Cold Start Emission Reduction Strategy Monitoring

All parameters that are relevant during the catalyst heating phase are monitored by standard monitoring functions:

e.g. MSD80-N54

During catalyst heating, it is essential to ensure that enough thermal energy is applied to the catalyst in order to heat it up as quickly as possible.

Therefore, the ignition timing should be limited to the earliest possible value during the catalyst heating phase.

When there is a demand for more torque and, therefore, for advanced ignition timing beyond the limits, the engine is allowed to stall instead of fulfilling the demand.

The torque limits are calibrated in this way so that the emissions remain below the threshold value of 1.5 times the limits.

Known System: 

During normal driving, the ignition timing desired torque corresponds to the air mass desired torque, which determines the ignition timing. During the catalyst heating phase, the catalyst heating torque is added to the air mass desired torque, resulting in a higher reference air mass torque.

Ignition timing is determined by the efficiency, i.e. desired torque divided by the reference torque.

New System (BMW-development): 

The earliest possible ignition timing is determined by limiting the torque reserve to a minimum value during the catalyst heating phase. In order to achieve this, the required minimum catalyst heating torque is subtracted from the reference air mass torque. The reduced efficiency then results in a safe ignition retard and limits the ignition timing during the catalyst heating measures.

The ignition timing is limited to the earliest possible ignition time during the catalyst heating phase by limiting the torque reserve to the minimum required torque reserve:

Maximum Ignition Timing after Cold Start with New BMW Method: