[AlanHo]

A neighbour who is a car technician attended a training seminar on diesel maintenance.

He was provided with the following information on Diesel Particulate filters. It was explained that each manufacturer uses their own proprietary methods for DPF control – but this is the general procedure used by most.


Diesel Particulate Filter

Diesel emissions are 90% lower than they were in the 1980s; however exhaust regulations based on statistical studies dealing with the health impact of exhaust emissions continue to demand even lower gaseous and particulate diesel emissions. Particulate emissions are responsible for the characteristic black exhaust fumes emitted from the diesel engine. They are a complex mixture of solid and liquid components with the majority of particulates being carbon microspheres on which hydrocarbons from the engines fuel and lubricant condense. In order to comply with the strict European Stage V emission standards, all european diesel vehicles must now be fitted with an exhaust emission control system to reduce particulates to a specified standard.

The primary component of the system is the diesel particulate filter (DPF), which has been proven to be effective in reducing particulate emissions to negligible levels. The main ability of the particulate filter is its capacity for regeneration; that is burning the particulates trapped in the filter at calculated intervals in such a way that the process is unnoticed by the driver of the vehicle.

Operation of the Diesel Particulate Filter

To enable the exhaust emission control system to store and when conditions determine, burn the particulates, the diesel particulate filter uses filter technology based on a filter with a catalytic coating. Made of silicon carbide the filter is packaged into a steel container installed in the exhaust system of the vehicle. The filter has good thermal shock resistance and thermal conductivity properties, plus a closely controlled porosity. The filter is tailored to the engines requirements to maintain the most favourable exhaust backpressure.
The porous substrate in the filter's interior consists of thousands of small parallel channels running in the exhausts longitudinal direction, adjacent channels in the filter are alternately plugged at each end. This arrangement forces the exhaust gases to flow through the porous walls, which acts as the filter's medium. Particulates that are too big to pass through the porous walls are left behind and stored in the channels. To prevent the particulates creating an obstruction to the exhaust gas flow, the filter system provides a regeneration mechanism, which involves raising the temperature of the filter to such an extent that the particulates are incinerated and as a result removed from the filter.

The most important parameters influencing filter regeneration are the temperature of the exhaust gases and filter. With this in mind the composition of the filter also includes a wash coating to the surface of the filter comprising platinum and other active components; materials used in the manufacture of oxidation catalytic converters. At certain exhaust gas and filter temperatures the catalytic coating promotes combustion and therefore burning of the particulates, while also oxidizing carbon monoxide and hydrocarbon emissions.
Exhaust gas and filter temperatures are controlled by the ECU. The DPF module monitors the load status of the particulate filter based on driving style, distance driven, and signals from the differential pressure sensor. When the particulate loading in the filter reaches a threshold, the filter is actively regenerated by adjusting, in accordance with requirements of the various engine-control functions; such as: fuel injection, intake-air throttle, glow-plug activation, exhaust-gas recirculation, and boost-pressure control.

This control function is made possible by the flexibility of the common-rail fuel injection engine in providing the precise control of: fuel-flow, fuel pressure, and injection timing, all of which are essential requirements for an efficient regeneration process. After-market re-mapping of the ECU or the fitting of plug-in tuning boxes may interfere with this fine balance and lead to premature DPF failure.

Two processes are used to regenerate the particulate filter, 'passive regeneration' and 'active regeneration' both of which are discussed below:

Passive Regeneration

Passive regeneration involves the slow environment-protecting conversion of the particulates deposited in the filter into carbon dioxide. This regeneration process comes into effect when the filters temperature reaches 250*C and occurs continuously when the vehicle is being driven at higher engine loads and speeds. No special engine management intervention is initiated during passive regeneration, allowing the engine to operate as normal.
Only a portion of the particulates are converted to carbon dioxide during passive regeneration and due to chemical reaction this process is only effective within the temperature range of 250*C to 500*C. Above this temperature range the
conversion efficiency of the particulates into carbon dioxide subsides as the temperature of the filter increases.

Active regeneration

Active regeneration commences when the particulate loading in the filter reaches a threshold as monitored and determined by the DPF module. This calculation is based on driving style, distance driven and exhaust backpressure signals supplied by the differential pressure sensor. Active regeneration generally occurs approximately every 400 kilometers (250 miles) although this will depend on how the vehicle is driven.

