Digijet - Digifant

[Jens Knickmeyer]

Morton,

Digijet was developped by Volkswagen because they needed an ECU which could
handle lambda control. Development started at the beginning of the 80s because at that
time it became clear that in Europe the cat. converters were soon to be introduced and
VW wanted a reliable system which couzld be easily adapted to several cars. It is basically a 
Bosch L-Jetronic, only the ECU was designed by VW because at that times Bosch had only
analog ECUs and VW wanted to use a digital one. So, all peripheral components as
fuel pumps, fuel filters, fuel rail, injectors and sensors are L-Jet parts. Some people call 
the Digijet "L2-Jetronic". Digijet handles only fuel injection, there is no ignition management 
(this was done by a seperate ECU called "Dignition"). Digijet has always been a MAF system.
The Digijet lying next to my keyboard is based on a 8049 controller. Firmware is kept in a 
4k(!)-EPROM. There is no OBD or any other sophisticated features as for example idle revs 
stabilisation. Digijet is very simple and therefore in Germany a good choice for tuning.

Digifant was developped by Volkswagen, too. In contrast to Digijet, Digifant is a complete
motronic system which implements injection an ignition management. The system came out
in the early '90s (at least in Germany). It was available as a MAF or MAP system. The MAP
systems were used in the cars which used the Volkswagen "G-Lader", a mechanical supercharger
(In America, there are even non-supercharged cars equipped with MAP Digifants). The MAF
systems were used in non-supercharged European cars as the Golf, Passat, Corrado.
Digifant was re-designed several times. Early ECUs have a 8051 for ignition management and
a 6909 for injection management. Later, a single 68HC11 was used for both tasks, whereas
the ECU still contained two boards - an analog and a digital board (the '90 Corrado used such 
an ECU). My '92 Polo-G40 has a Digifant with only one board, and AFAIK, this is the last
evolution of Digifant.

Features of Digifant are:
- idle rev. stabilisation using spark timing
- OBD which implements the Volkswagen diagnosis protocol based upon ISO-9141
- MAF or MAP sytems using the same hardware design
- cylinder selective knock control (only used with supercharged engines)

Coding a Digifant system is possible but takes a lot of time because the diagnosis protocol
takes approx. 70% of all code, and it is a hard job to identify which parts of code belong to
OBD and which belong to engine control.


If you have specific questions (e.g. concerning the NZ engines and their engine control) feel free 
to ask me via email (that way we don't bore the other 95% of the list members which are interested
in American/Australian engines).

Regards,

Jens Knickmeyer
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