What is the difference between direct injection and electronic fuel injection in cars?
2 Answers
The differences between direct injection and electronic fuel injection in cars are as follows: Different fuel injection methods: Electronic fuel injection sprays fuel into the engine intake manifold, while direct injection sprays fuel directly into the engine cylinder. Different installation positions of the fuel injector: In multi-point electronic fuel injection, the fuel injector is installed at the end of the intake manifold, and the fuel spray is directed into the intake ports of each cylinder; the air-fuel mixture is formed outside the cylinder. In direct injection, the fuel injector is installed on the cylinder head, and fuel is sprayed directly into the cylinder; the air-fuel mixture is formed inside the cylinder. Different fuel injection pressures: Multi-point electronic fuel injection operates at pressures of 2.5bar to 4bar, while direct injection operates at pressures of 40bar to 400bar. Different fuel supply system compositions: Multi-point electronic fuel injection does not have a high-pressure fuel pump, whereas direct injection includes a high-pressure fuel pump. Different fuel injection start angles and durations: Due to the lower injection pressure in multi-point electronic fuel injection, the injection duration is longer under high load, and the next injection cycle may need to start after the intake valve closes. However, direct injection occurs after the intake valve opens. Injection can happen during both the intake stroke and the compression stroke. Because direct injection sprays fuel into the cylinder, it can lower the cylinder temperature during compression, helping to dissipate heat from the piston and cylinder liner, thereby reducing the engine's tendency to knock. As a result, direct injection engines can achieve a higher compression ratio, improving thermal efficiency.
The main difference between direct injection and electronic fuel injection lies in the fuel injection position. The direct injection system sprays fuel directly into the cylinder, and the high-pressure fuel pump makes the fuel mist finer, resulting in more complete combustion, stronger power, and better fuel efficiency. My older car used electronic fuel injection, where fuel is injected into the intake manifold, making control simpler but response slower. After switching to a direct injection car, the acceleration became much faster, and fuel consumption dropped by about 15%. However, if not cleaned regularly, carbon deposits can accumulate over time, affecting engine performance. It's recommended to use direct injection more often for city driving, as the difference is even more noticeable on highways. Don't forget to perform regular maintenance to clean carbon deposits.
