The future of DPF servicing

Change can seem shocking at first, but is it the future?

By Frank Massey | Published:  08 May, 2017

Two months from now will bring my tenure in the motor industry to 49 years. I would like to think I have evolved, kept up with technology, enabling me to provide a professional service, enjoying customer respect and integrity. My focus has been the technical challenges, while my son David manages the commercial responsibilities.

This creates a wide role for me developing our training programme, internal research and development, bringing the focus of this topic to technical and legal compliance.

My chosen subject here is diesel servicing and repairs, specifically particulate filtration and emission control. It is something we have been passionate and vocal over for several years. it gives me no pleasure or satisfaction in seeing our prediction over the demise of diesel vehicles.

Diesel fudge

The future is now clear as to the changes our political lords and masters have in mind. This gives us a short timeline to get our house in order. My intention is to advise, help and warn what will happen if we all continue to fudge diesel particulate repairs as we currently do. Upwards of 90% of independent garages will fall into this category. How do, or should we service and recover diesel particulate filters? The choices are very simple!

1. Replace with a new OE filter

2. Replace with a non-OE filter

3. Clean and service off vehicle in factory controlled conditions

4. Clean and service off the vehicle in house

5. Clean and service on the vehicle

6. Remove the filtration system from the vehicle

Here is the problem; we as professional repairers are legally and financially responsible, and exposed for the advice and decisions we make. This is the case even if the customer agrees and or instructs us on a certain course of action.

Clear legislation is in place for the performance and fitment of diesel emission systems. Vehicle taxation is based on specific emission levels agreed with the manufacturers. I am sure I do not need to mention VW and Audi, but I will bet their corporate accountants have regrets. How long do you think it will be before the government bean counters look at us? Let's not fool ourselves enforcement will take the effect of stringent fines.

Everything

So what are we doing wrong? Pretty much everything. Please remember my words, help, advice and not critique.

We are breaking the law in removing legally compliant systems. MOT examiners will lose their licence by passing unauthorised emission system modification. You will become the first unpaid enforcers.

We are breaking the law further in polluting the water course, by power cleaning, or rinsing out cleaning agents into the drains. Utility companies have powers to set huge fines and often do.

We are also in breach of the clean air act by using some of the available cleaning agents that require the running of the engine whilst emitting all the contaminants back into the environment.

It is quite possible at this point some of you are about to rip out the magazine pages and offer an alternative use for them. Please reconsider, we are slowly killing ourselves.

Let's as an industry get together, think ahead of the curve and get our house and process in order.

Change

I recently visited CERAMEX in Slough, and before a handful out there suspect a paid endorsement here, I even paid my own travel expenses. I have been aware of several companies offering off vehicle cleaning, pressure washing, thermal cleaning in an oven, and ultrasonic treatments. My problem has always been, is the catalytic converter and DPF still fully functional and durable when refitted? How can we protect ourselves from future premature failure due to other indirect causes? Can we provide certification of test results?

Here is my opinion as to how we should address the blocked, cleaning DPF problem. Many of you will not agree, I do not care, this is how it should and eventually will be done. Reflect on the vast changes in the paint refinishing industry before you cry never!

The DPF is initially visually examined bar coded and weighed, attached by means of bespoke plumbing to what is in effect a big dishwasher (sorry Marcus my words) then filled with water. A short pause here, some of you will know water damages and degrades the precious metal wash coat. The purified water has all the damaging trace elements removed and is only used to restrict the clear DPF passages. Pressure waves, are then sent through the core, XPURGE for several minutes. I did question if this was in effect an ultrasonic process? This is not the case. The water does act as a transport mechanism for the waste material, including ash, which is flushed out, into a waste tank. The water is filtered, for reuse and the semi solids captured in large skips for reprocessing. It is pure carbon it would make an ideal fuel source!

The DPF core is then placed in electric air dryers where apart from drying the core, measurements are taken for flow rates and back pressure. Next a two-stage photograph examination is applied to detect face off and ring off cracking to the core. A second weight check is taken to ascertain the mass of soot ash removal. The next service is optional for small vehicle units, the cat and DPF are subject to a sample hot gas bench to establish the reduction of, CO/HC, finally being placed in a particulate bench where filtration is assessed and measured.

