Bosch Torque Model

The Bosch ECU uses a different approach than other ECUs, where every aspect of the operation of the engine is mathematically modeled in the ECU.  This is complex with over 10,000 tables and 20,000 parameters.

Tuners familiar with the Bosch ECU may recognize some of the tables used in the ECU but caution must be advised.  A lot of information and advice on forums etc if for olded Bosch ECUs using ME7 or MED8 operating systems.   Honda using MED17, which is different from the earlier Boash ECUs ever if is uses the same tables.

The ECU torque model is that the ECU has a base maximum torque. The Bosch name is MDNORM.  For the Honda this is set to 600 Nm, but it is important to realize that this does not limit torque to 600 Nm.  Raising the value will actually lower the engine output unless every other torque table is adjusted.

The throttle tables are an Nm and are divided by the MDNORM to calculate a percentage torque, 0-100%.  Bosch refers to this percentage torque as load. If the throttle table has 150 Nm at a particular rpm and throttle position then the requested torque will be 150/600 = 25%.  The requested torque cannot be over 100%, nor less than 0%.  There is no point raising the torque in any of the throttle tables over the MDNORM value.

The percentage torque is then limited by the maximum torque table to make the requested percentage torque.

The ECU will adjust the requested percentage torque for accessory and other losses, and also add a torque reserve at low rpm, so typically the the adjusted torque request will be around 2 to 5% higher than the value from the throttle table divided by the base maximum torque.

From there the ECU uses the 'Nominal charge table (KFMIRL)' table to look up the air charge from the requested torque and rpm.  The air charge normally has a range of 0-250% (ignoring unobtainable areas of the table) but this can be expanded to 0-350% by using a modification.  If the KFMIRL table is altered it is critical that the KFMIOP table is altered as well - more about that below.

From the air charge the ECU will calculate the target manifold pressure.  Roughly 80% air charge is 100 kPa absolute manifold pressure, but the exact conversion varies as it considers ignition timing efficiency, lambda efficiency, cam timing efficiency, residual exhaust gases and other adjustments.

The ECU will operate the throttle and wastegate to achieve the target manifold pressure.  For target below atmospheric pressure it uses the throttle; above it will use the wastegate as well.

Limits and protections operate at every step of the process from driver throttle lookup to wastegate operation, and can limit each of the outputs for each step.

The ECU continuously monitors the engine output by measuring the actual manifold pressure, ignition advance, lambda, cam timing etc and then back calculating the actual torque value using the 'Optimum torque (KFMIOP)' table.  If the actual torque various more than a certain amount from the target torque then the ECU will deem that something is wrong and reduce engine output.  The 'Optimum torque (KFMIOP)' table is indexed by air charge and rpm and the table values are load (torque percentage).  It is the inverse of the KFMIRL table, so if the KFMIRL table lookup produces an air charge of 206% for 80% torque then the KFMIOP table should produce a torque value of 80% for an air charge of 206%.

The ECU also monitors ignition and lambda efficiency as well as wastegate flow.

See Torque parameters for information about tables.