A DPF enables diesel vehicles to minimise their harmful exhaust emissions.
A Diesel Particulate Filter (DPF) is an after-treatment device attached to the exhaust system of diesel engines that reduces harmful exhaust emissions, primarily NOx, particulate matter (PM), and unburned hydrocarbons (HC). It works by removing tiny particles from the engine's exhaust gases. This mitigates the negative impact of diesel cars on the environment.
The main component of a DPF is a sintered metal substrate containing high levels of vanadium and iron alloys. As soot passes through this substrate, molecular compounds are deposited at high temperatures in order to reduce soot volume and weight without being consumed by the process. As soot builds up on the filter material, it begins to restrict flow. The build-up of the soot leads to combustion inefficiency. For the DPF system to regain efficiency, it has to pass a regeneration process. There are three regeneration process options; active regeneration, passive regeneration, or forced regeneration. Active regeneration and passive regeneration occur during normal engine operation.
During passive regeneration, high exhaust temperature is required to combust the excess soot deposited in the DPF filter into carbon dioxide. Extra fuel is injected into the exhaust stream upstream of the filter to vaporize and clean the particulate from the substrate. This will smoothen the flow enabling the DPF to continue to function. Alternatively, when a diesel vehicle runs at a high sustained speed and load, the temperature of the exhaust gas stream rises. The increased exhaust temperature incinerates the excess soot which exits the car's DPF as carbon dioxide. This process is referred to as passive regeneration or "self-cleaning."
Blocked diesel particulate filters can also be cleaned using the active regeneration process. In this process, sensors in the car's powertrain control module track the exhaust temperature and pressure differences at both ends of the DPF unit. Suppose the pressure limits are below the threshold. In that case, the system increases fuel injection before it enters the diesel oxidation catalyst (partial filters) and the DPF and uses a heater to raise the temperature to burn the harmful soot before it exits the exhaust. The active regeneration process produces ash as a by product. In addition to the engine oil and extra fuel, filters require a third fluid known as a dosing fluid. The function of a dosing fluid is two-fold: 1) it carries heat away from the substrate during regeneration 2) it transports ash materials away from downstream components for disposal after regeneration has been completed. The type of dosing fluid used will vary by application, but the most common examples would be solvents, water-glycol, cooling fluid, or oil.
If both active and passive regeneration fails to unclog the DPF, the check engine and DPF warning light will come on. If the DPF warning light pops out, the vehicle should be driven slowly or not be operated at all until a DPF replacement is completed. Ignoring the DPF light risks damaging the DPF completely. After the warning lights pop out in some diesel fuel cars, the car shifts to a limp mode, cutting power to prevent further engine damage. Forced regeneration is carried out at specialized service centres by qualified mechanics. Specialized tools are used to force the diesel particulate filters to regenerate. The process can succeed or fail. If the regeneration cycle is not successful, your only option is buying a replacement DPF.
The temperature inside the DPF is increased by running the engine under no load (i.e., not towing or hauling) at high idle until the regeneration event has been completed, typically after between 3 and 15 minutes of operation. Once complete, normal engine operations can resume.
A DPF can potentially be overwhelmed by excessive fuel usage during regeneration. This problem, known as "fuel pre-mature shutdown," occurs when excess fuel enters the exhaust stream before it has burned completely in the combustion chamber and becomes trapped inside the filter. When this occurs, the filter temperature is raised to such a high level that the substrate begins to degrade and eventually fails, resulting in an emergency regeneration event. In addition to fuel-based problems, oil can also be drawn into the combustion chamber after being ingested by the engine's oil pump. When this occurs, the regenerative process will not complete due in part to incomplete combustion occurring in the engine cylinders and also in part because of reduced heat transfer rates and increased temperatures inside the DPF when compared with normal operating conditions. This type of problem is referred to as "oil pre-mature shutdown." It typically results from higher than expected pressures within either or both of the lubricating oil systems (the crankcase or common rail).
Each engine manufacturer has an established mileage limit at which a regeneration event must occur for the proper operation of its particulate filter. This value is typically between 5,000 km and 30,000 km for heavy-duty engines but could be as low as 1,500 or as high as 120,000 for light-duty applications. Exceeding this interval without initiating a regeneration event may lead to degraded performance. In extreme cases where total soot volume exceeds the design capacity of the filter substrate, clogging of the substrate may occur, leading to a complete loss of engine power and/or reduced fuel efficiency.