Certification

Certification and bespoke transport packaging completes the service. The recovery success is consistently above 90%. The cost is approximately half the cost of a new OE unit. No environmental pollution so your grandchildren will thank you and may avoid the huge increase in paediatric respiratory illnesses.

You will earn profit from a professional repair, enjoy the respect and integrity it brings, however not all customers will agree or want to pay, and that is not our problem.

Further information

Please contact Annette 01772 201 597, enquries@ads-global.co.uk for further information on upcoming training courses and events.

Related Articles

  • Under no pressure 

    Once the news started to spread about my Top Technician win, the phone started to ring with more interesting and challenging jobs, usually ones that have been doing the rounds between other garages without success.
      
     A phone call came from a local parts supplier, a visiting rep was having issues with a DPF. They believed it needed a simple regeneration to get it back on the road and asked if I would be able to do the job. After checking the Blue Print G-Scan, the function for a forced regeneration was available, I believed I would be able to carry it out and booked the job in.

    Basic beginnings
    After traveling from two hours away, the vehicle arrived. The customer was questioned, ‘Why do you require a DPF regen?’ Being a parts rep within the motor trade, her garage visits were frequent; various attempts had been made to resolve the issue. With conflicting advice being given and quotes between £600 - £1200 to fix the vehicle, the customer was obviously confused and unsure about what to do.
        
    The engine management light was on, so the obvious place to start was a scan check for fault codes. The vehicle showed P2002: Particulate Trap Below Threshold.
        
    Viewing the live data for the DPF pressure sensor, key on engine off, displayed a 0kpa pressure reading, a good start for a sensor plausibility check. With the engine running and RPM increased, the sensor reported a suspiciously low-pressure reading, not one I would associate with a saturated DPF. I decided to use the Pico Scope to look at the DPF pressure sensor voltage in real time. After confirming the power and ground circuits to be ok at the three wire pressure sensor, the signal wire was checked. Again key on engine off, 750mv was displayed, a sensor plausibility check and again this was good. Starting the vehicle and increasing the revs revealed exactly the opposite to what I had expected, a negative voltage reading. The voltage should increase as the exhaust pressure increases.

    What’s wrong?
    One area I wanted to check was that the pipes were not connected the wrong way around. I decided to use the Mity Vac to apply pressure to the sensor pipe connected in front of the filter. This showed a positive rise in voltage, further proving good sensor functionality and confirming the pipes to be correctly connected. Connecting the Mity Vac to the pipe after the filter and applying pressure, simulated the negative voltage which was seen when the vehicle RPM was increased, simulating the fault. The sensor pipe in front of the filter must be blocked.
        
    I located the steel pipe that is fitted in the exhaust in front of the filter to reveal soot marks, it had been leaking exhaust gasses. On a closer look it was unscrewed from the exhaust while still located in the hole due to the pipe bracket allowing the slight leak of exhaust gasses. Once the pipe was removed it was clear to see the soot had built up and blocked the small hole in the end of the pipe. I unblocked the pipe, checked to make sure the mounting hole on the exhaust was clear and refitted it.
        
    Using the Pico Scope again on the signal wire, it now showed a positive rise in voltage when the RPM was increased. The live data now showed a small pressure increase, the filter was not blocked. With all fault codes cleared, an extended road test was carried out, the pressure reading stayed low throughout and no fault codes reoccurred confirming the fix, the vehicle did not require DPF regeneration.

    With no parts required to fix the vehicle the repair cost was far lower than the customer expected due to the previous attempts. The vehicle was returned to the customer who was surprised by the
    outcome of the repair and relieved by the associated costs.



    TT Archives:  Top Technician issue nine 2016 | www.toptechnician.co.uk

  • Highs and Lows 

    When faced with diagnosing a fault, in order for us to be able to test the system it is crucial we understand the system’s layout, components and function. We recently faced a fault in a system we had little experience on, so it was an ideal opportunity for a bit of studying.

    Technical information is readily available from many sources, be it manufacturer or generic information, and does not take too long to find. While Google isn’t really a substitute for diagnostics, in situations like this it can be very useful for generic information. The fault on this vehicle turned out to be something so trivial I won’t bore you with it. What I would like to share is the valuable information I picked up along the way.

