What is a direct gasoline injector engine? How does it work? What are the main advantages and problems with GDI TSI or FSI engines ?
Direct Gasoline injection (Gasoline Direct injection /GDI) is a fuel injection system that injects gasoline directly to the combustion chamber. There is one fuel injector per engine cylinder, as with engines with Multi Point Fuel Injection (MFI). The injectors are located on the cylinder head and not the intake manifold. This means that fuel is directly sprayed into the combustion chamber and not the intake manifold.
The intake valves are completely bypassed and the fuel enters the cylinders in the form of steam. It can be injected at any stage of the suction timing. Low load engines may prevent fuel injection at certain points in the compression timing. The air/fuel mixture is compressed as the piston approaches the top dead center. A spark ignites the mixture. The piston is forced down by the pressure and heat created by the exploded mixture of fuel and air. The exhaust timing is when the combustion exhaust gases are expelled from the cylinder.
High Pressure Gasoline Injectors
Direct injection systems require very high pressure. Multipoint injection systems operate at 40 to 60 PSI (2.75 – 4.13 bar), whereas direct injection systems can operate at up to 2200PSI (150 bar). You will need to apply more pressure to release the pressure trapped in the cylinder and provide higher density fuel within a short period of time.
MFI (conventional sequential injection system): The injectors are located near the connection of the intakemanifold to the cylinder head. Fuel is injected directly behind the intake valves. Along with the incoming oxygen, fuel vapor is drawn into a combustion chamber. They are compressed and mixed together, then ignited by a sparkplug. In GDI systems, air is not drawn from the intake valves. The fuel is directly injected into the combustion chamber during compression.
Direct Petrol Injection engines don’t have a throttle. These engines don’t require a throttle to regulate engine speed or power. The ECU controls each cylinder’s fuel injection timing and amount by controlling the injectors. Eliminating the throttle ensures that there is no restriction on air entering the engine, and there is very little to no vacuum in its intake manifold. This reduces the pumping losses from the throttle plates and intake vacuum, allowing the engine to run more efficiently.
Compression causes the piston to rise and fuel is injected into each cylinder. The timing of the injection depends on engine speed, RPM, and operating conditions. Some cases, such as going too slow, may result in fuel not being injected until it reaches the top. To increase the engine’s power, you can make fuel injections 2-3 times after the first mixture ignites. Multiple injection is also known as multiple injection. This could be a pre-injection, followed by a main inject. The amount of fuel injected is not increased in this instance. Instead, the exact amount of fuel is injected to increase efficiency.
Direct Gasoline Injection Systems have many advantages
Direct fuel injection allows for the engine to produce more power and consume less fuel. Under light loads and cruising conditions, GDI engines can withstand extremely low fuel mixtures (upto 40:1) They offer an average 15 to 20 percent fuel saving compared with multi-point fuel injection systems.
GDI engines have a greater ability to precisely control the fuel mixture, giving the engine what it needs. This allows them to achieve ideal static compression ratios. The compression ratio for the Buick 3.6L V6 engine is 11.3. This increases combustion efficiency and boosts power. Mazda Skyactiv-G 2.5L and 2.0L engines have a 14 to 1 compression ratio, which allows for greater efficiency. GDI engines are more powerful than multi-point injector systems.
Problems in Direct Gasoline Injection Systems
GDI engines may be more sophisticated technology, but that doesn’t necessarily mean they are easier to use. The fuel is sprayed directly into a combustion chamber. This causes carbon and soot to build up on the valves. Over time, a layer of carbon builds up on the intake valves. This carbon layer blocks the valves’ ability to close and causes leaks. The engine can misfire, lose power and even stop working altogether. Airflow can also be restricted by carbon buildup at the intake valves. It can also reduce performance and cause engine to consume more fuel. Carbon deposits can be removed from intake valves and forced out of combustion chamber during exhaust timing. Carbon can also cause damage to turbocharger blades if the engine is equipped with a turbocharger.
Soot deposits tend to be more prevalent in GDI engines that are used for short trips. The intake valves are not hot enough to heat the deposits. High temperatures can cause deformations, such as melting or warping of the valves. Carbon buildup can accelerate if the valve seals leak oil.
To remove carbon deposits, chemical cleaner sprays are available. To remove carbon deposits, it may be necessary for the cylinder head of the machine to be removed.
Direct Gasoline Injection systems can inject fuel at either the intake stroke or at the compression stroke. This depends on the engine’s operating conditions. The compression stroke fuel injection produces a rich mixture close to the spark plug, injector and other parts of the engine. A lean mixture farther away is produced. Because the fuel has only a short time to react with the air, the fuel prior to ignition is very fast. This can result in larger soot particles.
Mitsubishi, Audi, BMW and Ford have models with direct-injection engine technology.
