Diesel Particulate Filter Breakdown and Operational Theory

Diesel Particulate Filter Cutaway

The Diesel Particulate Filter (DPF) is a ceramic filter that has thousands of tiny channels or honeycomb-shaped openings that trap the soot onto the channel walls and prevent the particulate matter (downward to 1 micron) from exiting out the tail pipe. The honeycombed inner structure is covered with a layer of a chemical goad that contains small amounts of precious metals, usually platinum or palladium.

To reduce the particulate matter or soot from the frazzle, you need to raise the combustion chamber temperature high enough to reduce the PM's from forming. NOx is formed when the combustion temperatures exceed three,200°F (1,800°C), and the corporeality of oxide formed depends not only on the temperature, but also the length of time the rut is practical. However, raising the combustion chamber temperature higher inadvertently raises the corporeality of NOx that'southward formed. This is even worse for the environment than the soot.

Diesel cars and trucks manufactured afterward 2009 must have a DPF, and in some cases, a Selective Catalysts Reduction (SCR) organization. These components work together to reduce, and when working properly, remove all of the harmful NOx and soot from the exhaust. Non just does this assistance the surround, it also creates a much cleaner engine. Engine oil doesn't become as dirty as fast every bit it would accept without all of these systems in working order. Less soot mixed with the engine oil means less of that gritty carbon forming in the oil galleys and other moving parts. This increases the life of the engine at the same fourth dimension it cleans the air.

The drawback to all of this is that the DPF needs to exist cleaned regularly. The soot particles attach themselves to the lining of the DPF while the engine is running. At the same time, the filter is slowly clogging with the very particulates that it'southward designed to remove from the exhaust. This process of cleaning the DPF is done through a procedure chosen regeneration. There are several different methods used by various manufacturers to clean the DPF.

Passive Regeneration

Passive cocky-regeneration is completely transparent to the operator and does non touch on the car's functioning or performance. The only indication when a passive regeneration wheel has been activated is either an frazzle temperature warning calorie-free indicating the exhaust temperature is college than normal or a message stating a regeneration cycle is in process, or both.

Active Regeneration

Active self-regeneration occurs when there is not sufficient heat in the exhaust to catechumen the PM being collected in the DPF. The agile regeneration is cocky-activated by the PCM based on various inputs. The PCM sends a command to raise the exhaust temperatures by calculation a pocket-sized amount of injected raw fuel upstream of the DPF. The chemical reaction of the precious metals in the DPF and the raised exhaust gas temperatures oxidizes the PM from the filter.

Stationary (Parked) Regeneration

Stationary, or parked, regeneration is the same as agile regeneration just takes identify while the vehicle is not beingness driven. This is either commuter induced or washed with a scan tool. In that location are times when the driver will need to perform a transmission or "parked" regeneration on the side of the route. This may be because they canceled an earlier regeneration, or an automatic regeneration had started, simply was interrupted. In some cases, the regeneration is "forced" onto the driver for ignoring an before request to perform a parked regeneration by causing the vehicle to go into limp mode. A lot of times, a alarm low-cal or message will tell the driver to pull over and begin a parked regeneration. This usually involves the driver setting the parking brake and engaging a switch to start the process.

Stationary (Parked) Regeneration Precautions

Due to the loftier oestrus created during the regeneration wheel, when performing a parked regeneration or a scan tool-induced regeneration wheel, follow these elementary rules to avoid any outside interference. Stay articulate of combustibles and people.

Filter Failures

Some diesel exhaust filter failures are a result of not allowing the regeneration to have place. This will inadvertently clog the DPF to the bespeak that replacement is the only choice. Although information technology can be cleaned to some degree, a portion of functionality is still lost due to the severity of the restriction. Another problem is when information technology is in regeneration and the excess heat combined with the clog causes the metal casing of the DPF to expand and rupture. Which, of form, means the only solution is to supplant the DPF. The DPF requires professional cleaning every 150,000–250,000 miles or 5000 hours.

Regeneration Monitoring

On some vehicles, the monitoring is done by fashion of a force per unit area sensor that measures the input and output pressures of the DPF. Others utilize mileage or an engine hour counter. On most vehicles, in that location is a way to shut off the regeneration procedure if y'all are in a state of affairs where raising the exhaust arrangement's temperature could crusade a burn down. But, don't leave it off or permanent impairment tin be caused to the DPF.

Regeneration

Regeneration can only happen when the conditions are within the preset specifications for that motor and manufacturer's needs. In full general, virtually regeneration cycles are handled without the driver knowing they are taking place. The regeneration procedure occurs by raising the temperature of the DPF to around 1,100°F (600°C) and enough oxygen is provided direct to the DPF. Some systems will inject actress fuel into the cylinder on the exhaust stroke which effectively sends hot gasses into the oxidation catalyst of the DPF, raising its temperature sufficiently to crusade the carbon to react with the excess oxygen that was also provided. Other systems rely on a heating element just in front of the DPF to raise the temperature.

The regeneration process will continue until the pressure differential across the DPF (input and output) drops to an adequate level. Should the driving circumstances alter, for instance, the automobile comes to a halt and the regeneration is abandoned until the weather in one case over again become suitable. Regeneration can be a noisy thing, equally the engine revs up to iv,000 RPM for four minutes or more than, then goes to 2,000 RPM for an additional 4 minutes or more. When the regeneration has completed, the vehicle will return to its normal idle, and the service light will go back off.

Regeneration Problems

Bug arise when successive regenerations are abandoned, and the soot levels build to a point where the DPF clogs and can't be regenerated on its ain. Brusk trips and end-and-go traffic might non allow the DPF to get up to temperature. When this happens, the driver is notified past a flashing DPF alarm calorie-free. If the alarm light is ignored, and so a second warning appears which tin can cause the vehicle to go into limp fashion. In limp manner, the vehicle will not operate over 5 or 10 mph and will remain that mode until it has been properly serviced using a scanner to perform the regeneration process.

Selective Catalytic Reduction (SCR)

SCR is an culling to the EGR and addresses the same event of reducing the NOx contaminants. This organisation uses a solution of 32.five% urea and 62.five% denatured h2o called Diesel fuel Exhaust Fluid (DEF). This bluish fluid is contained in a divide holding tank that is injected into the frazzle. When the urea mixture meets the hot frazzle gasses, it decomposes to ammonia (NH3) and CO2. The ammonia and so reacts with oxides of nitrogen in a 2d catalytic converter to form a harmless output of nitrogen and water. The advantage is non only a reduction in NOx, but a reduction in the use of the EGR. This means a more efficient combustion, a reduced PM output and improved fuel consumption.