How Does Diesel Regeneration Work?

The regeneration process burns away any excess soot that has accumulated in the filter, preventing dangerous exhaust emissions and the black smoke that is typically seen when diesel engines accelerate. To meet the EPA’s 2007 pollution limits, engine manufacturers utilize DPFs to trap particulate matter.

How do you trigger a DPF regeneration?

When the DPF warning light lights on the dash WITHOUT the EML / Check engine light, the DPF regeneration / cleaning button should be used. This warning light indicates that the DPF has reached its defined particulate matter limit and requires care, or, to put it another way, it is blocked.

Although the technique for using the button may vary from vehicle to vehicle, the steps outlined below appear to be the standard.

To begin, ensure that you’re in a well-ventilated place, ideally outside. Make sure your car isn’t parked on dry grass or anything else that could catch fire or burn. The filter will become quite hot throughout the DPF renewal operation.

As the procedure begins, the engine revs should grow as the conditions above are met. Depending on how obstructed the filter is, it could take anything from 5 minutes to over an hour. Keep an eye on the engine temperature throughout this period to ensure it does not overheat. The fans should kick in to prevent this, however we recommend that you stay with the car to avoid overheating damage.

When the operation is finished, the DPF warning light on the dashboard will switch off, and the rpm will return to normal idle.

Because this method may vary, we strongly advise that you seek advice on its application from your primary dealer or a specialist. If the EML / Check engine light is illuminated, or the car is in a LIMP or restricted performance mode, your fancy button is unlikely to function.

Should I change the engine oil after the DPF clean?

Following a DPF regeneration, we recommend changing the engine oil, just like a dealer regen. This is because the engine is subjected to extremely high temperatures during the process. We recommend that it be replaced with a high-quality, low-SAPs oil (Sulphated Ash). More information is available on our wildly popular DPF FAQ page.

Why don’t all cars have DPF cleaning buttons?

It is estimated that most vehicles will meet the parameters for automatic DPF regen during mixed driving. Unless the DPF warning light illuminates, most individuals are unaware that the process is in progress. If the light comes on, it usually means the automatic regeneration process has failed and you need to do a DPF regeneration.

Large trucks and 4x4s, for example, spend a significant amount of their lives at far lower speeds than required for autonomous regeneration, necessitating the use of a button.

Please let us know if you have a magical DPF button or if you have any experiences with it in the comments section below.

How often does a diesel do a regen?

Diesel engines emit a lot of soot (particulate matter), which can irritate the lungs and increase the risk of cardiovascular disease.

Since 2009, modern diesel cars have been required to incorporate a Diesel Particulate Filter (DPF) in the exhaust system to prevent soot from entering the atmosphere.

The goal is to reduce particle emissions by 80%, however the technology isn’t without flaws, and our patrols are frequently called to cars with a blocked DPF.

A DPF must be drained on a regular basis to preserve performance.

When the exhaust temperature is high enough, on motorways or fast A-roads, this is normally done passively in a process known as’regeneration.’

  • The ash cannot be removed until the DPF is removed from the vehicle and submitted to a specialist for cleaning, but a well maintained DPF should last far over 100,000 miles.

Active regeneration

Because many automobiles don’t get enough use for passive regeneration to operate, automakers include ‘active’ regeneration, in which the engine control software detects that the filter is becoming clogged and injects additional gasoline into the engine to raise the exhaust temperature and initiate regeneration.

Active regeneration occurs every 300 miles or more, depending on how you drive, and takes 5 to 10 minutes to finish. However, if your journey is too short and the regeneration does not complete, this is a problem.

Don’t ignore a warning light

If a warning light indicates that the filter is blocked, you should be able to complete an active regeneration cycle and clear the warning light by driving at speeds of over 40 mph for 10 minutes or so.

If you ignore a DPF warning light and continue to drive in a sluggish, stop/start pattern, soot will build up in the filter, causing it to go into’restricted performance mode,’ which will protect your car from damage.

  • They may have to replace the filter in extreme circumstances, which can cost up to £1000 plus labor.

In most circumstances, there is only a short period of time between the DPF becoming partially blocked and the requirement for manual regeneration.

The engine management light may illuminate if there’s a problem with the DPF or the differential pressure sensor, which informs your automobile about its health.

What does a diesel do when it regenerates?

