Compact Power from Cummins QSF3.8
Cummins new QSF3.8 3.8-liter engine redefines the meaning of four-cylinder compact power by delivering a combination of performance and durability with economic operation.
The QSF3.8 simplifies Tier 4 Final integration in a wide range of ag equipment, meeting near-zero emissions standards with a selective catalytic reduction (SCR)-only after treatment system. With particulate matter reduction focused in-cylinder, the QSF3.8 avoids the need for either a diesel oxidation catalyst (DOC) or a diesel particulate filter (DPF).
The SCR-only system features a high-efficiency catalyst able to convert oxides of NOx emissions at lower exhaust temperatures while requiring only low-dosing levels of diesel exhaust fluid (DEF).
The higher efficiency of the SCR aftertreatment reduces the amount of cooled exhaust gas being recalculated by the engine, with a corresponding reduction in engine loading and cooling demand. The lighter-flow exhaust gas recirculation (EGR) enables the performance potential of the QSF3.8 to be fully realized. Peak torque of 360 pound-foot is delivered by the Cummins wastegated turbocharger.
“We took on the challenge of introducing the 3.8-liter engine with the simplest and smallest aftertreatment solution we could develop, and our SCR-only approach has succeeded in creating that advantage for increasingly space-constrained equipment,” says Nishant Prabhu, Cummins.
Smaller Meets Stronger
The QSF3.8 is built with strength at the heart of the engine and is capable of the same peak cylinder pressure as the larger Cummins QSB4.5. This means that the QSF3.8 is designed to operate at relaxed ease, resulting in higher in-service reliability and engine durability.
The QSF3.8 takes a design lead from the Cummins QSB4.5 engine by featuring a rear gear train, providing improved mounting stiffness and lower gear noise. The high-strength cast-iron block has a sculpted design, allowing unnecessary weight to be removed while retaining maximum rigidity. The use of composite material for the valve cover and oil pan brings a further weight reduction.
Less to Service
Servicing is made simpler through remote mounting of the Electronic Control Module (ECM), for easy plug-in diagnostics and data downloads. The oil, lube filter, and fuel filter are set up for rapid service, with 500-hour intervals.
The QSF3.8 features the Cummins Direct Flow air filtration system, which provides greater dust-holding capacity in a smaller package, and has a filter element change interval at least twice that of a conventional air filter. The engine is equipped with a robust High Pressure Common Rail fuel system driven by Cummins full-authority electronic controls.
To protect the fuel injectors against fuel contaminated with hard particles, a two-stage fuel filter system with Cummins latest NanoNet media traps almost 99% of all particles.
The engine lubricating pump is driven by the crankshaft rather than driven by gear from the camshaft – an approach that benefits the design through its simplicity and packaging. Noise is reduced, and oil flow is improved during cold starts. A compact cooling module on the engine brings together the water pump, oil filter, and oil cooler, leading to improved pressure management and better reliability.