    Main purpose
    Exhaust gas recirculation (EGR) is nothing new, it’s been used on petrol and diesel engines for many years and while layout and control has varied in design the principle has remained the same. It is important to understand that manufacturers use different methods and configureuration, and for this article I’ve studied several and have tried to demonstrate a generic system.

    The main purpose of EGR is to reduce the level of harmful Nitrogen Oxide (NOx) gases emitted from the vehicle’s exhaust. NOx is present in exhaust emissions due to high combustion temperatures and pressures. Under light load/cruising conditions the EGR system directs a proportion of the exhaust gas back into the engine’s air intake. This reduces the oxygen levels which in turn reduces combustion temperature resulting in a lower NOx emission. When power is required from the engine the EGR system closes to insure a more efficient combustion (see figure 1).

    EGR on/off
    This is the conventional system in its closed (off) position.  During operation exhaust gases are taken from the exhaust manifold (pre-turbo), passed through a cooler (10) up to the EGR Valve (6). The cooler is a heat exchanger that not only uses the engine coolant to cool the gases to increase the mass but utilises the heat to warm up the coolant faster which helps the interior heater warm-up faster. The EGR Valve (6) can be either electrical of vacuum operated. The  powertrain control module (PCM) commands the EGR valve to open by a specified amount dependent on engine conditions (see figure 2).

    Some EGR valves have a position sensor that provides feedback to the PCM to ensure the correct position has been achieved. In a system where the EGR valve is not equipped with a position sensor, the PCM monitors the Mass Airflow signal in order to regulate EGR flow. This is achievable due to the fact that as the EGR valve is commanded open and gases start to flow, the air flowing in to the Mass Airflow Sensor will decrease. The calculation is made using tables of data (mapping) within the PCM’s software. Understanding this is crucial when diagnosing running faults as a fault in the Mass Airflow can easily affect the EGR system and vice versa.

    Understanding and diagnosing airflow and EGR faults I find can be easier if you look at it pressure differential. If air is flowing through a tube with a restriction in it, the air pressure after the restriction will always be lower than the pressure before the restriction. The difference in pressure will vary depending on the mass or pressure of the air and the size of the restriction.

    Air intake/throttle flap
    The air intake/throttle flap (see figure 3) generally defaults to the fully open position while the EGR valve defaults to the closed position. The purpose of the flap is to reduce the pressure on the engine side. As the intake flap starts to restrict the airflow, the pressure decreases to a pressure lower than that of the EGR pressure and the EGR gases start to flow into the engine’s air intake. If the exhaust gas pressure was slightly lower than the air pressure entering the engine then the gases would flow in the wrong direction.
        When in good working order this system serves its purpose. However, due to the fact that there is particulate matter in the exhaust gases, the system and components will slowly become blocked, causing reduced flow and valves starting to jam or not seal correctly. The air intake system often contains oil residue from the engines breathing system and slight oil loss from the turbo itself. When this oil is mixed with the particulates in the EGR gases it makes a very sticky gunk that starts to block the inlet manifold and intake ports.

    When the engine is under load and turbo boost pressure is required, the EGR valve needs to close and seal. If an EGR valve isn’t sealing correctly when closed then boost pressure will be lost into the exhaust system. The lower boost pressure and reduced oxygen level affects the combustion which in turn causes more particulate matter which only adds to the issue. If the EGR valve is stuck wide open then in most cases the engine will barely run.

    High pressure system    
    Euro 6 was introduced in September 2014 which demanded much tighter emissions than previous which required an advance in emission control technology. While the precise control of the fuel side of the engine management system has gained precision with higher fuel pressure and multiple injections within the cycle, the air intake, exhaust and emission control systems have too. Most manufactures use a high and a low pressure EGR system.  Prior to this most EGR systems were relatively simple and fell under the ‘High Pressure EGR’ title (see figure 4 and figure 5).

    The high pressure system is similar in layout to previous systems but serves a slightly different purpose. The system is only used during the warm-up phase of the engine from cold start. There is a pre-turbo passage from the manifold directly to the high pressure EGR valve (6). As the system is only used in the warm-up phase there is no need for a cooler. In this particular system there is a distribution channel that directs the gases equally into each inlet port. The purpose of this system is to raise the intake air temperature in order to improve combustion and reduce the warm-up time for the catalytic convertor/NOx storage catalyst (7) allowing them to function sooner. Once at operating temperature the system is pretty much redundant.

