Porsche street cars first received computerized engine management for the 1980 model year. By today’s standards, the early version was elementary in comparison. This addition was obvious by the installation of an oxygen sensor to monitor oxygen content in the exhaust stream. This was Porsche’s approach to improve engine performance and tailpipe emissions in most operating conditions. In 1984 Porsche installed a full computerized engine management system named Digital Motor Electronics (DME) in the 911 Carrera. DME controlled not only the fuel injection but also the ignition system making it a complete package with one control unit for the entire engine management system.
A basic description of the computerized engine management system is a control unit (computer), also known by some as the brain, which receives data from sensors on the engine that are monitoring its operation. These sensors monitor engine temperature, RPM or speed, throttle position, intake air with an air flow or air mass meter and an oxygen sensor for exhaust oxygen content just to name a few. By monitoring these various engine operating inputs, the control unit does the math and computes the proper output delivery for the fuel injectors and ignition timing also dependent on the driver’s request.
The Control unit has the ability to make changes to adjust the amount of fuel going into the engine. An example might be if the control unit sees that the engine is running leaner than normal i.e. excessive amounts of oxygen in the exhaust stream, the computer will adjust accordingly and the engine will run richer on fuel.
In this day of computerized automotive electronics, most cars can have up to 100 or more control units. The modern automobile is a huge rolling laptop with a computer for almost every driver input. Due to the sensitivity of these control units extreme care should be taken when maintenance, diagnosis and repairs are performed.
Tony Callas & Tom Prine