Deciphering DPFs

Deciphering Dirty DPFs

With autumnal temperatures plummeting and MOT demand rising, garages should expect an increase in reported DPF problems, leading Rob Marshall to research how the current situation impacts technicians, striving to execute high-quality solutions

Autumn may bring seasons of mists and mellow fruitfulness (according to our more knowledgeable editor, the line is from the pen of John Keats, not a 1990s Mr Kipling Cakes advert as I thought), but it also heralds the start of peak diesel particulate lter (DPF) season. With the hullabaloo surrounding DPFs, one would be led to believe that they have been tted deliberately to rob motorists of cash and technicians of their sanity. However, the truth is that DPF problems tend to be caused by something else. Therefore, dealing with a blocked DPF alone is only the rst step of a multi-faceted repair process. DPF Doctor Network training, for instance, uses the analogy of an over owing bathtub – you will be mopping the oor forever, if you do not turn o the running taps. The same situation applies to cleaning the DPF continually – you must address the underlying issue.

As our previous article on additives details, DPF soot blockages can be caused by contamination elsewhere in the engine and fuel injection system. Yet, it can also be caused by mechanical faults, such as compression leaking past fuel injector seals. These facts are relatively easy to relate to a customer. The delicate matter of trying to explain that their driving may be to blame may risk a smack-in-the-mouth and should be explained tactfully to avoid o ence.

DPFs can block with soot and historical residues, such as those caused by infrequent oil changes, or a low SAPS lubricant not being used. Poor quality additives can also cause great harm.

OFF-CAR DPF CLEANING

Several companies o er mail-order DPF cleaning services, the main disadvantage for garages, of course, is taking the DPF o , which is not easy on some vehicles, and storing the vehicle until the cleaned part is delivered. Thankfully, quality specialists o er a fast turnaround. Since launching the operation towards the end of 2020, Carwood reports that it has witnessed a marked growth in demand for its o -car cleaning services. While some of this has been down to DPF issues resulting from some car owners trying to reduce maintenance costs, by extending service intervals, it is encouraging that some drivers understand that a free- owing, clean DPF enhances engine performance and emissions, yet cuts fuel costs.

Carwood reports that its bio-enzyme cleaning agent cleans throughout the lter structure and eradicates any residual matter, including all PM10 particles, cerium and oil deposits to restore the DPF to 98% of the OEM’s original capacity. The main advantage is that, while on-car cleaning methods remove lighter ash layers, they cannot touch the stubborn, thicker crusts of ash, which is more problematic. The company reveals that, while surface ash reductions may provide an initial improvement in DPF performance, remaining deposits will harden on the DPF cell walls, eventually. Carwood concludes that its o -car cleaning solution cuts through even the hardest to remove ash, which is not possible by other methods.

Many technicians are aware that short journeys and low speeds do not permit the exhaust system to heat su ciently to burn o DPF soot accumulations. Again, helping the customer to understand this, as well as researching and selling suitable additives as preventative measures, will prove bene cial for all parties. Yet, poor driving techniques can also hinder the active regeneration cleaning process. Erratic throttle pedal control, especially when allied to sudden bouts of acceleration that is followed by sharp braking, can also discourage regeneration from completing successfully. It may be worth joining the owner for a test drive, while looking for these undesirable driving traits, and (possibly) hunting for the most diplomatic way of explaining that the DPF might bene t from smoother driving techniques...

The preventative procedure

To maintain your high-quality reputation, your goal should be preventing problems from happening. Keeping in touch with regular customers is essential, especially if a scheduled service is due before the winter. The DPF Doctor network advises garages, which look after particulate lter-equipped vehicles, use a professional oil ush additive, prior to adding a fuel system cleaner, such as JLM’s Diesel Emissions Reduction Treatment, or GDI Injector Cleaner for petrol engines thus equipped. Should you suspect that a regular diesel-driving customer is going to conduct regular short runs at low speeds, it is worth emphasising the value of undertaking a 40 minuteslong journey at least once per week, so the car can complete an active regeneration cycle to keep its DPF clean. While a customer might complain about the resultant fuel costs, it is worth explaining that the repair invoice associated with an overloaded DPF will result in even higher expenditure. With household budgets forecast to be stretched considerably over the winter, highlight that ignoring DPF-related lamps is a false economy but state that you are on-hand to o er advice and support, should one illuminate.