The process of regeneration is to burn off (oxidize) the accumulated soot from the filter. This can be accomplished either passively (from the engine’s exhaust heat during normal operation or by adding a catalyst to the filter) or actively (by intentionally putting extremely high heat into the exhaust system). On-board active filter management can take several forms:

  • Engine management uses late fuel injection or injection during the exhaust stroke to raise exhaust temperature.
  • An after-injection catalytic oxidizer to raise the exhaust temperature (HC-Doser)

All on-board active systems consume more fuel, whether to heat the DPF or to provide additional power to the DPF’s electrical system, though the use of a fuel-borne catalyst drastically reduces the amount of energy required. Typically, a computer watches one or more sensors that detect back pressure and/or temperature, and the computer decides when to trigger the regeneration cycle depending on pre-programmed set points. A metering pump can provide the additional gasoline. Running the cycle too frequently while keeping the exhaust system’s back pressure low will result in high fuel usage. The potential of engine damage and/or uncontrolled regeneration (thermal runaway) as well as possible DPF failure increases if the regeneration cycle is not started soon enough.

When temperatures above 600 °C, diesel particulate matter ignites. With the application of a fuel-borne catalyst, this temperature can be decreased to between 350 and 450 °C. The temperature at which soot burns out will vary depending on the chemistry used. The initiation of combustion raises the temperature even more. In the absence of a fuel-borne catalyst, the combustion of particulate matter can generate temperatures above the filter material’s structural integrity threshold, resulting in catastrophic substrate failure. To mitigate this risk, a number of techniques have been devised. Note that, in comparison to a spark-ignited engine, which normally has less than 0.5 percent oxygen in the exhaust gas stream before the emission control device(s), diesel engines have a significantly high oxygen ratio available. While the amount of accessible oxygen allows for quick filter renewal, it also adds to runaway regeneration issues.

Off-board regeneration is used in some applications. Operator interaction is required for off-board regeneration (the machine must be hooked into a wall/floor mounted regeneration station or the filter must be taken from the machine and placed in the regeneration station). Off-board regeneration is not ideal for on-road cars, unless they are parked in a central depot when they are not in use. Industrial and mining applications are the most common uses for off-board regeneration. If non-disposable filters are installed and the regeneration stations are located in an area where non-permissible machinery is allowed, coal mines (with the concomitant explosion risk from coal damp) use off-board regeneration.

Off-board regeneration is used by many forklifts, which is common in mining and other gear that spends its operating life in one area, making a permanent regeneration station practicable. When the filter is physically removed from the machine for regeneration, the ability to inspect the filter core on a regular basis is also advantageous (DPF cores for non-road applications are typically sized to be usable for one shift – so regeneration is a daily occurrence).

How do I know if my DPF is regenerating?

The easiest approach to keep a DPF in good working order is to make sure it can regenerate itself when it’s full of soot (when the warning light appears).

Passive regeneration

Passive regeneration happens when the car is traveling at a high speed on a long highway drive, allowing the exhaust temperature to rise to a greater level, allowing the excess soot in the filter to be burned off cleanly.

To help clear the filter, drivers should give their diesel vehicle a solid 30 to 50 minute run at sustained speed on a highway or A-road on a frequent basis.

However, not all drivers engage in this type of driving on a regular basis, which is why automakers have devised a different method of regeneration.

Active regeneration

When a filter hits a predetermined limit (usually around 45 percent), more fuel is injected automatically as part of the vehicle’s ECU to boost the temperature of the exhaust and burn off the stored soot.

However, if the journey is too short, problems may arise since the regeneration process may not be completed completely.

In this instance, the warning light will remain illuminated, indicating that the filter is still partially clogged.

In that instance, completing a regeneration cycle and clearing the warning signal should be doable by driving for 10 minutes or more at speeds greater than 40mph.

The following signs will indicate whether active regeneration is occurring:

Can I force a DPF regeneration?

  • Check for degradation under heat shielding if the pressure sensor pipes are damaged.
  • The engine oil is the wrong grade for the vehicle; it has to be Low Ash. Check for diesel contamination in the engine oil (could be the result of regeneration)

The correct diagnostic or reset tool must be utilized to perform a forced DPF regeneration. This procedure may take up to 30 minutes. As the exhaust temperatures will be extremely high, make sure the regeneration process is carried out in a safe atmosphere.

