What is Direct Fuel Injection?

by MOU YONG HONG on December 01, 2021

With the development of the economy, the penetration rate of the vehicle volume is getting higher and higher. It is worth mentioning that the direct injection technology is gradually popularized in more mainstream vehicles, and there may be inherent failures that we need to pay attention to.

What is direct fuel injection?

Direct fuel injection is a technology that delivers fuel directly to the injectors in the cylinders of internal combustion engines. The ability to deliver fuel directly to the cylinders can reduce emissions, lower the temperature of the cylinder head, provide more power and improve fuel economy.

How Direct Fuel Injection Works

This technology is an in-cylinder direct-injection technology developed to improve the lack of fuel supply of traditional gasoline engines. Advanced direct injection gasoline engines use fuel supply technology similar to diesel engines and provide the required 100bar through a piston pump. The above pressure supplies gasoline to the electromagnetic injector located in the cylinder. Then the computer controls the injector to inject fuel directly into the combustion chamber at the most appropriate time. The accuracy of the control is close to milliseconds. The key is to consider the installation of the injector, and a certain space must be left in the upper part of the cylinder. Since the spark plug and multiple valves have been arranged on the top of the cylinder, it is already quite compact, so it is arranged on the side close to the intake valve. Due to the addition of the ejector, the design and manufacturing requirements are quite high. If the layout is unreasonable and the manufacturing accuracy is not up to the requirements, it will lead to insufficient rigidity and even air leakage, which is not worth the loss. In addition, FSI engines have relatively high requirements for fuel quality. The current domestic oil conditions may be difficult to meet the requirements of FSI engines. Therefore, some imported engines equipped with FSI have become unacceptable. This leads to a decrease in the life of the engine. (For example, Honda engine, its naturally aspirated engine, I have seen the most maintenance record. This owner ran for 40,000 kilometers without maintenance. When he entered the shop, the oil was discharged, but it was less than half of the engine. The problem is the same. For Honda's direct-injection engine, even if it uses the best engine oil, it does not exceed 20,000 kilometers. Generally, it will turn on the oil lamp at about 15,000. The technology is still lacking).

Advantages of direct fuel injection

The advantages of the in-cylinder direct-injection gasoline engine are low fuel consumption and high power per liter.

The air-fuel ratio reaches 40:1 (the air-fuel ratio of a general gasoline engine is 14.7:1), which is what people call "lean burn".

The top half of the piston in the machine is spherical, and the other half is the wall surface. After the air rushes in from the valve, a swirling motion is formed under the compression of the piston. When the compression stroke is about to end, the fuel injection nozzle at the top of the combustion chamber starts to inject oil. Gasoline and air form a mixture under the action of vortex motion. This rapidly rotating mixture is divided into layers, and the closer it is to the spark plug, the denser it is, and it is easy to ignite and do work.

The compression ratio is as high as 12, and the power and torque are increased by 10% compared with the general engine of the same displacement.

The biggest advantage of the fuel supply system using an in-cylinder direct-injection design is that the fuel is directly injected into the combustion chamber at very high pressure. Therefore, except for the structure and position of the fuel injector, it is different from the traditional fuel supply system. And the mixing efficiency is also more excellent. In addition to the recent advances in the control technology of various electronic systems on the car, the computer has become more accurate in the interpretation and control of the intake air volume and fuel injection timing. Therefore, with the upper cylinder direct injection technology, the combustion efficiency of the engine is greatly improved. In addition to the engine being able to generate more power, it also has a positive effect on environmental protection and energy-saving.

Disadvantages of direct fuel injection

But the in-cylinder direct injection technology is not invincible, because, from an economic point of view, the use of an in-cylinder direct injection fuel supply system must cost more in the research and development process, and for car owners, it needs to replace the spark plug more frequently than traditional EFI vehicles. And other parts.

Higher fuel quality requirements require the use of higher-grade fuel, which virtually increases the cost of car owners.

In-cylinder direct injection engines are more likely to produce carbon deposits than traditional electronic injection engines, and car owners need to use expensive special additives for direct injection engines to solve the problem of carbon deposits.

Many of these emissions innovations sound good in theory and in writing, but after thousands of miles, the maintenance of these high-tech engines has decreased. If not properly maintained, these mechanisms may ironically hinder the functions they are designed to provide-fuel efficiency, power, and lower emissions. If you have any questions about the maintenance of direct injection engines, please feel free to contact us via VEP engine parts We provide services for all brands and models of direct injection vehicles and follow the recommended service intervals of each manufacturer.


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