting in more complete combustion, thereby achieving the goals of being more fuel-efficient and environmentally friendly
Representative of FSI gasoline direct injection technology The latest development direction of gasoline engines. Normal engines use gasoline and air to be mixed in the intake manifold and then injected into the combustion chamber. Gasoline direct injection technology directly injects gasoline into the combustion chamber, which reduces fuel consumption through uniform combustion and stratified combustion. , the power has also been greatly improved.
The FSI engine uses a variable intake manifold, and the electronic system controls the required air flow, achieving throttle-free deterioration adjustment and improving charging efficiency, thereby obtaining higher power per liter, while the engine The dynamic response has also become more direct and rapid.
The variable intake manifold is equipped with an intake guide valve whose position is adjusted by a stepper motor, so that the flow and swirl of air can be appropriately controlled according to engine speed and load. The fuel and air mixture is evenly distributed in the combustion chamber, which naturally increases power and enables rapid and complete combustion at every operating point within a wide engine speed range.
FSI technology injects fuel directly into the combustion chamber. The position of the fuel injector is directly above the combustion chamber from the original intake manifold. The high-pressure electromagnetic fuel injector controls the fuel injection time. Within a thousandth of a second. All cylinders use a pressure accumulator - the pressure rail system. The nozzle can control the fuel supply with millisecond accuracy and injection pressure up to 110 bar, while the injection pressure of the manifold injection system is only between 4 and 6 bar.
The injection time of the fuel injectors is controlled within one thousandth of a second, and the fuel is directly injected into the combustion chamber at the most appropriate time. Through the special geometry of the combustion chamber, the mixture can produce a higher Strong vortex makes air and gasoline fully mixed. Then the area around the spark plug can have a richer mixture, and other surrounding areas have a leaner mixture, ensuring that lean combustion can be achieved as much as possible under smooth ignition. This is the essence of layered combustion. Another benefit of the direct injection engine is that it isolates the ignited mixture from dissipating heat to the cylinder wall and cylinder head, thereby reducing the heat loss of the engine.
The characteristic of the direct injection gasoline engine principle is that it can adopt two different oil injection modes, namely stratified oil injection and uniform oil injection modes. In the half-open throttle state, the stratified fuel injection method can give full play to the fuel economy, because only around the spark plug, the fuel-air mixture rich in gasoline that can be triggered is needed. In other places in the combustion chamber, only a fuel-air mixture containing a high proportion of air is injected. Under daily driving conditions, the fuel-saving performance of direct-injection gasoline engine technology will be even more significant because the driver can continuously switch back and forth between the two modes of stratified oil injection and uniform oil injection. Direct-injection gasoline engine technology enables the principle of stratified injection because it controls the injection process in the combustion chamber and injects fuel directly before triggering is complete. This significantly reduces the amount of fuel required for combustion – the most important prerequisite for the economic efficiency of FSI engines.
The four-valve cylinder head adopts a low-friction cam roller lifter valve mechanism. Its air inlet geometry is derived from the naturally aspirated FSI engine, which can generate stronger swirl flow and ensure The accuracy of the work can also improve the anti-knock level, thereby improving the working efficiency of the engine. Therefore, the compression ratio of a turbocharged engine can reach 10.5:1. This number can only be achieved by naturally aspirated engines. Compared with manifold injection engines and conventional turbocharged engines, this compression ratio and the direct injection of gasoline Superior performance is a key factor in improving thermal efficiency.
The two balance shafts that rotate at double the speed of the crankshaft offset the inertia from the internal motion of the engine and ensure a high standard of low engine noise, which is the best that a four-cylinder engine can achieve. The most significant advantage of gasoline direct injection technology is that it provides greater output power and torque while improving fuel economy and reducing emissions.
While providing greater output power and torque, the FSI engine further improves the engine's fuel economy and reduces emissions. Compared with traditional engines of the same displacement, the fuel consumption of FSI engines is significantly reduced, which highlights its advantages in today's increasingly scarce energy environment.
Applications over the past few years have proven that under the same displacement, FSI is significantly more dynamic than traditional MFI (multi-point fuel intake manifold injection), outputs higher power and torque, and consumes less fuel. It is reduced by 15%, thereby achieving the perfect combination of engine power and fuel economy. It is the most mature and advanced direct fuel injection technology in today's automotive industry engine technology, and leads and extends the development trend of gasoline engines.
Inspired by the success of the FSI series engines, Volkswagen subsequently launched the TFSI series engines with turbochargers.
The TFSI series engines retain the abbreviation FSI, and it goes without saying that it is still "gasoline direct injection". However, the stratified charging working mode was abandoned and dedicated to improving power and torque. Instead, there is a homogeneous charge working mode and a turbocharging effect. In other words, TFSI has canceled the layered mode and nitrogen oxide sensor, and focuses more on the driving pleasure, traction and extraordinary economy brought by higher power and speed.