What are the disadvantages of multi-point fuel injection?
2 Answers
Multi-point injection has the disadvantage of requiring higher fuel quality, including engine oil; the structure is relatively complex, resulting in higher costs. Multi-point injection has an injector installed at the intake port of each cylinder, controlled by an electronic control unit, which injects fuel individually or in groups into different cylinders. Gasoline is injected in front of the intake port of each cylinder and then enters the cylinder together with air to form a combustible mixture. Multi-point injection is relative to single-point injection. Single-point injection refers to a system where only one nozzle is responsible for injecting fuel into all cylinders. The nozzle is located on the intake pipe before it splits into the intake manifold, and the amount of fuel injected depends on the throttle position. Due to the varying lengths and positions of the intake manifolds, the amount and timing of the fuel mixture injected into each cylinder are inconsistent, leading to differences in the working conditions of each cylinder. The advantage of multi-point injection is that it allows precise fuel injection through the accurate control of the fuel pump by the vehicle's computer, which is why it has replaced carburetors as the preferred tool for automakers to meet strict emission requirements. Additionally, it offers higher combustion efficiency, enabling the same displacement to release greater power. It can also employ sequential injection, allowing more precise control of the air-fuel ratio compared to single-point injection. Therefore, multi-point injection engines have better emissions and are more fuel-efficient.
Owners who have used it may feel the most deeply that the main drawbacks of multi-point fuel injection systems lie in later maintenance and costs. Each cylinder has its own injector, making it more prone to carbon buildup and clogging, especially in northern China where fuel quality is poor in winter, and cleaning can cost several hundred yuan. With numerous parts and a complex system, electronic control failures are hard to repair, leading to high failure rates that affect driving. The initial vehicle price is high, and repair costs are also steep, making it unfriendly for those on a tight budget like me. Compared to single-point injection, multi-point systems are less efficient, wasting fuel and easily causing engine vibration. I recommend regular maintenance, but even then, minor issues like insufficient power often occur, resulting in poor overall cost performance.
