ICE-23 — The Diesel Particulate Filter (DPF)

ASSUMPTION — Regeneration thresholds and fill levels vary by system; a qualitative framework is given.

In this lesson you will learn:

• How the DPF traps particulates
• The regeneration process
• The back-pressure trade-off

1. Why Is It Needed?

Diesel combustion produces particulates (soot), especially at high load. The DPF physically traps them.

FACT — The DPF is a porous wall-flow filter; exhaust passes through the walls while particulates are trapped. As it fills, regeneration cleans it.

2. Regeneration

Regeneration burns (oxidizes) the accumulated soot.

• Passive — soot burns spontaneously when exhaust temperature is high enough.
• Active — the ECU raises exhaust temperature via post injection when it is not high enough.

FACT — Active regeneration consumes extra fuel (to raise exhaust temperature) — a temporary efficiency cost. Incomplete regeneration can clog the filter.

3. Back Pressure

FACT — The DPF adds flow resistance (back pressure) that grows as it fills, reducing efficiency. Fill level is monitored (differential pressure sensor) and regeneration is scheduled.

4. Trade-offs

INTERPRETATION — The DPF greatly reduces particulate emissions but adds cost, weight, back pressure and regeneration fuel. Calibration manages the emissions target vs efficiency/smoke balance.

5. Summary

• DPF traps diesel soot.
• Regeneration is passive or active (post injection).
• Back pressure reduces efficiency; fill is monitored.

6. Sources

• Bosch, Emissions Control Technology
• Bosch, Diesel-Engine Management

Next Lesson

• ICE-24 — SCR: selective catalytic reduction for NOx.