    Low pressure system
    The low pressure system (is active under most engine operating conditions and its purpose replaces that of the older systems- to reduce NOx gases (see figure 6). A proportion of the exhaust gas is collected after the Diesel Particulate Filter (8) and passes through a Wire Mesh Filter (9), through the EGR Cooler (10), up to the Low Pressure EGR Valve (11). The EGR valve then controls the flow through a channel up to the intake side of the turbocharger. The wire mesh filter ensures there is no particulate matter entering the system and also in the event of the particulate filter substrate breaking up, it also protects the rest of the system including the turbocharger, air intake and engine internals from damage. The cooler reduces the gas temperature which in turn increases the mass allowing a higher volume of exhaust gas to be recirculated. Due to the exhaust pressure after the particulate filter being quite low and also the air intake pressure before the turbo charger also being low there is and Exhaust Flap (12) fitted. By closing this slightly the exhaust pressure increases which causes the gases to flow back towards the turbocharger.

    Key benefits
    These systems usually have between three and four  exhaust gas temperature sensors each placed at key points of the exhaust system and two pressure differential sensors. The first is measuring pressure before and after the particulate filter (to calculate soot loading) and second between the DPF outlet and the point after the EGR valve, before the turbo. Coupling these six signals with the Mass Airflow sensor, the positions of both EGR valves and the intake flap, the turbo variable-vane position and the intake pressure (MAP), using the mapping within the PCM’s software means it can also make all calculations necessary. This provides an extremely high intake pressure and exhaust after treatment control.

    The key benefits of this system are that the exhaust gases are free of any particulate matter which keeps the entire system much cleaner and therefore reliable. The gases are also cooler meaning a greater mass can be used in a more effective way. Finally the gases re-enter the system before the turbocharger, allowing for the increase in boost pressures at lower engine load and RPM.

    Does this make diagnosis harder than before? Not if you take the time to study the purpose of each component and how it works. I’ll openly admit it wasn’t that long ago that I would have taken one look at this system and sent it on its way! Nobody likes being beaten by a job but neither should we have to waste too many hours trying to guess what’s wrong with it, worse still start throwing parts at it. It took me half an hour to locate this info, an hour studying it and a further hour planning what tests I was going to conduct and what results I was expecting to see. What was wrong with it in the end? A faulty sensor confirmed with no more than a voltmeter! After replacing the sensor I wanted to confirm the repair and monitor the function of the components using serial data. Something I highly recommend doing is picking five lines of serial data on every car you work on that requires an extended road test and monitoring them to see how they behave and what effect driving style (engine load) has on them. I guarantee after 10 cars you’ll know what to expect and be far more confident in diagnosing related faults. It works for me!

  • Quality street  

    The MOT has gone through change over the past few years. There have been changes in the way the MOT tester and the MOT Centre Manager become eligible to operate a Vehicle Testing Station (VTS) through the qualifications that are available through various national and local training organisations,  through to the MOT tester having to manage their own Annual Training and the Annual Assessment.

    In combination with the revised MOT Inspection Manual (aligning to the European Directive) being implemented during May 2018, some confusion may exist in this ever changing sector.

    The VTS has several people roles that exist, one major role; the Authorised Examiner (AE) or Authorised Examiner Designated Manager (AEDM) being the person having the ultimate responsibility within the business.

    A new VTS and those  changing their approved status will need an AE/AEDM to hold the Level 3 Award in MOT Test Centre Management prior to the VTS becoming approved by DVSA. Most training providers will deliver the MOT Centre Manager qualification. Part of the qualification is that the person understands how to operate a Quality Management System (QMS) for the purposes of the VTS. This has been identified as an area that most people struggle with within the qualification.

    To implement an effective QMS program, the business must initially internally agree the standards that they set. The results are then collected and reported into the QMS. Any problem should have a corrective action. This should be written with an indication the people responsible to carry out the action along with a completion date. If the same problem repeats, then a plan should be developed to improve the situation, and put into action.

    The following highlights a few areas that where the QMS needs to focus.

    Training
    The AE should ensure all staff (employees and contractors) fully understand their responsibilities. This enables them to carry out their job accurately and remain compliant with the necessary requirements.

