Motronic 3 ecu tuning

Motronic mapping

1. Background

Motronic is widely used vehicle Electronic Control Unit by Bosch.  Early model Bosch systems based on mechanical action for airflow measurement and fuel metering (k-Jetronic) .  Next gneration systems utilized "analog computer", that meanst no (re)programmable microcomputer but just analog components like op-amps, comparators etc.

In this article we only concider  digital ECUs (Motronic), by  digital we  mean that all input information is converted to digital format, then the information is processed and finally reconverted back to analog signal if needed. Digital ECU tuning  and mapping has followed the development of microchip industry over the last 20 years or so.  Microhip industry aims to produce higher  integration of  functionality, for example on chip peripherals like memories, AD/DA conververs, communication systems are now followed by user programmable gate arrays and even programmable analog modules for so called system on chip development.

From tuners perspective the big change took place when microcontroller started to have integrated (flash) memories, this happened around 1995.  Before that microcontroller memories (e.g. fuel and spark maps which are altered by tuner) were physically apart from the microcomputer, typical memory technology for ECUs at that time was EPROM (ErasableProgrammableReadOnlyMemory), programming this memory  requires a special device that applies correct voltage levels for chip pins  (address, data and control lines). Erasing EPROM is normally done by exposing memory to UV-radiation.  Low cost EPROM programmer can be bought e.g. or it can be  build from scracth.  Since then microcontrollers started to have electronically erasable (FLASH) memories onboard and programming is done normally by some system interface like JTAG or serial bus and it is common language that we say that ECU been flashed.

2. Tuning

Chipping meand normally mapping the engine (e.g. finding optimal fuel and spark maps ) or reprogramming the ecu control program with code that has been proven applicable othervise. First option requires comprehensive knowlegde of engine operation and special equipment like dynamometer and tools for air/fuel ratio and knock detection, just to name just few of them, also risk of engine damage is always present.

During the mapping engine is driven in dynamometer, the dynamometer is for "braking" the engine, meaning the engine is given certain load to work against and by measuring this load firstly engine torque  can be determined and secondly engine power can be calculated by multiplying the torque by engine speed. In case of ecu contains EPROM memory the mapping can be easier if so called EPROM emulator is deployed, this device looks like normal memory by ecus perspective but its data can be altered at all times, no EPROM disconnecting, erasing, programming and attaching cycle is needed. 

Even if memory content editing could be done by normal hex editor program, special type hex editor is normally used instead. Programs like TunerPro and Winols provide handy and efficient platform to select and edit memory blocks (maps) . These programs use ecu specific definition files which select sections of memory that contains maps and other values to be changed.

If new tune (new maps and other program changes) is readily at your disposal, only thing needed is just replacement of code in memory (via EPROM programming or by replacing whole memory chip).