Regeneration is a combustion process that destroys engine exhaust products and pollutants that may have accumulated in the exhaust filter, the DPF. It occurs in diesel engines that are fitted with a Diesel Particulate Filter, DPF, where the engine generates extremely high temperatures to combust the accumulated by-products.
Modern tractors are fitted with highly efficient engines and exhaust systems that are designed to comply with environmental regulations for clean emissions. The engines come with the DPF that filters all toxic gases and solid matter (particulates) to ensure minimal toxic emissions into the environment.
Over time, the DPF becomes filled up with toxic waste and particulates which must be cleaned/removed to enable the device to continue capturing these particulates. This cleaning process is called regeneration.
In this article, we shall briefly explain the regeneration process in an LS tractor before looking at regeneration problems, symptoms, and how to fix these problems whenever they arise.
The LS Tractor Engine
The LS tractor has a Tier 4 engine reputed for its high output and incredible fuel efficiency. Being a Tier 4 engine means the engine meets the environmental standards on emissions. It is equipped with a DPF and an EGR (electronic Exhaust Recirculation Device) that greatly reduces solid and gaseous emissions as well as operating with very low vibrations and low noise levels.
Like any other diesel engine fitted with a DPF, the LS tractor engine must undergo regular DPF regeneration procedures. There are two main regeneration procedures -active and passive. When the DPF becomes clogged with particulate matter (soot), a dashboard light will come on to warn the operator that the regeneration process is required to clean the DPF.
The LS tractor has three indicator lights related to the DPF-DPF Regeneration Indicator 1, DPF Temperature Indicator 2, and DPF engine warning Indicator 3.
LS Regeneration Process
1) Active/Auto Regeneration
Auto regeneration occurs when the operator does not take any action (when the DPF regeneration light 1 illuminate). The regeneration process is activated automatically. During the auto/active regeneration, the tractor continues in its operations while the engine activates the regeneration process. The whole regeneration process is controlled by the tractor engine's Electronic Controller Unit, ECU. The process happens as follows:
- When the soot load in the DPF reaches 60%, the regeneration indicator light (1) will come on
- If the operator fails to take any action, the ECU activates the auto-regeneration process
- The engine generates extremely high temperatures to burn the soot in the DPF until it oxidizes into carbon dioxide.
- The tractor engine must continue operating at an RPM above 1800 during the regeneration process, for approximately 30-40 minutes to ensure the whole process is completed
- During the process, the DPF regeneration light and the DPF temperature light will both be ON automatically.
- The process must not be interrupted until all regeneration-related lights go off, indicating that the DPF is now clean.
2) Passive/Forced Regeneration
This type of regeneration is activated by the operator. When the DPF warning light comes on, the operator puts the auto regeneration on hold by pressing the inhibition switch. This means the regeneration is put on hold until the operator is ready to start it, but it should be as soon as possible.
Note that if the DPF Engine warning indicator light (3) comes on, the regeneration process should be started at the earliest opportunity as the soot load in the DPF is too high at that point. To initiate the process,
- Stop the tractor and park it on level ground. Park the tractor in a safe place outdoors, away from any flammable/combustible materials.
- If the tractor was in a heavy-duty operation, let it cool down for five minutes
- Press the regeneration button/switch
- Let the process run uninterrupted until it is over.
- During the forced regeneration, the ECU pumps extra fuel into the exhaust regeneration 'burner' to raise the temperatures to the desired levels.
- After the process is complete, the fuel pump will run for some time to cool down the system. Let it run until it is cool to avoid receiving error messages.
Problems Associated with LS Tractor Regeneration
It is not every time that the regeneration process passes without a mishap. Sometimes, the process may fail to materialize or may bring up other issues that may affect the operations, reliability, or output of the LS tractor. Here are some of the major issues you may experience with the regeneration processes.
