Emission Modules/Control Units
The Digifant Engine Management System (North American Vehicles Only) is an electronic fuel injection system designed by Volkswagen A.G. in cooperation with Robert Bosch GmbH. more...
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Digifant is the outgrowth of the Digi-jet Fuel Injection system first used on water-cooled Type 2 based volkswagen vehicles.
History
Digifant was introduced in 1986 on the 2.1L Vanagon Engine. This system combined digital fuel control as used in the earlier Digi-Jet systems with a new digital ignition system. Digifant as used in Golf and Jetta models simplified several functions and added knock sensor control to the ignition system. Other versions of Digifant appeared on the Fox, Corrado, Eurovan as well as later production versions of the rear engined VW Beetle, sold only in Mexico.
Features
Fuel injection control is digital electronic. It is based on the measurement engine load (this signal is provided by the Air Flow Sensor), and on engine speed (Signal provided by the hall sender in the distributor). These primary signals are compared to a map, or table of values, stored in the Engine Control Module (ECM) memory.
The amount of fuel is controlled by the injector (duration). This value is taken from a program in the ECM that has 16 points for load and 16 points for speed. These 256 primary values are then modified by coolant temperature, intake air temperature, oxygen content of the exhaust, battery voltage and throttle position to provide 65,000 possible injector duration points.
Digifant is unlike the earlier CIS and CIS-E fuel injection systems that it replaced in that fuel injectors are mounted on a common fuel rail. CIS fuel injection systems used mechanical fuel injectors. The fuel injectors are wired in parallel, and are supplied with Constant System Voltage. The ECM switches the Ground on and off to control duration. All injectors operate at the same time each crankshaft revolution; two complete revolutions being needed for each cylinder to receive the correct amount of fuel for each combustion cycle.
Ignition control is also digital electronic. The sensors that supply the engine load and engine speed signals for injector duration provide information about the basic ignition timing point. The signal sent to the Hall control unit is derived from a program in the ECM that is similar to the injector duration program.
There are 16 points available for load and 16 points for speed. The resulting 256 single operational points are modified by coolant temperature signals and cylinder selective knock control to achieve the optimal ignition point.
Knock control is used to allow the ignition timing to continually approach the point of detonation. This is the point where the engine will produce the most power, as well as the highest efficiency.
Read more at Wikipedia.org
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