What is the difference between multi-point fuel injection and direct fuel injection?
3 Answers
The difference between multi-point fuel injection and direct fuel injection lies in the injection method: the injectors of multi-point fuel injection are installed on the intake manifold, where fuel and air begin to mix in the manifold before entering the cylinder; direct fuel injection can directly inject fuel into the cylinder. Direct fuel injection involves installing the injector inside the combustion chamber, directly injecting gasoline into the cylinder combustion chamber, where air enters through the intake valve and mixes with the gasoline before being ignited to perform work. Multi-point fuel injection is a process in gasoline engines where the fuel injection occurs in the intake manifold, with control commands issued by the control program according to specific timing and executed through electronic fuel injectors.
I've driven both multi-point fuel injection and direct injection cars, and the experience is quite profound. Multi-point fuel injection is an older technology where the fuel injectors are located on the engine's intake manifold. Gasoline is first sprayed into the intake pipe to mix with air before entering the cylinder for combustion. The advantages are that it's cheaper, more durable, provides stable driving, and is simpler to maintain. The downside is slightly higher fuel consumption and slower power response. Direct injection is the newer approach, with injectors extending directly into the cylinder. Gasoline is sprayed in and burns immediately, making it much more efficient, with quicker acceleration and better fuel economy. However, a new issue arises: carbon buildup on the intake valves, requiring cleaning every couple of years, which increases maintenance costs. My friend's direct injection car has significantly lower daily fuel consumption, but each cleaning costs several hundred dollars and takes time. I think the choice depends on driving habits: multi-point injection is more worry-free for short city trips, while direct injection is more cost-effective for long highway drives.
After repairing cars for so many years, I've encountered many car owners asking about fuel injection systems. Multi-point fuel injection has a simpler structure, with the injectors fixed at the engine intake where gasoline is sprayed and mixed with air, resulting in fewer issues. Usually, replacing an injector costs just a few dozen bucks. Direct injection is different; the injectors are placed inside the cylinders, offering precise fuel control, delivering strong power with low fuel consumption. However, intake valve carbon buildup is a common issue with direct injection, especially when driving in the city at low RPMs, where carbon accumulates quickly. Cleaning it is troublesome, requiring disassembly, and it can't be done for less than a few hundred bucks. Among my regular customers, direct injection car owners report carbon buildup issues every one or two years. Nowadays, new cars prefer using direct injection plus turbocharging for better fuel efficiency, but it's essential to pay extra attention to regular maintenance and use additives to prevent clogging.