1) Failure to Complete a Regeneration Process
If a regeneration process fails to complete, the DPF regeneration light will remain on and may be accompanied by an annoying continuous dashboard alarm. This failure can arise from-
- Sensor failure- the soot accumulation pressure sensors may fail to detect the soot levels. Thus, the regeneration process cycles are interrupted or become unreliable.
- Short drives/distances- The active regeneration process requires a longer drive at a certain speed for the process to complete. If this is not achieved, the regen process will be incomplete.
- An interruption or the engine failing to acquire the requisite temperatures due to a low RPM or speed.
An incomplete regeneration process may lead to a clogged DPF leading to an increase in fuel consumption, engine inefficiency, or even engine seizure.
Solution:
- Ensure that you have regular maintenance service on the exhaust system to keep the sensors active. This ensures the DPF soot load is detected at the right levels for cleaning.
- During an active regeneration, ensure you maintain the required engine speed for the entire duration of the regeneration process.
2) Dirty/Clogged DPF
If your DPF is very dirty or clogged with soot, the regeneration process may fail to initiate. Ash accumulation which is not properly combusted during the regeneration process builds up in the filter. This damages and shortens the lifespan of the DPF. Thus the regeneration process will not initiate.
Moreover, accumulation of soot and ash in the DPF reduces exhaust gas pressure which reduces the effectiveness of the engine. A clogged DPF also obstructs air circulation within the exhaust system.
Solution:
- Ensure you carry out regular checks and cleaning of the DPF as per the LS tractor manual. Cleaning removes ash residue that builds up over time or when the regeneration process fails to complete.
- Physically remove any debris that may be visible as recommended by the tractor user manual
- Apply cleaning chemicals to remove any stubborn ash residue in the filter
- When the DPF reaches its end, or when it becomes damaged, replace it immediately to avoid regeneration issues.
3) Insufficient oil
The regeneration process may fail to initiate if the engine has insufficient oil. Oil is necessary for the process of cooling the engine due to the heat generated during regeneration. Moreover, the recommended type of oil must be used at all times.
Solution:
- Top up the oil to the recommended maximum level (Note that regeneration will not begin if the oil is less than 25% of the maximum engine capacity.
- Use high-quality engine oil which will not only support the regeneration process but will also prolong your engine life.
4) DPF Not Getting Hot Enough
The DPF must reach a certain temperature (over 6000 C) for the soot to be oxidized into a gas/vapor for eventual removal. The thermal process oxidizes the solids (soot) into carbon dioxide. The heat is generated by the engine and channeled through the exhaust system to the DPF. This failure could be caused by:
- A clogged exhaust system that is unable to channel the heat to the DPF burner.
- A problematic engine control system that is unable to manage the heat to the required level.
- An air filter may restrict air flow, thus restricting the combustion process that generates heat.
- Faulty sensors which interrupt the regeneration cycles
Solution:
Have the DPF and the exhaust system diagnosed by a qualified technician who will recommend and carry out the required repairs. If this is not done, it may lead to more critical and expensive damage to the tractor engine.
5) Other Problems and Symptoms
- Diluted Engine Oil- When regeneration fails or is interrupted, the extra fuel that had been input into the cylinders is drained into the engine oil sump. This dilutes the engine oil and affects the quality of the lubrication process in the engine.
- Loss of engine Power- you realize that your LS tractor is progressively losing engine power without any symptoms of engine malfunction
- Hard Start- it becomes increasing hard for the engine to crank into life when started
- Visible Exhaust Gases- With a properly functioning DPF (and EGR), there should be no visible exhaust gases from the exhaust pipe. Any visible gas/or odor could be a sign of a failing DPF.
- Persistent Error Messages-if you continuously get error messages, it is a sign that there is an imminent critical failure in the LS tractor that is about to occur.
Although these symptoms may not necessarily point to a DPF regeneration-related issue, they are more likely to arise from failed regenerations. The exhaust system is as important as the internal workings of the tractor engine and any issue relating to clogging or failure of the DPF automatically affects the engine performance and output.
