What is the difference between electronic fuel injection and direct injection in cars?
3 Answers
The difference between electronic fuel injection engines and direct injection engines lies in the way throttle opening is controlled. Direct injection engines control fuel injection based on engine speed, where the throttle opening is manually adjusted via a throttle knob and the power mode switch, resulting in a relatively simple overall structure. On the other hand, electronic fuel injection engines detect various signals such as throttle opening rotation angle, power mode switch, engine speed, fuel pump pressure speed, pilot control valves for each operation valve, excavator working mode, as well as water temperature and oil temperature signals. The engine control unit (ECU) then calculates and controls the fuel injection based on the driver's operational intent.
I've been driving a taxi for almost twenty years, so I know the difference between port injection and direct injection like the back of my hand. Port injection sprays gasoline into the intake manifold, mixing it with air before it enters the cylinder. Direct injection is more advanced—it sprays fuel directly into the cylinder for combustion. Direct injection delivers more power and better fuel efficiency. My new direct-injection taxi saves half a liter per 100 kilometers. However, direct injection cars are more expensive to maintain, as the fuel injectors are prone to carbon buildup and require frequent cleaning. Port injection cars are much more hassle-free—they run fine on 92-octane gas and are cheaper to repair. In my opinion, direct injection is better for long-distance driving, while port injection is more practical for city commuting.
Last time I helped my son choose a car, I finally understood this. EFI (Electronic Fuel Injection) cars are like old-fashioned teapots, where gasoline slowly boils in the intake manifold; GDI (Gasoline Direct Injection) cars are like pressure cookers, directly injecting fuel into the cylinders. My son insisted on a GDI turbocharged car, saying it accelerates faster with strong back-pushing force, but the maintenance is really troublesome. The 4S shop said GDI cars need regular carbon deposit cleaning, otherwise the fault light will come on. EFI cars don't have this problem—our old Camry hasn't had its fuel injectors cleaned in ten years. The key is driving habits: young people who enjoy sporty driving are suited for GDI, while us middle-aged and elderly folks who just shuttle kids around are better off with EFI—more reliable and cost-effective.
