Motronic

Motronic is the trade name given to a range of digital engine control units developed by Robert Bosch GmbH (commonly known as Bosch) which combined control of fuel injection and ignition in a single unit.

By controlling both major systems in a single unit, many aspects of the engine's characteristics (such as power, fuel economy, drivability, and emissions) can be improved.

These early Motronic systems integrated the spark timing element with then-existing Jetronic fuel injection technology.

It was originally developed and first used in the BMW 7 Series,[1] before being implemented on several Volvo[2] and Porsche[3] engines throughout the 1980s.

The components of the Motronic ML1.x systems for the most part remained unchanged during production, although there are some differences in certain situations.

Also present is adaptive circuitry, which adjusts for changes in an engine's characteristics over time.

The Motronic units have 2 injection outputs, and the injectors are arranged in 2 "banks" which fire once every two engine revolutions.

During start-up (below 600 rpm), or if there is no signal from the cylinder ID sensor, all injectors are fired simultaneously once per engine revolution.

[5] In BMW vehicles, this Motronic version did not have a cylinder ID and as a result, both banks of injectors fired at once.

(Modified successor of C20NE engine) Major change to the Motronic 1.5.2 was the use of DIS ignition system, knock sensor and EGR valve.

The ML 2.1 system integrates an advanced engine management with 2 knock sensors, provision for adaptive fuel & timing adjustment, purge canister control, precision sequential fuel control and diagnostics (pre OBD-1).

Fuel enrichment during cold-start is achieved by altering the timing of the main injectors based on engine temperature.

The idle speed is also fully controlled by the digital Motronic unit, including fast-idle during warm-up.

Updated variants ML 2.10.1 through 2.5 add MAF Mass Air Flow sensor logic and direct fire ignition coils per cylinder.

The ECU used one crank sensor to count the teeth on the starter ring for its RPM signal, and the other read a pin on the back of the flywheel for TDC reference.

The 3.6 V8 version had a distributor-based ignition system and was upgraded around the same time to coil on plug as its 20V turbo counterpart in 1992–1993.

[6] Motronic 3.7 is used in the Alfa Romeo V6 engine in the later 12 valve 3.0L variants, replacing the L-Jetronic.

The idle speed is also fully controlled by the Motronic unit, including fast-idle during warm-up (therefore no thermo-time switch is required).

The injectors are opened once for every revolution of the engine, injecting half the required fuel each time.

Features included OBD I diagnostics, dual knock sensors and a lot more.

For the 1996 model year OBD II diagnostics were introduced on some cars while M4.3 was beginning to be phased out.

OBD II was standard on all cars fitted with this system albeit the necessary protocols were not integrated for all markets.

The system was used for the five- and six-cylinder modular engined cars and was used on turbocharged and naturally aspirated models.

Compared to 1.7, Motronic 5.2 has OBD-II capability and uses a hot-wire MAF sensor in place of the flapper-door AFM.

Unlike the Motronic system in BMW sedans, that uses a chassis accelerometer to differentiate between misfires and rough road, the Land Rover version used signal from ABS control unit to detect rough road conditions.