For example, if the vehicle has operated for a length of time at low-loads for instance in urban traffic, active regeneration will be initiated more often. This is due to a more rapid build up of particulates in the filter than if the vehicle has been driven periodically at greater speeds, where passive regeneration would have occurred. A mileage trigger incorporated within the DPF module is used as a backup for initiating active regeneration. If after a threshold distance has been driven and regeneration has not been activated by backpressure signals; regeneration will then be requested on the basis of distance driven.
Active regeneration of the particulate filter is started by raising the temperature in the particulate filter up to the combustion temperature of the particulates. A principal method of increasing the exhaust gas temperature is by introducing post-injection of the fuel, that is after the pilot and main fuel injections have taken place. This is achieved
by the DPF module processing signals from the temperature sensor to determine the temperature of the particulate filter and depending on the filters temperature, the DPF module commands either one or two post-injections:
First post-injection retards combustion inside the cylinder to increase the heat of the exhaust gas.
Second post-injection injects fuel late in the power stroke cycle; fuel partly combusts in the cylinder but also sweeps down the exhaust where unburned fuel triggers an exothermal event in the catalyst, raising the filters temperature further.

Active regeneration takes approximately 20 minutes to complete. The first phase is to raise the temperature of the filter to particulate combustion temperature of 500*C.
In the second phase the temperature is raised to 600*C, the optimum particulate combustion temperature. This temperature is maintained for 15 to 20 minutes to ensure complete incineration of the particulates captured in the filter. The incinerated particulates produce carbon dioxide and water.

Active regeneration is controlled to achieve a target temperature of 600*C at the inlet of the particulate filter without exceeding the temperature limits of the turbochargers and close-coupled catalysts; refer to 'Active Regeneration Protection Limits' below.

During the active regeneration period: The turbocharger is maintained in the fully open position to minimize heat transmission from the exhaust gas to the turbocharger and to reduce the rate of gas flow through the particulate filter. This enables optimum heating of the particulate filter. If the driver demands a higher torque the turbocharger will respond by closing the vanes as required. The throttle is closed as this assists in increasing the exhaust gas temperature and reducing the rate of exhaust gas flow, both of which increase the speed at which particulate filter is heated. The exhaust gas recirculation (EGR) valve is closed as the use of EGR lowers exhaust gas temperatures and therefore makes it difficult to achieve the regeneration temperature in the particulate filter. In some models, the glow plugs are sometimes activated to provide additional heat in raising the temperature of the particulate filter. To maintain glow plug serviceability the activation period of the glow plugs is restricted to 40 seconds.

The regeneration process also compensates for ambient temperature changes.

Engine Oil Dilution

A disadvantage of active regeneration is engine oil dilution caused by small amounts of fuel entering the engine crankcase during the post-injection phases. This has made it necessary, in some circumstances, to reduce the oil service intervals. In some cars, the driver of the vehicle is alerted to this by the instrument-cluster message centre.
An algorithm programmed in the ECU DPF module monitors driving style, active regeneration frequency and duration. Using this information the module predicts the level of oil dilution. When the oil dilution level reaches a threshold value (the fuel being 7% of engine oil volume), a red warning lamp and 'Service Required' message is displayed.

Depending on driving style, some vehicles will require an oil change before the standard service interval.

Fuel Consumption

There will be a small increase in fuel consumption due to active regeneration of the particulate filter. During regeneration the fuel consumption approximately doubles. However, because regeneration happens relatively infrequently, the overall increase in fuel consumption is small. This is accounted for in both the instantaneous and average fuel economy displayed in the instrument cluster.



Driver and Dealer Intervention

For drivers who make frequent short journeys at low speeds, it may not be possible to effectively regenerate the particulate filter. In this case, the DPF module will detect a particulate overload condition and a warning message or light will displayed to the driver via the message centre. The driver will be given the opportunity to regenerate the particulate filter by driving the vehicle until the engines normal operating temperature is attained, and then for an additional 20 minutes at a speed of 48 km/h (30 mile/h) or above. Successful regeneration of the filter is indicated to the driver by both the message and warning light being extinguished.

If the message is ignored and no action is taken there is the possibility that the DPF will become blocked. If this occurs the vehicle must be taken to an authorized dealer for the filter to be force regenerated.

NOTE: There is no requirement to manually remove ash or other stubborn compounds during the life of the filter under normal operation.


Diesel Particulate Filter Module

The DPF module monitors and supervises the operation of the DPF system while also monitoring diagnostic data. The DPF module is divided into sub-modules controlled by a coordinator module.
The DPF coordinator module manages the operation of different features when a forced regeneration is requested or cancelled.
The DPF supervisor module is a subsystem of the coordinator module. 
The DPF fuel-management module calculates the timing and quantity of four fuel injections as well as the injection pressure during regeneration.
The DPF air-management module contains the control for EGR, boost pressure, air temperature and pressure in the intake manifold.

In the following, the functionality of each sub-module is explained:

DPF Coordinator Module

The DPF coordinator responds to a regeneration request from the supervisor module by initiating and coordinating the following DPF regeneration specific requests:
EGR cut off
Boost pressure control
Engine  load increase
Control of gas pressure and temperature in the intake manifold
Fuel injection control.

Once a regeneration request is set by the supervisor module the coordinator requests EGR cut off, and regeneration specific boost pressure control. It awaits a feedback signal from the EGR system indicating that the valve is shut. Once this occurs, the coordinator initiates requests to increase engine load by activating electric consumers and controlling the intake air temperature and pressure. Once it receives a confirmation that intake conditions are adequately controlled or expiration of a calibratable time, it switches to a state waiting for an accelerator pedal release manoeuvre from the driver. If this occurs or a calibratable time elapses, the coordinator initiates a request to control fuel injections to increase exhaust gas temperature.

DPF Fuel Management Module

The fuel management module controls: Timing and quantity of four split injections per stroke (pilot, main, and two post injections). Injection pressure and transition between three different levels of injection.
All of which are dependent on the state of the close-coupled catalysts and the state of the particulate filter.
The control injection determines the required injection level as well as an indication of the activity of the close-coupled catalyst and particulate filter.
The injection management calculates the quantity and timing for the four split injections, each for the three calibration levels for injection pressure, and manages the transition between levels.
The two-post injections are required to de-couple the functionality of elevating in-cylinder gas temperature and production of hydrocarbons (to be burnt in the particulate filter). The first post injection is used to generate higher in-cylinder gas temperature and at the same time retain the same torque produced under normal operation mode (non
regeneration mode). The second post is used to generate hydrocarbons which are burnt partly in-cylinder and partly over the close-coupled catalyst, but without producing increased engine torque.


DPF Air Management Module

The DPF air management module consists of:
EGRcontrol
Boost pressure control
Intake air temperature and pressure control.
During regeneration, the EGR feature is shut off, and the closed-loop activation of the boost controller is calculated. The module controls the state of the air in the intake manifold to a predetermined level of pressure and temperature. This is required to achieve correct in-cylinder conditions for a stable and robust combustion of the post-injected fuel.
The module controls the intake air pressure during regeneration by actuating the EGR throttle and adjustment of boost pressure control.

Active Regeneration Protection Limits

For engine and other component protection and durability the DPF module implements some limits during the active regeneration phase, in particular :-
Temperature before the turbocharger inlet must remain below 830 C for turbocharger protection.
Close-coupled catalyst in-brick temperatures must not exceed 800 C and exit temperature must remain below 750*C


I cannot guarentee that all of the above applies to the i30 - but I imagine most of it does.

Now appreciating the complexity of this device serves to explain, in part, why diesels are so much more expensive than petrol engines. For me - it is an added factor in deciding whether my next car is petrol or diesel - I would feel more comfortable without a DPF under the hood that would break the bank if it failed outside warranty.

I am also starting to wonder whether the poor fuel economy of my car is resulting from the DPF regeneration even though I do fairly regular long runs.

I recently found the following post on another car forum which had some snippits of interest

How do they work?
Diesel Particulate filters (DPF) or 'traps' do just that, they catch bits of soot in the exhaust. As with any filter (think of the bag in your vacuum cleaner) they have to be emptied regularly to maintain performance. For a DPF this process is called 'regeneration' – the accumulated soot is burnt off at high temperature to leave only a tiny ash residue. Regeneration may be either passive or active.

Passive regeneration
Passive regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Many cars don't get this sort of use though so manufacturers have to design-in 'active' regeneration where the engine management computer (ECU) takes control of the process.

Active regeneration
When the soot loading in the filter reaches a set limit (about 45%) the ECU can make small adjustments to the fuel injection timing to increase the exhaust temperature and initiate regeneration. If the journey's a bit stop/start the regeneration may not complete and the warning light will illuminate to show that the DPF is partially blocked.

It should be possible to start a complete regeneration and clear the warning light simply by driving for 10 minutes or so at speeds greater than 40mph. If you ignore the light and keep driving in a relatively slow, stop/start pattern soot loading will continue to build up until around 75% when you can expect to see other dashboard warning lights illuminate too. At this point driving at speed alone will not be sufficient and the car will have to go to a dealer for regeneration.

Expensive repairs
If warnings are still ignored and soot loading continues to increase then the most likely outcome will be a new DPF costing around £1000.

Mainly town based driving
If your own car use is mainly town-based, stop/start driving it would be wise to choose petrol rather than risk the hassle of incomplete DPF regeneration.

DPF additives
The most common type of DPF features an integrated oxidising catalytic converter and is located very close to the engine where exhaust gases will still be relatively hot so that passive regeneration is possible. There's not always space close to the engine though so some manufacturers use a different type of DPF which relies on a fuel additive to lower the ignition temperature of the soot particles so that the DPF can be located further from the engine.  The additive is stored in a separate tank and is automatically mixed with the fuel whenever you fill up. Tiny quantities are required though so a litre of additive should treat around 2800 litres of fuel, enough to cover 25,000 miles at 40mpg.  With this type of DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 5 to 10 minutes to complete. You shouldn't notice anything other than perhaps a puff of white smoke from the exhaust when the process is completed.

AA experience
We're seeing some evidence of these systems failing to regenerate too, even on cars used mainly on motorways. It seems that on cars with a very high sixth gear engine revs are too low to generate sufficient exhaust temperature. Occasional harder driving in lower gears should be sufficient to burn off the soot in such cases.

Check the handbook
If you buy a car with a DPF fitted it's important to read the relevant section of the vehicle handbook so that you understand exactly what actions to take if the warning light illuminates and how, if at all, your driving style may need to be adjusted to ensure maximum DPF efficiency and life


AMEN

[neoto]

I must comment on this one:

Active regeneration commences when the particulate loading in the filter reaches a threshold as monitored and determined by the DPF module. This calculation is based on driving style, distance driven and exhaust backpressure signals supplied by the differential pressure sensor. Active regeneration generally occurs approximately every 400 kilometers (250 miles) although this will depend on how the vehicle is driven.

From my log on DPF regenerations, my i30 regenerates DPF every almost exactly 700km, no matter how I drive. In summer, in winter, city, highway, high-load, low-load... nothing matters. It really looks like that Hyundai engineers simply put a distance counter for the regeneration.
During the regeneration, the fuel consumption is higher for about 2-3 l/100km, which in regeneration period affects the fuel consumption by 0.1-0.2 l/100 km.

[baroudeur]

From my log on DPF regenerations, my i30 regenerates DPF every almost exactly 700km, no matter how I drive. In summer, in winter, city, highway, high-load, low-load... nothing matters. It really looks like that Hyundai engineers simply put a distance counter for the regeneration.

How do you know when regeneration occurs?

[Phil №❶]

Great post Alan &

 

Hooray, at last, someone to verify what I've been saying all along.

"The exhaust gas recirculation (EGR) valve is closed as the use of EGR lowers exhaust gas temperatures and therefore makes it difficult to achieve the regeneration temperature in the particulate filter."

Others have stated that blocking EGR lowers Engine temps, sorry that's not correct. EGR blocking raises exhaust temps and this can't be good for your turbo long term IMO. 

[AlanHo]

This control function is made possible by the flexibility of the common-rail fuel injection engine in providing the precise control of: fuel-flow, fuel pressure, and injection timing, all of which are essential requirements for an efficient regeneration process. After-market re-mapping of the ECU or the fitting of plug-in tuning boxes may interfere with this fine balance and lead to premature DPF failure.

This statement caught my eye. I have no doubt that tuning boxes and re-mapping can increase engine power and improve performance - but there is clearly another side to the coin.  I suppose however, that those who re-map or fit tuning boxes are guys who always push their cars hard, thus maintaining high exhaust temperatures. This will possibly avoid the need for forced DPF regeneration - or will it?

[AlanHo]

From my log on DPF regenerations, my i30 regenerates DPF every almost exactly 700km, no matter how I drive. In summer, in winter, city, highway, high-load, low-load... nothing matters. It really looks like that Hyundai engineers simply put a distance counter for the regeneration.

How do you know when regeneration occurs?

 

I have prosted in other threads on the forum the same question - but still don't know the answer. In 13,000 miles of mixed town and urban driving I have never seen a warning light or any other evidence that my DPF is regenerating (and I definitely do have a DPF on my car).  I asked the question of my dealership service manager and he theorised that perhaps I do enough long fast journeys from time to time to avoid the need for regeneration - but on long journeys I drive gently in 6th gear at 60 to 65 mph. I thought this was OK until I read this :-

AA experience
We're seeing some evidence of these systems failing to regenerate too, even on cars used mainly on motorways. It seems that on cars with a very high sixth gear engine revs are too low to generate sufficient exhaust temperature.

[Phil №❶]

From my log on DPF regenerations, my i30 regenerates DPF every almost exactly 700km, no matter how I drive. In summer, in winter, city, highway, high-load, low-load... nothing matters. It really looks like that Hyundai engineers simply put a distance counter for the regeneration.

How do you know when regeneration occurs?

 

I have prosted in other threads on the forum the same question - but still don't know the answer. In 13,000 miles of mixed town and urban driving I have never seen a warning light or any other evidence that my DPF is regenerating (and I definitely do have a DPF on my car).  I asked the question of my dealership service manager and he theorised that perhaps I do enough long fast journeys from time to time to avoid the need for regeneration - but on long journeys I drive gently in 6th gear at 60 to 65 mph. I thought this was OK until I read this :-

AA experience
We're seeing some evidence of these systems failing to regenerate too, even on cars used mainly on motorways. It seems that on cars with a very high sixth gear engine revs are too low to generate sufficient exhaust temperature.

It would appear that you may be completing your regeneration quite effectively as the text above stated :-

"It should be possible to start a complete regeneration and clear the warning light simply by driving for 10 minutes or so at speeds greater than 40mph."

If it wasn't working right, I'm sure you would be able to feel the effects of a blocked DPF by now.

Regarding tuning boxes, thank goodness we don't have DPF on I30's in Australia yet. There has to be a better way

[neoto]

From my log on DPF regenerations, my i30 regenerates DPF every almost exactly 700km, no matter how I drive. In summer, in winter, city, highway, high-load, low-load... nothing matters. It really looks like that Hyundai engineers simply put a distance counter for the regeneration.

How do you know when regeneration occurs?

The most notable:

1. The engine is shaking violently in idle (even more at ~1300 rpm)
2. The fuel consumption is higher by 2-3 l/100 km (if you're driving like a maniac, you would not see the difference at all, but if you're driving economically, this one catches your eyes immediately.
3. The sound of the engine is more 'diesel' like

[AlanHo]

In the 2012 i30 owners manual it states :-

Diesel Particulate Filter (If equipped).

The DPF system removes soot emitted from the vehicle.

Unlike a disposable air filter, the DPF system automatically burns (oxidises) and removes the accumulated soot according to the driving condition. In other words, the active burning by engine control system and high exhaust gas temperature caused by normal/high driving conditions burns and removes the accumulated soot.

However, if the vehicle continues to be driven at low speed for long time, the accumulated soot may not be automatically removed becaause of low exhaust temperature. In this particular case, the amont of soot is out of detection limit, the soot oxidation process by engine control system may not happen and the malfunction indicator light may blink.

When the malfunction indicator light blinks, it may stop blinking by driving the vehicle at more than 60km/h (37 mph) or at more than second grear with 1500-2000 engine rpm for a certain time (about 25 minutes)

If the malfunction indicator light continues to be blinked in spite of the procedure, we recommend that the system be checked by a HYUNDAI authorised repairer.

If you continue to drive with the malfunction light blinking for a long time, the DPF system can be damaged and fuel consumption may worsen.

CAUTION - Diesel fuel

it is recommended to use the regulated automotive diesel fuel for vehicle equipped with the DPF system

If you use diesel fuel including high sulfur (more than 50 ppm sulfur) and unspecified additived, it can cause the DPF system to be damaged and white smoke can be emitted.

FOOTNOTE
I note that you guys in Australia do not have DPF equipped cars - I have therefore written to your wonderful Prime Minister pointing out that she is depriving her citizens of the benefits we enjoy in Europe and is therby missing out on extra tax revenue by the increase in car prices that would result.

You don't have to thank me for my altruistic gesture - just seeing the collective smile on your faces will be reward enough................

[rustynutz]

Curse you, oh evil one! 

[Dazzler]

 

[Phil №❶]

You don't have to thank me for my altruistic gesture - just seeing the collective smile on your faces will be reward enough................

Alan displays his "Dark Side"   

[2i30s]

:

You don't have to thank me for my altruistic gesture - just seeing the collective smile on your faces will be reward enough................

Alan displays his "Dark Side"   

[2i30s]

I'm surprised that a light wasn't fitted to alert you to the fact that there is a regeneration of the dpf occurring. 

[Phil №❶]

I'm surprised that a light wasn't fitted to alert you to the fact that there is a regeneration of the dpf occurring. 

Something all car manufacturers would rather we forget. 

[Asterix]

I'm surprised that a light wasn't fitted to alert you to the fact that there is a regeneration of the dpf occurring. 

I think most carowners would freak out if a light came on in the dashboard. Most owners never read the owners manual, so they would drive straight to the dealer with the light flashing and claim there's an error on the car.

My thought of why there's not a light when regenerating.