The Difference Between Multi-Point Fuel Injection and Direct Injection

[OEmily]

Multi-point fuel injection is more economical in maintenance and more mature in technology compared to direct injection, but it is not as efficient in fuel consumption as direct injection, leading to increased fuel usage and unnecessary waste. On the other hand, direct injection offers more precise fuel delivery and better combustion, resulting in fuel savings and greater horsepower. Below is an introduction to direct injection and multi-point fuel injection: 1. Direct injection technology is a relatively new and advanced fuel injection method. 2. The advantages of direct injection include lower fuel consumption, higher power output, and a compression ratio of up to 12, with power and torque increasing by 10% compared to conventional engines of the same displacement. 3. The drawbacks of direct injection include more complex components, higher costs, and greater technical requirements, with the main challenge being the implementation of 'stratified combustion.' 4. The electronic fuel injection system in automotive engines generally consists of three main components: the fuel injection circuit, sensor group, and electronic control unit. 5. The advantages of multi-point fuel injection include simpler structure, lower requirements for injectors, and better performance in maintenance and reliability. 6. The disadvantages of multi-point fuel injection are that, while it improves the issue of uneven air-fuel mixture distribution found in single-point injection, it still falls short in achieving optimal fuel atomization and air-fuel mixture.

[RichardDella]

Over the years of repairing cars, I've observed that the most intuitive difference between multi-point fuel injection and direct fuel injection lies in the injector position. Multi-point injection sprays fuel into the intake manifold, where air and fuel mix before entering the cylinder. Direct injection, however, injects high-pressure fuel directly into the combustion chamber for more immediate mixing. Injection pressure is another major distinction—direct injection typically operates at much higher pressures, placing greater demands on the fuel pump. The control logic differs significantly too; direct injection allows for multiple injection events to optimize combustion and can work with stratified charge technology, though carbon buildup is noticeably worse than with multi-point injection. In actual driving, direct-injection vehicles offer quicker throttle response and better fuel economy, especially in today's common turbocharged direct-injection combinations. For maintenance, multi-point systems are simpler and easier to service, while direct-injection cars require higher fuel quality and face more complicated injector cleaning when clogged. Regarding technological trends, some new vehicles now employ dual injection systems to combine the advantages of both approaches.

[DeIsabel]

Last time I compared my uncle's old multi-point fuel injection car with my new direct injection car. The multi-point fuel injection car feels smooth in power delivery, with linear acceleration but average explosive power. The direct injection car gives an immediate push-back feeling when you step on the gas, especially noticeable when the turbo kicks in. In terms of fuel consumption, my car is significantly more fuel-efficient, but it requires 95-octane gasoline, while my uncle's car can run on 92. Regarding usage costs, the multi-point fuel injection engine is indeed more worry-free—it's been running for ten years without any engine vibration. The direct injection car has higher maintenance requirements; last time the 4S shop said my intake valves had carbon buildup that needed cleaning, and the mechanic mentioned this is a common issue with direct injection engines. Both technologies are still in use, each with its own characteristics.

[EverlyRose]

I've discussed these two technologies with experienced auto repair masters before. Multi-point fuel injection has a simple structure with injectors installed at the intake manifold position, featuring low cost and easy maintenance, which was commonly used in older car models. Direct injection extends the injector directly into the cylinder, with fuel injection pressure capable of exceeding 200 bar, resulting in excellent fuel atomization and naturally higher combustion efficiency. However, the high-pressure fuel pump and injectors require high precision, leading to correspondingly higher maintenance costs. Carbon deposit situations also differ; multi-point injection mainly requires throttle cleaning, while direct injection is particularly prone to carbon buildup on the back of the intake valves. With technological advancements, both have seen improvements nowadays, depending on whether you prioritize power and fuel efficiency or worry-free durability.