Siemens vs Bosch. Part 1

 

Since long ago, BMW uses engine management systems of both brands – Siemens and Bosch. What concerns petrol engines (4/6 cylinder versions), initially Jetronic/Motronic solutions from Bosch were used, then was a period of Siemens MS41/42/43, then MSV70/80/MSD80/81/87 were used in 6-cylinder N series engines. Bosch returns with MEV9/ME9.2 4 in 4-cylinder engines and MEVD17.2/17.4 – in 6-cylinder engines.

 

In this entry – short comparison, performing diagnostics with INPA.

 

It should be remarked, that Bosch engine management systems are more simple, but, unfortunately, it doesn’t means, that diagnostics is more simple. On the contrary – limited possibilities of self-diagnostics and also the limited amount of live data makes the repair of these systems more complicated in case of more serious damages.

 

As a sample: MEV9/ME9.2 engine management system, which was installed, for example, on N46 engines.

 

Fuel adaptation menu.

If the engine uses 1 + 1 probes [1 piece wideband + 1 piece control probe], choose F5 [in analog data module];

If the engine uses 2 +2 probes [2 pieces wideband + 2 pieces control probes], choose Shift + F5 [in analog data module].

 

Data, available in this menu, are very limited.

Are not displayed:

a) data of heating and status (pre-heating/heating and similar) of probes;

b) values of wide-band Lambda probes;

c) dynamic resistances of Nernst cells are not visible – they would allow evaluating the chemical efficiency of probes.

First line: voltages of wide-band probes. If Lambda =1.00, U=1.50V. It look’s that for data analysis Bosch LSU 4.9 Datasheet, for a solution with K=17, can be used.

Control conditions: in overrun mode, U has to be around 4.00V.

 

Second line: voltages of control probes.

Voltage for cold probes (reference voltage source) 0.50V.

 

Third line: integrators.

These data are not displayed in percents, what would be more convenient, but are shown ar multiplier with reference value 1.00.

 

Fourth line: offset type adaptations.

Data are displayed in absolute values, reference 0.

 

Fifth line: multiplicative adaptations.

These data are not displayed in percents, what would be more convenient, but are shown ar multiplier with reference value 1.00.

 

Unlike Siemens concept, Bosch engine management systems are more based on fuel/ignition maps and LTFT, integrators are working significantly slower.

 

VANOS

VANOS (unlike the Siemens concept, where VANOS is active above 800 .. 1000 RPM) is active also in idle, which means, that this knot can be the cause of uneven idle. Good news – PWM actuator values can be seen in VANOS menu. Normal jittering is +/-5%. In case of increased jittering – obviously, the solenoid(s) has to be cleaned or replaced.

 

Misfire counters.

MEV9/ME9.2 don’t report misfire counters in OBD mode 6. MEVD17/2/17.4 – reports.

 

Deleting of adaptations.

Deleting of adaptations is much more simple than in MSV/MSD concepts.

As can be seen, adaptations are divided into 6 groups, and are not very creative. It is not quite clear, how to delete throttle, VANOS, Valvetronic, flywheel etc. adaptation (of course, if they really are existing).

 

It is interesting, that detonation/knock sensor values of each cylinder are separately highlighted (deleting of this adaptation also is possible):

Two menus are reserved for FASTA data, which are much more convenient to read, using ISTA, because abbreviations, used in INPA, are not very informative: