11 Points You May Never Know About Truck DPF Filters?

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Categories: Chip Tuning

What is the difference between a 1960’s diesel Bedford truck and 2007 (or later) Common Rail diesel truck?
Well, at the first glance one might be lead to say that the difference is in the highly-tuned precision engineering.  Then we are lead to see the high emission standards these trucks are made to pass.  The term, “Diesel Particulate Filters”  (or DPF) soon pops up.
A diesel particulate filter (DPF) is a part of the exhaust system that spells the difference between diesel trucks manufactured in the nineties and late model diesel trucks. The DPF technology became common from 2007 when many trucks came from the factories equipped with a diesel particulate filter. However, it was not until 2009, when the exhaust emissions standards for new diesel trucks made it mandatory for a DPF to be fitted into the exhaust system of every diesel truck. Such drastic measures were put in place in bid to pass the stricter emission laws.
Taken that the current Euro 5 legislation is set to be replaced by Euro 6 legislation in 2014, the permissible levels of diesel emissions is bound to reduce drastically and as such it is important if not fundamental for every diesel truck owner to get acquainted with a sound knowledge of the DPF and how to deal with it to guarantee a good driving experience while at the same time avoiding getting stuck on the side of the road when the DPF blocks up and the standard regeneration fails to clean the DPF.
Below is a peek as to the 12 things most diesel truck owners will probably never know about the DPF tech installed in the exhaust system of their trucks.

1. Basically, What Is A DPF?

Simple as that may sound, there are some diesel truck owners who don’t know it’s meaning save what the initials stand for. Well, that is understandable taken that one doesn’t have to know every component of a truck’s engine in order to drive it, but as aforementioned with the current campaigns on “How To Go Green”, DPF is a fundamental component of any diesel truck. A DPF is a system installed in the exhaust system of your late model truck and one consisting of two major parts: a filter and a monitoring and a maintenance system.

2. How Does It Work?

The filter in the DPF works by trapping particulate matter (soot) emitted from diesel combustion in the engine while letting other engine gases to flow through. An optimum functioning DPF system traps almost 85% of the soot emitted by the diesel engine of your truck. The trapped soot is burnt off when it reaches a certain threshold.  This constant regeneration (filling, cleaning, filling, cleaning) mode is where the problems start.  More on this later.

3. How To Tell If Your Truck Has A DPF

Euro 4 design diesel trucks will mostly not have a DPF installed as even without it they still meet the requirements in this legislation. However, not many truck owners will be able to comfortably say which legislation their trucks fall under and thus quite a tad tricky to tell whether the truck has a DPF installed or not. Usually DPF engines have different codes to non-DPF engine and these differ from truck models such as Blue, Eco of DPF label on the vehicle model code.  While such codes do tell whether the truck has a DPF, it is wise to consult the owner’s manual or a trusted dealer for clarification. Alternatively, one can look for a large muffler looking part within the exhaust system just after the Cat (if the Cat is not fitted within the DPF itself).  This large muffler type part will have sensors and or pressure pipes running close to the inlet and outlet of the pipe.

4. Active Regeneration To Burn Soot?

Regeneration is the process in which accumulated soot trapped in the DPF is burnt off. While the common belief among many is that for this to occur the truck’s ECU must initiate a raw diesel (or Ad-Blu) fuel injection into the exhaust system to burn the soot, the truth is that some trucks will burn off the soot without having to inject fuel. How is this so? Passive regeneration is where high exhaust temperatures are used to burn the soot independent of fuel injection. In all trucks, the DPS is fitted near the engine (after the turbo) where exhaust temperatures are at their highest to initiate passive regeneration.

5. When To Regenerate?

Regeneration is necessary in order to clean the DPF system, but most truck drivers, though having undergone training on how to handle their diesel engines are at loss when it comes to interpreting dashboard lights indicating the need for regeneration. What happens is that the DPF light is triggered when the filter is 35% – 45% full and loading will continue up to circa 65% at which point the engine management light will illuminate and force the truck to go into limp home mode. At this point, the truck will have to be towed 9or driven in limp mode) to a garage for a forced regeneration or in some worst cases a DPF replacement (which is very costly and is where Chip Tuning can help).

6. High Regeneration Temperatures

Soot burning in either active or passive regeneration will occur at temperatures of 500 -600 Deg Cel and above. Such kind of temperatures cannot be normally achieved at low speeds and thus deterioration of the DPF and limp modes are common.    High temperatures so achieved due to uncontrolled regeneration eventually damage the substrate material of the filters (cordierite, with a melting point of 1200C or silicon carbide with a melting point of 2700C).  Not only that, but the “regeneration” will also decrease fuel economy substantially … often to a point where the vehicle owner wishes he never purchased the truck in the first place!!!  Having the two issues of costly replacement parts, and poor fuel economy is a guarantee of  poor customer satisfaction.  Chip Tuning’s help in removing the DPF (or Ad-Blu) System is a welcome reprieve.

7. False Dashboard Warning Lights

At times, your brand new truck might be getting faulty indicator DPF lamp display without your knowledge. How is this so? The DPF and the accumulated soot impose and additional backpressure on the engine and this pressure so created is detected by pressure sensors located in the exhaust system and information is transmitted to the truck’s ECU, after which the dashboard warning lights may illuminate. A faulty sensor or DPF system (one with cracks or melted internals) might result in inaccurate results that might end up damaging your whole engine with too much exhaust back pressure.

8. Other Load-up Materials in the DPF

The loading state of the DPF is one that continually changes as apart from regular particulate matter (soot and ash) accumulating in the filter. Such ash can consists primarily of incombustible lubricant additives and engine wear and corrosion particles, which are not consumed during the regeneration process. What this means is that despite regular regeneration, your truck’s DPF will ultimately require replacing at one point in time.

9. Non-linear Initial Soot Load-up

Even more confusing is the fact that soot does not load up in a linear manner in the DPF system. Rather, as with most DPF filter materials currently in use, a non-linear initial increase in pressure drop is exhibited. This is because soot first accumulates in the filter pores at the opening near the engine (known as depth filtration) prior to forming a layer on the filter surface (known as cake filtration) resulting into a pressure drop hysteresis that is entirely false as the filter is only quarter or half full thus causing a false regeneration that increases fuel usage and regenerations, and engine back pressure issues even further.

10. Unsuccessful Regenerations

A complete regeneration is achieved by driving at an average speed of 90km/h for around 20 -40 minutes. However, this will not work at times and the extra fuel injected will not burn completely and runs past the piston rings and into the engine’s sump. This causes the oil quality to deteriorate and its level to rise and this makes it really important to check oil levels regularly to make sure that they don’t increase above the maximum level as diesel engines are capable of running on excess engine oil without the owner’s knowledge which ultimately results in engine destruction.  It is surprising to the writer that engine manufacturers are allowing a dilution rate of up to 1:1 (ie 50% engine oil / 50% diesel fuel) until they say its time to to an oil change!  At anything like 10% dilution any automotive engineer will advise to replace the oil.  At 50%, this is incredulous.

11. Faulty DPF Delete Methods

Given the inherent problems that arise as a result of DPFs, most truck owners most often resort to doing away with the whole system in a process called DPF delete. A professionally service conducted either on site at our workshop or remote locations where the factory ECU is sent to Chip Tuning so that we can edit the ECU coding.
This service is called DPF Delete or DPF OFF.  It also involves doing away with the DPF in the exhaust  and installing a DPF Delete pipe in its place (either you or us doing this) then proceeding to remap the ECU to disable DPF loading calculations and regeneration mode as well as to keep the sensors from throwing codes.   Incompetent “tuners” will at times replace the exhaust system only without remapping the ECU which is bound to land you into lots of problems the moment you drive 200kms. Not only that, but also, we edit the ECU is a way that if the Dealer was to plug in their diagnostic tools they will still be able to conduct a manual (or forced) regen so that they do not know any DPF editing has been done on the ECU.   This is our superior remapping solution at work.
Given the fact that modern diesels are highly-tuned pieces of precision engineering, it is wise to consult the services of professional tuners to completely do away with your DPF system and not settle for cheaper local overseas alternatives if they exist.