Introduction | 3B Description | ABY Changes | Schematics | Boost Control | Diagnostics

Bosch Motronic Info

An Introduction to the Bosch Motronic ECU

The Bosch Motronic system is one of the most advanced engine management computers ever fitted to a production car. It has been successfully used by a wide variety of European car manufacturers in many different guises and configurations. Audi have a long history with using Bosch ignition & injection components so it is no surprise that their flagship Motronic system was fitted to Audi's top line of turbocharged engines.

The RR engined 20V UR-quattro made good use of the Motronic system for the model years of 1990 and 1991. The 3B engine first appeared on the 200 Turbo Quattro mid way through the 1989 model year. This engine was employed on the S2 Coupe for model years 1991 and 1992. The Motronic implementation on the S2 is responsible for the following main functions :

1. Electronic Ignition Timing

2. Sequential Fuel Injection Timing

3. Turbocharger boost control

4. Emission Control Systems

5. On board Diagnostics (OBD)

The Bosch Motronic ECU is an adaptive control system that is capable of making dynamic adjustment to the engine's operating parameters in response to changing operating conditions e.g fuel quality. 

There are some differences between the Motronic system, and it's associated components on the 3B and ABY engines. This section of the site aims to firstly describe the ECU operation on the 3B engine before indicating the changes that were made for the ABY engine. It is worth noting that the ABY engine is just about identical (from an ECU point of view) to the later AAN engines used on the UrS4/S6.