Group: System Functions (DOC | DPF | SCR)

How do I know whether my DPF is functioning properly or not?

If you see any black smoke or soot residue at the stack or tail pipe outlet, your DPF has failed and is allowing Diesel Particulate Matter (PM) to bypass the DPF and must be replaced. There are several other types of DPF failures that are not as easy to detect because there are no visible signs. Some other common conditions that may indicate that your DPF may not be functioning properly are frequent DPF plugging or your engine may be experiencing shorter intervals between regenerations,

What is diesel particulate matter?

Diesel Particulate Matter (PM) is often referred to as soot. It is the solid component of diesel exhaust that is visible as black smoke. It is comprised of unburned microscopic hydrocarbon particles as well as sulphated ash which is a by-product of engine oil additives that have been burned during the combustion process.

What is a regeneration?

A Regeneration or “Regen” refers to the process where accumulated soot/particulate matter that collects in the DPF is oxidized and burned in the exhaust system leaving residual ash which is a by-product of the combustion of engine oil.

What is passive regeneration?

Passive regeneration refers to the automatic process that takes place in the exhaust system/DPF during normal vehicle operation when exhaust gas temperatures operates between 3500C-5000C (5720 F-9720 F) for sustained periods of time. The temperature at which passive regeneration begins to occur is dependent upon the types and blending percentages of the precious metal coating on the DPF substrate.

What is active regeneration?

Active Regeneration is utilized on vehicles that have a low duty cycle. It refers to the process where exhaust gas temperatures between 3500C-5000C (5720 F-9720 F) cannot be sustained during normal operating conditions. In this instance, an auxiliary ECU controlled system is utilized to increase the exhaust system internal temperatures into the 3500C-5000C (5720 F-9720 F) range to burn off the accumulated soot/particulate matter from the DPF. Active regeneration systems inject diesel fuel into the exhaust stream (post combustion) or into the combustion chamber during the exhaust stroke creating a controlled thermal event that rapidly raises the exhaust temperatures above 3500C-5000C (5720 F-9720 F) to burn off the accumulated soot in the DPF.

What does “duty cycle” refer to?

The Duty Cycle of a diesel engine typically refers to the period of time that an engine operates at a specific engine load factor. In the context of diesel emissions it is often referred to as the period of time that a diesel engine operates within the temperature range allowing Passive Regeneration.

What is a “runaway regeneration”?

An “uncontrolled or runaway regeneration” is a spontaneous uncontrolled thermal event where a high concentration of accumulated soot of a DPF rapidly burns off. It is often caused by high soot load accumulations followed by a period of low power or idle condition. This raises the oxygen content in the flow restricted exhaust. Exhaust gas temperatures can spike to temperatures above 20000 C (36320 F) during an uncontrolled regeneration event causing immediate and irreparable damage to the DPF.

Does a DPF make my engine consume more fuel?

An Active DPF system can increase fuel consumption over older non DPF equipped engines because they use additional fuel to stimulate higher exhaust temperatures post combustion. The fuel penalty with this type of system can be as high as 5% of fuel consumption. As well, as a DPF becomes loaded with soot/PM and ash, exhaust flow is restricted reducing engine power and performance and increasing fuel consumption.

Can I shut off my engine during a regeneration?

Under normal circumstances an engine can be shut off during a regeneration without any harm to the DPF. Once the engine is shut down, the conditions that support regeneration will subside and regeneration will cease. However, caution must be exercised when parking a DPF equipped vehicle to ensure that the exhaust outlet is not exposed to any combustible substances or materials that could be damaged or catch fire by exposure to excessively high temperatures such as shop ceilings, trees and grass etc.

My engine is consuming oil. Can this harm my DPF?

Yes. Consuming engine oil with a DPF equipped engine will poison or cause irreparable damage the catalyst coating on the DPF substrate material. The trace elements that are by-products of excessive amounts of combusted engine oil attach to the catalyst coating creating a “mask” preventing the oxidation process from taking place reducing efficient regeneration regardless of exhaust temperatures. Once a DPF has been poisoned, it must be replaced. A DPF with a high concentration of oil saturated PM is highly susceptible to an Runaway Regeneration.