    The MOT tester should ensure that they meet the requirements of the MOT tester Annual Training and Annual Assessment. This year the annual training includes updating their knowledge of the MOT Inspection Manual which was introduced in May 2018. Most MOT testers will be familiar with the revisions and updates to the MOT Inspection Manual, either through specific training prior to the changes or reviewing the Inspection Manual during its implementation stages.

    The AE should also ensure that the MOT testers that carry out tests at the VTS, are compliant with the requirements. Failure to do so will result in the MOT tester unable to test vehicles. It should be noted that some MOT testers that have not met the requirements have taken many weeks to become reinstated as an MOT tester as a result of non compliance which could reduce business income.

    At present there is no requirement for the MOT Centre Manager to comply with the updating of their MOT knowledge but this could change in the near future.

    Procedures
    The AE should ensure that everyone involved in the MOT testing process within their business has access to key information, especially focusing on MOT test logs and MOT Test Quality Information (TQI).

    TQI can be accessed by both the AE and also the MOT tester, reviewing the MOT test data applicable to their role. The data can indicate both strengths and weaknesses with the MOT testers and the VTS, it is therefore important that this data is regularly reviewed to identify any anomalies within the data and implement an ‘action plan’ to correct any deficiencies, therefore both the MOT tester and the AE have a responsibility in this area.

    MOT TQI was highlighted as a requirement for the MOT tester annual training/annual assessment. It is therefore suggested that the MOT Centre Manager also updates their knowledge on Test Quality Information (TQI) and also MOT test logs.

    The AE should ensure that the relevant people know procedures for the reporting of equipment defects/problems, the equipment maintenance and any equipment calibration requirements within the specified dates as indicated by the MOT Testing Guide. The AE must ensure that any appropriate records (calibration certificates) are kept and the records are held securely.
    The AE should always ensure that the equipment is maintained and calibrated correctly, if a problem is detected (yes things do go wrong) preferable before a breakdown occurs then a clear process should be identified and the rectification of the equipment recorded.

    Assurance
    The MOT tests which are carried out at the VTS must always have the correct result, the security of data, information and passwords are maintained which will lead to the reduction in risk of MOT fraudulent activity. The protection of data used in the MOT process needs to comply with the General Data Protection Regulation (GDPR) which was also introduced in May 2018 replacing the Data Protect Action (DPA) that previously covered the data. The AE has a duty to ensure this has been complied with.
    The process should also include a Quality Control process of the MOT tester to ensure that they produce satisfactory results, and to identify any future weaknesses in their MOT test procedures.

    The MOT Testing Guide (updated earlier this year) indicates that a QC check needs to be performed on an MOT tester every two months. Best practice would indicate that the QC process is completed on each MOT tester more frequently such as every month. The QC check should be recorded and kept in-line with the requirements. The QC report should indicate the strengths and weaknesses of each individual (not just indicating the MOT tester is OK) with an ‘action plan’ (further training etc) on how to reduce the weaknesses. The next month Quality Control report should then indicate how the MOT tester has performed against the ‘action plan’. This could help to reduce the VTS risk score, improving MOT tester performance but also increase business performance.
    Performing and recording quality control checks within an MOT business can be time consuming and often gets forgotten. The person carrying out the MOT QC must be carried out by an approved DVSA MOT tester. The QC can be achieved within the MOT testing team providing more than one MOT tester is engaged (one MOT Tester is nominated as the QC) or alternatively a service that an outside agency could provide. A Vehicle Testing Station with only one MOT tester could have a reciprocal arrangement with a nearby similar business by carrying out the QC check on each other.

    Improvement
    An effective QMS used within the VTS should identify any weaknesses that could put the station at risk. Once a weakness has been identified the business should develop an action plan to improve within the area of weakness. This will typically lead to an improvement.

    All these points will help to achieve a low VTS risk score. The MOT centre manager should read and understand the various documents provided free by the DVSA on how to carry out a VTS risk assessment and to hopefully reduce the VTS risk score.
    The AE can find out more on the qualification by contacting a recognised training provider delivering the MOT Centre Manager Qualification, this will help them better understand the requirements of a Vehicle Testing Station and the various MOT Testing documents and standards associated with MOT testing. Many of these requirements have been revised over the last few years, and it is a requirement for the AE to constantly update their knowledge to remain current. Remember the MOT Testing Guide was revised in early 2018 and many AEs do not have knowledge of the new requirements.

