MDZW 1.120 (Calculating Torque at the Desired Ignition Angle)

MDZW 1.120 Function Description

When calculating the desired ignition angle there are three different cases:

1. Torque influence on the ignition angle active (B_zwvs = 1)

2. Switching off torque influence on the ignition angle (B_zwvs = 0, dmaufr_w> 0)

3. Torque influences inactive (B_nozwe = 1)

1. Active Torque Intervention

The enable condition (B_zwvs) condition is set and the switch-off condition for the ignition angle intervention (B_nozwe) is false. The desired ignition angle is calculated from the torque requirement for the ignition path mizsol_w. The perturbation ramp (dmaufr_w) is zero. The requested torque mizsol_w is converted into the desired efficiency etazws. This is done by dividing by the optimum torque, which is calculated by multiplying miopt_w with the efficiency etazaist. The desired efficiency (etazws) is converted via the inverse ignition angle efficiency characteristic DZWETA into a delta-ignition angle (dzws). The difference between the optimum ignition angle zwopt and dzws gives the desired ignition angle zwsol.

2. Switching off the Torque Influence

When switching off the torque intervention (B_zwvz = 1®0, see %MDKOG), the desired torque mizsol_w can jump to a higher value. This positive torque perturbation must be prevented for driveability reasons. This is done by eliminating the requirement B_zwvz. A perturbation ramp dmaufr_w is reset, which initialises the amplitude of the jump and runs down to zero with a speed-dependent rate. This ramp is subtracted from the input mizsol_w and ensures a smooth transition into a state without any intervention within the timeframe. In this state B_zwvs = false, the switch-off condition for the ignition angle intervention B_nozwe is set but only after the ramp.

A special case is the anti-judder feature intervention, in which B_zwvs, but not B_zwvz is set. When the anti-judder torque requirement is eliminated from input mizsol_w, there is no jump, so that the switch-off ramp in this case is not necessary.

3. Torque Influences Inactive

In this state, no requirement is active (B_zwvs = 0) and the ramp dmaufr_w is screened. The switch-off condition for the ignition angle intervention B_nozwe is set. In this case, the desired ignition angle zwsol for the ignition is not taken into account (c.f. %ZUE) so the calculation can be omitted.

MDZW 1.120 Application Notes

The values ​​are in DMAUFN are preset to give a slope of approximately 5%/sec for all engine speeds.