A completely clogged or "full-off" DPF will require replacement in order to restore proper engine operation. In some cases where the only partial blockage is present, an emergency regeneration event can be initiated by forcing additional fuel into the exhaust stream, which causes the filter temperature to rise above allowable limits allowing the release of accumulated soot from the filter substrate. This type of problem can often be more damaging to the vehicle's emissions system than a complete failure as all types of vehicle emissions components are exposed to higher concentrations of harmful pollutants under these conditions. While it is possible that a complete failure of a DPF does not result in the release of these harmful pollutants into the atmosphere, most automotive manufacturers do not recommend driving vehicles with a failed DPF as there is no guarantee that engine performance will be sufficient to prevent damage from excessive soot loading.
A diesel particulate filter is mounted to the engine's exhaust system. It is typically located between the turbocharger and the engine's catalytic converter. The location of this filter has an impact on its performance as it must remain submerged in the hot gases coming out of the engine. If for whatever reason, these gases are unable to make their way through the DPF (often due to blockage), they will instead be forced back into the combustion chamber, where they can interfere with normal combustion processes. This problem is known as "backfire."
A brand new DPF typically costs between $1,000 and $3,000 plus installation labour costs depending on the make and model of the engine. In some cases, it may be possible to repair a clogged DPF by removing the compromised substrate and installing a replacement cartridge. This approach can reduce labour costs but will not restore performance or prevent another regeneration event from occurring again in the near future.
A diesel particulate filter cleaning service is an option that allows you to clean out your own vehicle's DPF prior to replacing it with a new one which can potentially save hundreds or even thousands of dollars in unexpected replacement costs. In most cases, this service will be offered at local automotive aftermarket parts retailers for between $200 and $400, depending on the make and model of the vehicle.
Typically, these types of services are performed by removing the clogged substrate from the filter cartridge assembly without damaging it so that it can be re-installed into the engine later. This process typically involves using compressed air to force cleaning solution through the filter media while simultaneously vacuuming out any loosened soot from the filter housing. The filter is then re-assembled and reinstalled into the vehicle, where it is left to run for an extended period of time in order to allow any cleaning residue to be burned off.
Many car drivers who experience DPF problems typically notice that their vehicle will begin emitting black smoke out of its exhaust pipe. This occurs as a result of unburned fuel accumulating within the engine's cylinders which causes them to misfire, leading to incomplete combustion processes resulting in elevated quantities of unburnt hydrocarbons making their way through the engine's catalytic converter, where they are eventually released into the environment as harmful pollutants.
Desist from driving the car frequently on low fuel. Maintain the fuel tank filled up at least to quarter tank. The vehicle systems may attempt to bypass the DPF to save fuel when the fuel tank is low on gas. Please do not ignore the orange light when it shows up on your dashboard. Avoid performance modifications known to damage or strain diesel vehicles. In some cases, removing the DPF for performance enhancement may invalidate your car insurance policy. Finally, refer to your car manufacturer owner manual on best DPF maintenance practices.
For those drivers who often use their vehicles under severe driving conditions such as high-speed highway driving for long periods of time, there are also aftermarket additives designed especially for diesel applications which can reduce harmful deposits from adhering to internal components throughout the combustion cycle.
Typically, DPF sensors are sturdy devices that can be fitted into almost any diesel engine to monitor the buildup of harmful pollutants within a vehicle's exhaust system. In most cases, these components will be fitted with a small metal oxide semiconductor field-effect transistor (MOSFET) chip specifically designed for detecting various chemical changes causing a change in its electrical properties.
These chips contain very thin layers of conductive material separated by non-conducting oxides, which allows them to both produce and sense an electrical potential when exposed to certain substances such as oxygen, carbon monoxide, or sulphur compounds, among others. For more information about vehicle emissions, take a look at the Australian Government's Green Vehicle Guide.While diesel particulate filters are designed to reduce emissions produced by modern diesel engines, their ability to function properly can be severely impeded if they become clogged with soot particles over time. In order to keep your vehicle running properly, it is important to have this type of component regularly cleaned at local auto parts retailers or dealerships. This will typically involve using pressurised air to force cleaning solution through the filter media while simultaneously vacuuming out any loosened soot from the filter housing. The filter is then re-assembled and reinstalled into the vehicle, where it is left to run for an extended period of time in order to allow any cleaning residue to be burned off.
Diesel engines emit significantly more pollutants into our environment than their gasoline-powered equivalents, which is why many governments impose strict regulations on vehicles equipped with these types of powertrains. Equipping modern-day diesel-powered vehicles with DPF systems makes it possible to reduce harmful exhaust soot emissions by up to 90% without compromising engine performance. This makes them an attractive proposition for drivers who do not wish to compromise on either affordability or fuel efficiency.