You probably don’t want a chemistry lesson now any more than you wanted one in high school, but a little chemistry will help you understand the emission system on your Komatsu equipment and why you might be having problems. Emissions regulations are designed to eliminate the particulate matter created by an internal combustion engine—basically soot and NOx, or nitrogen oxides.
“Komatsu uses a process called regeneration in the Diesel Particulate Filter (DPF) to break the soot down into basic carbon molecules that are not harmful to the air. The DPF produces a chemical reaction using a catalyst,” explained Mike Montgomery, trainer for Columbus Equipment Company.
For the process to work, three things must be present: catalyst, soot and heat (480 degrees F or higher). On a Komatsu engine, the heat comes from exhaust, and once the exhaust gets that hot, regeneration happens continuously and automatically. This is referred to as passive regeneration.
The machine can also perform active regeneration by adding fuel to the process to increase the heat and accelerate catalyzing the soot. A Komatsu will go into active regen mode when soot buildup in the DPF filter reaches a certain point. The machine also has an internal clock and it will perform active regeneration after 24 to 26 hours of operation.
However, machines used in light-duty applications may not achieve a 480-degree heat point, so the required level of passive regen will not be performed. In these situations, the machine will actively regenerate more often. Small problems like a mass air flow sensor screen that’s blocked or a leak in the boost line may also cause the machine to perform active regen more often. Fixing these small problems usually fixes the issue of excessive active regeneration, Montgomery said.
Whatever your application—light or heavy—it’s important to understand the machine will regen most efficiently when it is working, or in the proper idle position. The “proper idle position” is achieved in a wheeled machine with the park brake on, and no throttle … and with lock levers in the locked position, and fuel dial at minimum in a track machine. Bottom line: Efficient regeneration results in longer DPF life, and more efficient operation.
In future issues, Mike will review proper idle position and DEF storage protocols.