Digifant
Digifant is the name for an engine control unit series of the Volkswagen Group. The made-up word Digifant is made up of “digital injection” and “white elephant”. The Digifant is a further development of the Digijet and the ignition system (Dignition) and combines both individual systems into one engine control unit. The aim of this summary was to obtain the lowest possible emissions and economical consumption with optimal performance. It has been continuously developed, with additional functions being added or changed depending on the engine type and year of manufacture. The Digifant was finally replaced by the successor system Simos .
construction
The Digifant is an electronically controlled injection system with programmed maps for injection time and ignition point. It has overrun fuel cut-off, lambda control, cold start, warm-up and full load enrichment. Depending on the type, the injection valves are activated simultaneously or sequentially and inject the fuel into the intake manifold in front of the intake valves. The ignition point is determined electronically in all Digifant variants. Most Digifant variants have electronic idle control with the aid of an idle actuator and knock detection with one or two knock sensors.
Mixture correction
Starter detection
The control unit recognizes the start of the engine. The switching of the fuel pump relay is ensured by the voltage signal in the event of a voltage drop in the battery. Digifant versions with sequential injection require two crankshaft revolutions when starting to detect the TDC of the first cylinder and only then cycle the injection valves.
Cold start
The injection valves are opened longer by the control unit in order to enrich the mixture. The opening time decreases as the cooling water temperature rises. The lambda control is deactivated. The idle is increased by the idle actuator.
Warm-up phase
In the warm-up phase, the idling is stabilized by the idling actuator. The lambda control is switched on from a certain cooling water temperature.
Load changes
The throttle valve switch and / or the throttle valve potentiometer send the idling or full load information to the control unit, which changes the injection time depending on the position of the air flow meter or the vacuum or pressure sensor in the control unit.
Change in intake air temperature
Detection via the intake air temperature resistance. The control unit responds by lengthening or shortening the injection time.
Speed limitation
The control unit receives the speed information from the Hall sender in the distributor or from the Hall sender on the crankshaft and reduces the injection time between 6400 min −1 and 6500 min −1 . The water boxer engines this is already happening at 5400 min -1 .
Fuel cut-off
Detection via speed and throttle valve position; the control device stops the injection engine at operating temperature, wherein the accelerator pedal released and above 1500 min -1 .
Full load
Detection via speed and throttle valve position; the control unit also increases the opening time of the injection valves.
Lambda control
A lambda probe detects a rich or lean mixture, and the injection time is changed accordingly.
Ignition timing
The engine control unit uses the cooling water temperature, engine speed, load status and, if available, the knock sensor (s) to adjust the ignition timing. The idling is also stabilized via the ignition point.
variants
The Digifant variants are very different. Due to constant further development, new functions were added or changed. The first Digifant variants had a baffle flap air flow meter, an additional air slide, a throttle flap switch and injected fuel simultaneously. There were also Digifant variants with or without lambda control, which found their way into all variants a short time later. Knock detection with one or two knock sensors and idling control via an idling actuator were later integrated. In a smooth transition, the air flow meter for airflow flaps was replaced by a vacuum or pressure transmitter in the control unit and the throttle valve switch by a throttle valve potentiometer with or without an idle switch. The newer Digifant variants inject sequentially, are adaptive, so that the CO value and the idle speed no longer have to be set, and they cushion load shocks via the idle actuator. They also have various signal inputs and outputs for engine speed, speed and consumption information, idling speed increase, automatic transmission and immobilizers. Almost all Digifant variants can be diagnosed. Some newer ones have to be relearned when changing the throttle valve potentiometer or the idle switch (a so-called throttle valve basic setting). The Digifant was installed in almost all models of the Volkswagen Group from 1985 to 2005, but also in the Group's subsidiaries Audi and Seat.
Overview of the Digifant variants
| model | Displacement | design type | Cyl. | kW / PS | MKB | construction time |
|---|---|---|---|---|---|---|
| 2.1 l | 2081 cc | WBX | 4th | 70/95 | MV | 1985-1992 |
| 2.1 l | 2081 cc | WBX | 4th | 64/87 | SR | 1986-1992 |
| 1.3 l | 1272 cc | line | 4th | 85/115 | PY | 1986-1994 |
| 1.3 l | 1272 cc | line | 4th | 55/75 | 3F | 1990-1994 |
| 1.8 l | 1781 cc | line | 4th | 77/105 | RV | 1987-1991 |
| 1.8 l | 1781 cc | line | 4th | 79/107 | PF | 1987-1991 |
| 1.8 l | 1781 cc | line | 4th | 82/112 | PB | 1987-1991 |
| 1.8 l | 1781 cc | line | 4th | 72/98 | 2H | 1988-1993 |
| 1.8 l | 1781 cc | line | 4th | 72/98 | 1P | 1988-1991 |
| 1.8 l | 1763 cc | line | 4th | 118/160 | 1H | 1988-1989 |
| 1.8 l | 1781 cc | line | 4th | 118/160 | PG | 1988-1993 |
| 2.1 l | 2081 cc | WBX | 4th | 68/92 | SS | 1989-1992 |
| 1.8 l | 1781 cc | line | 4th | 154/210 | 3G | 1989 |
| 2.0 l | 1984 cc | line | 4th | 85/115 | 2E | 1990-1996 |
| 2.5 l | 2461 cc | line | 5 | 81/110 | AAF | 1990-1993 |
| 2.0 l | 1968 cc | line | 4th | 62/84 | AAC | 1990-2003 |
| 2.0 l | 1984 cc | line | 4th | 85/115 | ABK | 1991-1998 |
| 2.0 l | 1984 cc | line | 4th | 110/150 | ABF | 1992-1999 |
| 1.6 l | 1584 cc | boxer | 4th | 34/46 | ACD | 1992-2003 |
| 1.8 l | 1781 cc | line | 4th | 66/90 | ADD | 1993-2005 |
| 2.5 l | 2461 cc | line | 5 | 81/110 | ACU | 1993-1996 |
| 1.8 l | 1781 cc | line | 4th | 95/129 | ADL | 1994-1996 |