DPF Integrity & Conformity

DPF’s are designed to filter out > 99% of soot particles. Any damaged internal cells allow soot to bypass, rapidly decreasing the efficiency of the unit. Excessive soot loading due to high engine out smoke is the most common cause of DPF failure. When the accumulated soot is combusted the heat generated can cause the cells walls to melt, fracture and become breached. This is commonly known as an “Exothermed” DPF.

Exothermed DPF

A severely exothermed DPF will have melting or cracking of the substrate readily visible, especially on the outlet end. Such DPF’s should be replaced and not refitted onto the vehicle as there will be significant soot bypass.

More moderate DPF failure is not visible simply by looking at the inlet and outlet faces. The Excalibre FSX process checks for failed cells ensuring your DPF is not just clean, but will perform as it should when refitted.

  • Pin test of the outlet cells – predetermined cells are checked using a pin passed down the length of the cells. Any restriction is indicative of exothermed cells and will prevent free passage of the pin.
  • Soot bypass test – the first step in the FSX cleaning machine is to blow air only from the inlet side. If any soot is observed passing through the outlet face then this is confirmation of soot bypass and the number of failed cells is recorded.
  • Permissible levels of failed cells vary from zero for some OE customers up to 5% of all cells for others.
compromised DPF integrity causes excess exhaust smoke

Exothermed or damaged DPF’s can be cleaned but they are generally not suitable for refit to vehicles.





Images 1 & 2 show the inlet and outlet face of a DPF that has been “cleaned” and passed for re-use (not by Excalibre of course). Visually all appears OK. Excalibre were asked to investigate as the vehicle was showing high levels of tailpipe smoke. Our inspection process immediately revealed that there was exotherm damage and soot bypass.

The substrate was then sectioned and the exotherm damage is clearly visible in images 3 & 4.

Don’t rely on a superficial clean and visual inspection – use the Excalibre 7-step process.

Refitting a failed DPF may lead to the following:

  • Soot passing directly out of the tailpipe.
  • Failing of vehicle smoke test.
  • Non-compliance with approval standards.
  • Damage, loss of warranty and premature failure on downstream components.
  • High back pressure causing consequential failures.

Arrange a DPF Clean

Please contact us with your vehicle details to arrange collection of your DPF’s – 01594 887414 or email sales@excalibretech.com
We will then arrange collection by courier. Typical turnaround time is 2 days and shipping is again via courier.

Excalibre specialise in emissions control and commercial vehicle exhausts. We provide a wide range of services and products; including DPF cleaning, remanufactured Euro 6 systems, retrofit SCR systems for Clean Air Zones, and aftermarket sensors & parts.