Idle air control
A block diagram of a simplified idle speed control system is shown in Fig. b. Idle speed is detected by the RPM sensor, and the speed is adjusted to maintain…
Idle speed control
Idle speed control is used by some manufacturers to prevent engine stall during idle. The goal is to allow the engine to idle at as low an RPM as possible,…
Deceleration leaning
During periods of light engine load and high RPM such as during coasting or hard deceleration, the engine operates with a very lean air/fuel ratio to reduce excess emissions of…
Closed-loop control
Perhaps the most important adjustment to the fuel injector pulse duration comes when the control is in the closed-loop mode. In the open-loop mode the accuracy of the fuel delivery…
Open-loop control
For a warmed-up engine, the controller will operate in an open loop if the closed-loop mode is not available for any reason. For example, the engine may be warmed sufficiently…
Engine warm-up
While the engine is warming up, an enriched air/fuel ratio is still needed to keep it running smoothly, but the required air/fuel ratio changes as the temperature increases. Therefore, the…
Engine crank
While the engine is being cranked, the fuel control system must provide an intake air/fuel ratio of anywhere from 2:1 to 12:1, depending on engine temperature. The correct [A/F]d is…
Control modes for fuel control
The engine control system is responsible for controlling fuel and ignition for all possible engine operating conditions. However, there are a number of distinct categories of engine operation, each of…
Digital engine control features
The primary purpose of the electronic engine control system is to regulate the mixture (i.e., air–fuel), the ignition timing, and EGR. Virtually all major manufacturers of cars sold in the…
Digital engine control
A typical engine control system incorporates a microprocessor and is essentially a special-purpose computer (or microcontroller). Electronic engine control has evolved from a relatively rudimentary fuel control system employing discrete…