Do not forget the role contamination plays with premature DPF lling. Decent quality engine and fuel system additives will help.

The quality connection

Clearly, garages cannot deliver high-quality solutions with neither decent training, nor trustworthy uids. Take the fuelborne 'Eolys' additive systems that DPF-equipped Peugeot and Citroëns employed initially over 20 years ago as examples. This is the same technology that has spread to other brands, Mazda and Volvo included. Despite extra complications of additional additive tanks/pouches, plus pumps and ECUs, they work surprisingly well. Yet, a quality additive is key to making the soot deposits vapourise at lower temperatures. This Eolys uid survives the combustion process and encapsulates the soot particles with a coating that burns at a lower temperature than the soot. Once it combusts, it creates su ciently high temperatures to vapourise the soot. However, since this

DPFs blockages tend to be caused by external factors. Damaged intercoolers, or boost hoses, are common issues that lead to rapid DPF soot lling.

TOP 5 DPF CUSTOMER QUESTIONS

The DPF Doctor, Darren Darling, emphasises the importance of being a detective. Obviously, you do not wish any customer to feel put on the spot but you need to extract truthful answers. Therefore, before the customer has left the premises, you should ascertain:

1. What is the car's service history? Not only look at whether, or not, it has been performed regularly but also if it is up to date.

2. What is the customer’s driving style and under which conditions is the car used primarily? For instance, it is mainly urban stop-start conditions, short shopping trips, long motorway runs, or a wide variety?

3. Has any other garage or mechanic tried to resolve the current issue already and, in particular, were fault codes cleared?

4. Is the car tanked with branded fuels, from supermarkets, or a mix of the two sources? The answer gives an indication of possible engine condition, including injectors, turbochargers and the EGR circuit.

5. Has the customer, or a previous mechanic, used any in-tank additives to try to resolve the issue? This is essential, because overuse of DPF regeneration additives, particularly those with budget formulas that utilise iron-based catalysts, can cause DPF overheating to such an extent that the core can melt.

Self-dosing fuel-borne additive systems can only work with a quality additive. Recent research from CDTi highlights that low-quality additives are entering the independent garage trade. Pictured here is an early version of the Peugeot/Citroën Eolys additive system, showing post injections that are used to facilitate active regenerations.

additive needs replenishing at set intervals, aftermarket businesses have provided cost-e ective alternatives to main dealer uids.

One of the best-known of these is PatFluid, formulated and sold by CDTi of Gatwick, West Sussex. While the company views competition as welcome and healthy, it has discovered relatively inexpensive Eolys-replacement fuel-borne additives being o ered to the aftermarket that are making DPF blockages and damage more likely. This is because uid formulations require a particular quantity of catalysts to work properly. CDTi has laboratory proof that some of these tempting products contain between 50 and 95% less of these active ingredients, compared to both PatFluid and OEM o erings. The company reports that, while it also evaluates competitor products, these more recent entrants are very di erent and CDTi reasons that it is both right and fair to inform the aftermarket about them, especially as they are being o ered by some motor factors and part distributors. AT understands that CDTi is conducting further research in this area and we look forward to bringing you its future ndings, when they become available.

DPF NEWS

Love them, or loathe them, Diesel Particulate Filters are here to stay. The current MOT requirements involve physical checks to ensure that they are present, unmodi ed, or defective. Yet, in February this year, a Private Members' Bill was presented to the House of Commons by Barry Sheerman, MP for Hudders eld that questioned the e ectiveness of the visual checks at MOT time. Arguing that the current system is out-of-date and captures only 1% of faulty lters, Mr Sheerman called for the DVSA to adopt mandatory exhaust emissions testing for ultra ne particulate matter. Naturally, this will involve testing stations with an extra burden to procure the equipment. It was revealed that, in the Netherlands, 10 workshop devices were set to be approved by this summer to perform this operation. The bill was read for the second time in May 2022. For more information about its progress, check out https:// bills.parliament.uk/bills/3113.