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Trucks: Engine Health, After-treatment and Face Plugging

October 19, 2017

Over the last two decades, government-driven emissions controls regulations have pushed the private sector to develop some extremely sophisticated systems to achieve emissions goals. Both on- & off-highway applications have achieved over 90% reductions in emissions since the mid-1990s.


The engineered solutions work well enough for most applications, but there are some arenas still suffering perennial problems. These arenas include fleets that operate in heavy-idle situations as well as fleets that operate in extreme climates.


The first group includes operators that sit in standby mode awaiting work (i.e. mining, concrete mixers, etc.). It might also include a delivery truck that rarely works hard, usually idling while the driver is making the delivery, and otherwise travelling short distances between stops.


The extreme climate group often includes vehicles that start their days inside a shop or with block heaters. The engines are turned on all day, even when not being used for hours, the fear being that the engine will not be able to restarted if turned off.


They also often remain on to provide some heat to the drivers. In these cases, the vehicles become strong candidates for the phenomenon known as face plugging. Face plugging is symptomatic of engine/exhaust issues and it consists of black deposits that form as the result of unburnt fuel collecting on the front end of the diesel oxidation catalyst. Oftentimes the issues cascade to the DPF and SCR.


At the same time, there may be similar erosive issues taking place in the engine itself. As seen on page 21 of a Cummins presentation available in diesel.org (http://diesel.org/cms/wp-content/uploads/David-McNeill.pdf), face plugging is often the symptom of:

  • Coolant entering the exhaust system

  • Light duty cycles

  • Low exhaust temperatures

  • Combustion malfunction creating excessive engine smoke

The first issue can only be addressed by reviewing and remediating the head gasket or the cylinder head itself. The other three issues are generally the result of a frequently-underloaded engine running below its optimal operating temperature.


Page 22 of the same presentation reveals what can happen further down the line in the after-treatment system.

DOC Melted (Symptom - Incomplete Stationary Regens)

  • Melted channels prevent exhaust flow

  • Caused by excessive fuel or oil in exhaust

  • When occurring, DPF likely damaged also

What’s a user to do when the job requires operating the engine in a frequent idle existence and/or in extreme climates? Frequent maintenance and regens work to reduce the issues. Another possible solution…..the Ventech LHG.


The LHG does not help the engine to start, but once started, the LHG can do much to benefit the system. It helps to load the engine. A worked engine gets to its ideal operating temperature more quickly, providing for cleaner burning. It elevates exhaust gas temps as well. Finally, the work being done on the LHG converts the engine’s mechani