Thomas Built Buses announced it now offers standard on all new diesel-powered school buses with standard exhaust configurations and particulate filter temperature stabilization solution from Cummins that resolves active regeneration issues experienced by customers.
The new Thomas school buses with the Cummins solution, also referred to as a “Stay Warm” feature, rolled off the assembly line on April 11.
“Diesel is now one of the cleanest fuels available today. Yet, one of the results of diesel running so cleanly is that in some instances engines may not regenerate frequently enough in order to properly clean out the diesel particulate filter. This lack of regeneration frequency leads to the need for more frequent service cycles today,” said Caley Edgerly, president and CEO of Thomas Built Buses, in a statement on Wednesday.
Mario DiFoggio, manager of Thomas’ Center for Education and Marketing, explained that because today’s clean diesel emissions technology was developed for over-the-road trucks, school buses often do not travel the required road speeds or mileage necessary to trigger regeneration events that properly dose the DPF and clean the filter. Cummins says the optimum speed to initiate regeneration is 40 mph. Regeneration aborts when the vehicle drops below the minimum speed threshhold, as school buses with frequent stops and navigating urban and suburban roads are apt to do. As a result, a growing number of diesel school bus operators have experienced DPF clogging issues and costly equipment break downs that require the buses to be removed from service.
However, the Cummins solution reprograms the engine to only pause regeneration when the vehicle drops below 40 mph to speeds as slow as 5 mph. Regeneration aborts if the school bus remains below the minimum speed threshhold for an "extended period of time," according to Cummins.
DiFoggio added that Thomas dealers in Indiana and Virginia have already validated that the new settings have resulted in proper regen cycles and have reversed any issues with clogged DPFs.
In addition to coming standard on new Thomas school buses, the Stay Warm feature can also be reprogrammed on any model-year 2010 or newer Thomas diesel bus.
“Through significant testing, we have determined that we can optimize the DPF parameters, which helps improve the frequency of the regeneration without affecting the cleanliness of clean diesel,” Edgerly added. “Through this exciting development in clean diesel, fleets will see significant improvement in their engine and DPF performance along with reduced engine maintenance, maintenance costs and fleet downtime.”
DiFoggio said the OEM has been aware of the Cummins DPF temperature stabilization for some time, but parent company Daimler Trucks North America first required the extensive testing before approving the technology from the factory, not only in terms of the peformance but also to ensure the safety of students while loading or unloading the bus.