  • 888... Lucky for some 

    With this month’s focus in Aftermarket on cooling, I thought a look at how technology has affected one of the oldest systems of the internal combustion engine. For illustration, I have chosen the Volkswagen Auto Group’s en888 engine, built in Mexico, Hungary and China hence the 888 insignia; It is their lucky number.

    Its one of Audi’s high-performance variants. Its fitted in my Seat Cupra 2ltr, producing 400bhp with stock mechanicals. So, what are the benefits of advanced cooling systems? Heat derived from combustion, transferred by conduction and convection into cooling and the environment is in effect wasted energy. Controlling and where necessary containing it improves efficiency, not forgetting reductions in emission pollution.

    Efforts
    They have made stringent efforts in the mechanical design of the 888 to achieve savings in efficiency. Reducing engine weight, minimising internal friction, increasing power and torque, current with fuel economy initiatives.

    The cylinder block wall is reduced from 3.5mm to 3.00mm. Internal friction is reduced with smaller main bearing journals, revised timing chain design, incorporating a dual pressure lubricating system. The balance shaft has roller bearings, piston cooling jets further improve thermal stability. The jets have PCM mapped control, while extra oil cooling is provided adjacent the filter housing, close to the activation solenoid and twin oil pressure sensors.

    The engine can theoretically reach Lambda 1 from cold within 20-30 seconds.

    Further technical innovations include reduced oil level, reduced tension force in the auxiliary chain mechanism, down shifting achieved with variable valve lift and twin scroll direct mount turbo design.

    Advances
    You will now appreciate that it is no longer possible to separate mechanical design, power delivery, emissions, and all-round efficiency, treating cooling as an afterthought.

    Take the cylinder block design, which possibly has the biggest advances reserved within the cylinder head and coolant control module (water pump). The exhaust manifold is housed completely within the cylinder head casting. This ensures very effective conductance of heat. The emphasis is now on increase, maintain, reduce, thanks to an advanced dual valve PCM controlled coolant control module. The module is mounted at the rear of the engine block, belt-driven with a cooling fan to keep the belt cool.
    By manipulating the two rotary valves, flow and temperature can be effectively controlled within very carefully controlled limits. The rotary valves are manipulated by a PWM 1000hz motor with SENT position feedback (single edge nibble transmission), a method used by the latest air mass meters.

    Heat transfer into and from the turbo is much more efficient due partly to the direct mount and integrated cooling galleries surrounding the exhaust tracts.

    The piston to wall clearance has been increased, with a special coating on the piston thrust side complimenting a direct gudgeon pin to rod contact, the DLC coating removes the need for a bearing bush.

    The cylinder head porting incorporates ignition sequence separation, thus ensuring preceding exhaust pulses do not impede the energy from the current. This in combination with advanced turbine design further improves torque range and downshifting. Cooling control priority is applied to the occupants, then the transmission, further reducing frictional losses.

    Complexity
    Although not directly related to the cooling system, a dual injection system is fitted with its main function being emission reduction. Cold start is provided with three direct injection events, followed by port injection warm up. These systems do not run in tandem. Two thirds of the load range is controlled by port injection, with full load above 4,000 rpm delivered by induction stroke direct fuel delivery.

    From a practical point of view, previous low-tech tasks like replacing coolant components and bleeding now requires electronic support through the serial interface. Using the correct antifreeze is now essential if premature corrosion is to be avoided. As a warning, capillary coolant invasion within wiring looms is well known in some French and GM vehicles, as some of you will be aware.
    It is also worth mentioning that Volkswagen has modified the software controlling cooling in some of their diesel vehicles as part of the emission recall programme.

    Predictably due to their complexity, I can foresee cooling systems being neglected during routine servicing , so expect to see faults as these systems age in the pre-owned market.


  • Well it was like that last year mate! And you passed it then…  

    How many warning lights does it take to create an MOT fail? Put simply, just one - but how many choices do we have?  
        
    Looking through the revised testing manual it’s hard pick out these faults amongst so many changes. Let’s see if we can summarise them for you as a refresher on what fails, some new and some old. Below is a list of
    major failures:

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