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Author: Weibo
Yesterday, some enthusiasts in the group discussed the operation of the fuel injection system, particularly when fuel cut-off during deceleration begins and which sensor controls it. Some said it’s controlled by the rapid return of the throttle, while others claimed it’s controlled by the throttle position sensor. It’s worth noting that the throttle control and throttle position are essentially the same thing, and whether fuel is cut off and the timing of that cut-off cannot be dictated by a single sensor’s signal. The ECU must comprehensively assess signals from various sensors.
While the discussions among enthusiasts in the group indicate a good atmosphere for learning about fuel injection, they also highlight a significant gap in knowledge. Today, we will detail the precise corrections made by the fuel injection system under six major operating conditions. This is the seventh installment in our series on fuel injection knowledge; those interested can go back and read the previous articles.
The electronic fuel injection system (as shown in the above image) has several advantages discussed in previous chapters, but the most critical element is how to inject the right amount of fuel at the right time to keep the engine running continuously. The fuel injection amount control in a typical electronic fuel injection system is expressed as: 〖Injection Duration Signal = Basic Injection Duration × Injection Correction Factor + Voltage Correction Value〗. The basic injection duration varies with air flow and engine speed. The fuel injection control system has several types of corrections for the injector:
(1) Fuel Quantity Correction After Start
During a cold start, the cylinder temperature is low, and fuel vaporization is poor, necessitating an increase in the injection amount.
(2) Fuel Quantity Correction During Warm-Up
After a successful cold start, the cylinder temperature remains low. To quickly bring the engine to operational status, a richer mixture is required.
(3) Intake Temperature Correction
As engine speed increases, the intake temperature rises, and air density decreases. Without correction, the mixture will become rich. Therefore, corrections for intake temperature are necessary.
(4) Power Correction
When a motorcycle is traveling at high speed, the engine operates under a heavy load condition, necessitating a richer mixture to achieve greater power. The ECU will assess the load condition based on the throttle position or intake volume and adjust the injection amount accordingly.
(5) Fuel Quantity Correction During Deceleration
During deceleration, the vacuum in the intake manifold increases, causing the mixture to become rich, which requires a reduction in the fuel quantity.
(6) Fuel Quantity Correction During Acceleration
During acceleration, the throttle opens rapidly, increasing the air volume while decreasing the vacuum in the engine’s intake manifold, slowing down the fuel evaporation rate, leading to a leaner mixture. However, the engine requires a richer mixture to generate greater power, thus necessitating an increase in fuel quantity.
The ECU will determine the acceleration condition based on the rate of change of the throttle position or air flow, as well as engine speed, and calculate the acceleration fuel correction factor. In cases of rapid acceleration, the ECU will instruct asynchronous injection to supplement the fuel supply.
This series of articles on fuel injection aims to popularize knowledge of fuel injection and basic maintenance methods, with explanations progressing from simple to complex in chapters and sections. Please continue to follow us; to be continued!
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