What are the differences between direct injection and multi-point injection?
2 Answers
The main difference between direct injection and multi-point injection lies in the fuel injection method. The following are the distinctions between direct injection and multi-point injection: 1. Fuel injection method: Electronic fuel injection can be divided into ordinary electronic injection, single-point injection, and multi-point injection. Essentially, the forms of injection are quite similar—all involve spraying fuel into the intake manifold where it mixes with air before entering the cylinder for combustion. However, the control precision has become increasingly refined. Direct injection delivers fuel directly into the cylinder, where it then mixes with air from the intake manifold before combustion occurs. 2. Their respective advantages: Multi-point injection has a relatively simpler structure, more mature technology, and does not require as high a fuel injection pressure as direct injection. Therefore, the demands on electronic fuel injectors are lower, and the cost is relatively cheaper. In terms of reliability and post-maintenance, it is clearly more economical. Additionally, multi-point injection engines are less demanding on fuel quality. The greatest advantage of direct injection is that fuel is injected directly into the combustion chamber at extremely high pressure. With significant advancements in electronic control systems in recent years, the computer's ability to interpret and control air intake and fuel injection timing has become more precise, enabling stratified combustion and lean combustion. As a result, it offers superior performance in fuel efficiency and power compared to multi-point injection technology. 3. Their respective disadvantages: Multi-point injection engines can form a mixture in the intake manifold, making the intake tract more prone to carbon deposits. However, since multi-point injection sprays fuel into the intake manifold and gasoline itself is an excellent carbon deposit cleaner, it can effectively clean components such as the intake valves, cylinders, fuel injectors, and intake manifold. Therefore, it tends to have fewer carbon deposit issues compared to direct injection. On the other hand, direct injection engines inject fuel directly into the cylinder, making the cylinder more susceptible to carbon deposits (the throttle of direct injection engines is prone to carbon buildup). However, the intake manifold area of direct injection technology lacks a significant amount of gasoline to clean carbon deposits, leading to the accumulation of more carbon over time, which can obstruct airflow. This, in turn, can increase vehicle fuel consumption and reduce power output.
I've been driving for over ten years and have experience with both direct injection and multi-point fuel injection vehicles. Direct injection sprays fuel directly into the cylinder, while multi-point injection sprays fuel at each intake port. With direct injection, I feel the throttle response is quicker, acceleration is more powerful, and fuel consumption on highways is noticeably lower—my car saves 1-2 liters per 100 kilometers. However, in city traffic jams, it's prone to carbon buildup, requiring periodic fuel injector cleaning. Multi-point injection, though slower in acceleration, is simpler to maintain and more stable on long trips, especially with quicker starts in winter. Overall, if you prioritize performance and fuel efficiency, direct injection is a great choice. But if you're on a tight budget or often drive in complex road conditions, multi-point injection is more worry-free. Many new cars now use direct injection combined with turbocharging, which truly enhances the driving experience.