Catalytic converters require less maintenance than filters. Engine oil ash accumulates on the filter’s input face, eventually clogging the pores. This raises the pressure drop across the filter, which can cause engine damage if it becomes completely blocked. As a result, filter maintenance is required on a regular basis.

Does DPF regeneration smell?

Many manufacturers have created an active regeneration procedure to tackle the issue that many diesel car owners do not drive in a way that allows passive DPF regeneration. When the DPF filter reaches a specific level of accumulated soot, the ECU sends a fuel injection into the engine to raise the temperature. Your DPF warning light will illuminate if the active regeneration process happens during a short journey and the engine is shut off before it can be finished, indicating that the filter is partially blocked.

Can you regen while driving?

There’s never a good time for downtime, especially when it comes unexpectedly. Forced regens are another issue that many fleet drivers overlook.

Consider yourself fortunate if you haven’t yet encountered this problem. When soot builds up inside the diesel particulate filter (DPF) to the extent where the vehicle is no longer functional, a forced regen occurs. When this happens, the vehicle must pull over and begin a self-cleaning process that can take up to 40 minutes — time that could have been spent driving.

Forced regens, on the other hand, do not have to be the prevalent issue that they are for many fleet drivers. Forced regens can be minimized with one easy adjustment, allowing you to keep your rigs in service longer.

Why regens occur in diesel vehicles

It’s critical to comprehend some mechanics in order to gain the upper hand over forced regens. The type of soot buildup that necessitates a regen happens inside the diesel particulate filter, a specific component of the exhaust system (DPF).

DPFs have become prevalent in diesel-powered vehicles in recent years as a technique of reducing pollutants. Medium- and heavy-duty vehicles are required to fulfill tougher emissions regulations as part of the Clean Air Act, particularly Phase 2 enacted by Congress in 2016. To meet the mandate, the industry began installing DPFs on a larger scale, which trap soot inside a vehicle before it can be released into the air, lowering emissions.

This is accomplished by driving exhaust through a porous ceramic wall, which allows vapor to pass but traps pollutants.

What happens during a regen

DPFs clean themselves periodically to avoid clogging by burning off collected soot. The DPF is striving to “regenerate” itself to its original state, which is why the process is called regeneration.

When everything is working properly, regeneration takes place automatically and unnoticeably while the vehicle is in motion. Soot is burned off the DPF as rapidly as it collects, thanks to the heat of the exhaust. Passive regeneration is the term for this.

When the exhaust isn’t hot enough to burn off soot on its own, the vehicle can pump fuel into the DPF, raising the temperature and allowing the soot to be burned away. Active regeneration, as opposed to passive regeneration, is usually unnoticeable by the driver.

When normal regeneration is insufficient to burn away soot, danger ensues. A forced regen is required in these circumstances, and the motorist must pull over and wait while the DPF completes a more thorough self-cleaning operation. Failure to undertake a forced regen when your vehicle’s indicator system alerts you to do so can result in serious engine damage.

How to reduce forced regens

The good news is that forced regens don’t have to be a constant annoyance if drivers restrict the amount of pollutants entering the DPF from the start.

DPF regeneration can be reduced by using a premium diesel fuel like Cenex Roadmaster XL. Roadmaster XL provides a cleaner, more complete burn thanks to an additive mix designed to match the demands of today’s high-performance diesel engines. Roadmaster XL can assist prevent soot-related difficulties like forced DPF regens by minimizing soot during combustion.

DPFs will likely continue to play a role in the industry for the foreseeable future, with Phase 2 emissions restrictions affecting rigs through model year 2027. Learn how Roadmaster XL helps keep your DPF clean and your operation running smoothly.

How long does it take to do a parked regeneration on a diesel?

When soot builds up inside the diesel particulate filter (DPF) to the extent where the vehicle is no longer functional, a forced regen occurs. When this happens, the vehicle must pull over and begin a self-cleaning process that can take up to 40 minutes — time that could have been spent driving.

Does a regen stop on its own?

A parked regen is managed by the computer system in your truck and simply requires that certain circumstances be met. The procedure should take no more than 45 minutes to an hour. Something is wrong if your parked regen takes longer than this or doesn’t finish. Take your truck to a mechanic as soon as possible to get it looked at.

The idle returning to normal speed, a clear smell of burnt soot coming from the tailpipe, and an increase in temperature on the exhaust components throughout are all evidence that your parked regen has completed successfully.