Automobile Engine Injection and Ignition Using the Motorola MPC555 Microcontroller
Rick Wagoner
Information Education and Technology 645, Section 001
Professor Dr. Yudi Gondokaryono
May 2, 2006
Automobile Engine Injection and Ignition
Introduction
Automobile engines and powertrains have become a major growth area for microcontroller use. This growth is also expected to continue. As many new regulations concerning the exhaust emissions and fuel efficiency must be met then more and more microcontrollers on automobiles will be required. One area that currently makes use of a microcontroller is that of fuel injection and engine ignition.
These two areas can both be controlled in a manner that can greatly increase fuel efficiency, lower exhaust emissions, and also improve engine power performance. Let’s begin by looking at fuel injection. Injecting the proper amount of fuel into the engine at the proper time allows the engine to operate a peak performance levels. This process can be accomplished without the use of a microcontroller. However, due to the many factors affecting what constitutes the proper amount and proper time makes the use of a microcontroller much more appealing. The microcontroller can gather the readings from sensors connected to many components on the engine to perform calculations determining the proper amount and proper time for the injection process to occur. The higher the temperature on the engine the better the fuel burns. As the fuel burns more efficiently less fuel is required to generate the same amount of energy. Having a temperature sensor on the motor providing input to the microcontroller allows for adjustment of the amount of fuel being injected into the motor to provide the same amount of engine output energy. These calculations are quite complex and thus would take some time for a person to perform. The microcontroller can gather the data, perform the calculations, and make the necessary adjustments in a fraction of a second. The
gathering and adjustment process can thus be performed many times per second allow for continuous levels of higher engine performance.
Likewise, the ignition process can also be controlled in a similar process. Ignition needs to occur at a time that will allow the engine to provide the most energy for use. If the ignition is ‘fired’ exactly when the piston is at its highest point then energy will be lost. The amount of time that it takes for the ignition to fire and then travel to the piston allows the piston to move downward. Then when the fuel is ignited and the reaction takes place energy is not used to its full potential because the piston can not gain a full
‘stroke’ from the reaction but rather is moved what distance is available thus operating at less than peak efficiency. However, if the ignition process is started slightly before the piston reaches its uppermost position the engine energy is thus used to its full potential. Again in this scenario a measurement must be taken and a calculation must be performed and then an adjustment made. The quicker this can be down the more efficient the engine will operate.
For both injection and ignition there are many factors that will affect the outcome of the calculations required to adjust the engine into peak efficiency. As was discussed with the injection process, engine temperature plays a key role and engine speed greatly affects the ignition process. These factors are the key reason that a microcontroller is used instead of monitoring these elements manually. A person is simply incapable of keeping track of all of these factors and then also considering them in determining the proper adjustments to be made. This is why I will only assume a minor set of these factors for discussion in designing a basic microcontroller system to control both fuel injection and engine ignition.
