Achieving a cumulative 20,000 hours of testing with equipment operators, Cummins says that initial results of its Tier 4 Interim/Stage IIIB field-test program have confirmed up to a 5% higher fuel efficiency and improved productivity over Tier 3-powered commercial equipment. The program entailed the replacment of Cummins' Tier 3 engines with Tier 4 engines with equivalent power ratings, Cummins Particulate Filters (CPF), and new Cummins Direct Flow air cleaners.
According to Cummins, field test operators "expressed a strong preference for [the] Tier 4 Interim repowered machines, as those machines demonstrated improved productivity with faster cycle times." The Tier 4I engines feature a faster power-and-torque response via a variable geometry turbocharger and enhanced fuel systems.
Besides the reduction in overall costs of operations identified by operators, other input included that the Tier 4I repowered equipment offered improved working environment due to quieter running and the elimination of visible smoke. Participants also noted that the Tier 4I system was effectively transparent, with the self-regenerating CPF requiring no user intervention.
"This is the most extensive field test program we have ever undertaken with our off-highway engines," said Hugh Foden, Executive Director, Cummins Off-Highway Business. Logically, Cummins says the previous, most extensive off-highway test program was for Tier 3 engines
"The field test and prototype engine program will continue to expand as we approach a total of 100 Tier 4 Interim installations with our OEM partners. They are able to quickly move ahead with installations, using Cummins' fast-track machine integration process specifically developed for EPA Tier 4 Interim and EU Stage IIIB applications."
The Cummins field test program is structured to capture a broad range of duty cycles, applications, and different working environments. All the Tier 4I repower and cooling modification work has been undertaken on-site, using Cummins machine integration process. The replacement of the Tier 3 exhaust muffler with the CPF aftertreatment represents the most significant installation change. The new air cleaner has a smaller space claim and has proved beneficial in extending filter change intervals.
Tier 4I system performance is monitored over a cellular network with remote downloads directly from the engine's electronic control module to the field test team.
"Remote monitoring is an invaluable method for rapidly collecting operational data for analysis, but regular site visits to the field test locations are equally important so we can listen to the customers and capture their working experience," said Maged Tadros, Cummins Tier 4 Field Test Program Leader.
Tadros said that "the field test machines proved that most off-highway equipment operates at a high enough engine load factor for the CPF to self-regenerate almost every time in passive mode."
Active self-regeneration typically occurred less than 1% of operating time, "with the machine continuing to operate as normal during the regeneration," said Cummins, adding that the fuel consumed to activate the self-regeneration process was barely measurable.
Service intervals and procedures for the Tier 4I engines remain nearly identical to those for Tier 3 engines. The CPF exhaust aftertreatment is service-free up to 5000 h, when an ash-cleaning service is required.
The Tier 4I repowered equipment on the field tests typically achieved 98 or 99% uptime, equivalent to Tier 3 levels of in-service reliability.