First post-injection retards combustion inside the cylinder to increase the heat of the exhaust gas. Second post-injection injects fuel late in the power stroke cycle; fuel partly combusts in the cylinder but also sweeps down the exhaust where unburned fuel triggers an exothermal event in the catalyst, raising the filters temperature further.
Active regeneration takes approximately 20 minutes to complete. The first phase is to raise the temperature of the filter to particulate combustion temperature of 500°C+. In the second phase the temperature is raised to 600°C+, the optimum particulate combustion temperature.
This temperature is maintained for 15 to 20 minutes to ensure complete incineration of the particulates captured in the filter. The incinerated particulates produce carbon dioxide and water. Active regeneration is controlled to achieve a target temperature of 600°C+ at the inlet of the particulate filter without exceeding the temperature limits of the turbocharges and close-coupled catalysts.