Digijet - Digifant

[Bernd Felsche]

Jens Knickmeyer tapped away at the keyboard with:

> 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

After 1987 in Europe. There's a 1988 Digifant ex-UK car cruising
around town. It's Digifant because I've swapped it into my car to
try to isolate a problem... the 1988 model was a "leaded" car, so
had no lambda.

> 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

As well as throttle-bypass air control.

> - OBD which implements the Volkswagen diagnosis protocol based upon ISO-9141

Only on the later versions and with California models. The FH suffix
ones, used for engines rated from 90 to 107 bhp don't support any
diagnostics.

> - MAF or MAP sytems using the same hardware design
> - cylinder selective knock control (only used with supercharged engines)

Cylinder-selective knock control is available on all Digifants, not
just the supercharged ones.  This is documented in several SAE
papers presented by Volkswagen staff in the late 1980's. The
supercharged ones had boost control under persistent knock.

> 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).

-- 
 /"\  Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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