The latest from Myers Equipment and Thomas Built Buses

July 2017



By now, everyone in the school bus industry is familiar with the Cummins engine.  However, what you may not be familiar with are the recent improvements to the engine and the aftertreatment system. Though Cummins is the only current diesel option available in the Type C and D school bus market, they are continuously making improvements, many of which have been in place since the start of 2017.

On the engine itself, Cummins has tweaked and improved the combustion recipe, which means better fuel economy for your fleet. This will further bridge the gap between diesel and other types of fuel, in terms of MPG or MPGE (miles per gallon equivalent). They have also reduced the amount of friction within the power cylinder and enhanced turbo efficiency, which add up to improved performance.

The after-treatment system has been completely redesigned. The old three module system has been simplified and is now a single module after- treatment system. This translates to a 33% reduction in size, a 15% reduction in weight, and increased overall efficiency. The DEF dosing system has been improved, as well. Now, it provides more efficient atomization and minimizes deposit formation. What does that mean in English? It means that when deposit formation is reduced, your Diesel Particulate Filter will not load up as quickly.

Another move that will help the DPF do its job more effectively is a complete shift in Exhaust Gas Recirculation strategy.  Now, Cummins uses 30% less EGR. Naturally, the less EGR that you use, the less “recirculated” air that is in the system. When exhaust gas recirculates, the dirty air is put back into the system. This is why we have seen extensive problems with systems that relied heavily on EGR in the past.

Finally, Thomas has approved the use of the “Stay Warm” Passive Regen Control. This simple parameter change enables the system to passively regen more often. It is better suited to school bus applications (low speed, start and stop). More regens equals less DPF clogging and less headaches for you, your drivers, and your mechanics.

All of these improvements add up to make a great fuel choice even better.  It’s no wonder that diesel makes up over 90% of the market. These latest steps by Cummins and Thomas mean that you can be more confident in diesel than ever before.



Posted in: General, Myers Equipment Monthly, Thomas