The new QSG12 brings a major advantage for Tier 4 Final and Stage IV equipment installations by restoring the envelope size of the QSM11 predecessor, used for Tier 3 and Stage IIIA applications. Higher efficiency air handling and advanced combustion enable the QSG12 to return to the simplicity of a wastegated turbocharger and achieve near-zero emissions without the need for a cooled Exhaust Gas Recirculation (EGR) system. As a result, internal loads on the QSG12 are reduced to free up extra power potential, while heat rejection is lowered by over 40 percent compared with engines using cooled EGR.
A key design focus for the QSG12 has been to achieve significant weight savings in order to increase the power-to-weight ratio. A sculptured block retains high rigidity while removing unnecessary mass. The use of composite material for the oil pan and valve cover provides further weight savings. With this innovative approach, the QSG12 achieves a remarkably low engine weight of just 1900 lb (862 kg) to enable a top-rated power-to-weight ratio of 0.27 hp per lb (0.44 kW per kg) while retaining all the structural strength and durability expected of a Cummins heavy-duty engine.
The G Series offers fuel efficiency through parasitic reducing technology without variable-flow pumps that add unnecessary cost and reduce reliability. Its Single Cam In Head (SCIH) design with roller valve train and high-efficiency intake ports continues the design theme of minimum complexity and maximum efficiency. The resulting low-weight design allows more payload to be delivered while requiring less energy to manufacture than competitive designs.
With ratings covering a broad 335 hp to 512 hp (250-382 kW) range, the QSG12 offers an ideal power solution for a wide variety of applications, including wheel loaders, excavators, cranes and material handling, road building equipment, compressors, screening and crushing machines.
Xtra-High Pressure Advantage
The QSG12 incorporates Cummins Xtra-High Pressure Injection (XPI) fuel system, derived from the larger and more powerful QSX15 Tier 4 Final engine. Although scaled down in size for the 12-liter platform, the XPI fuel system retains all the robust, heavy-duty characteristics of the system, proven up to 675 hp (503 kW) on the 15-liter.
With multiple injection events driven by high-precision Cummins electronic controls, the XPI fuel system contributes to a very impressive peak torque for the QSG12 of 1700 lb-ft (2305 N•m), together with a torque rise as high as 60 percent available. These attributes enable the QSG12 to deliver exceptionally fast response to increasing load factors from low engine rpm.
XPI plays a significant role in enhancing engine sociability, with lower noise, less vibration and smoother power delivery. The use of a rear gear train also contributes to overall engine refinement by reducing vibration and lowering noise by at least 1 dBA.
Ultra-Clean DPF-SCR Aftertreatment
The QSG12 is designed as a fully integrated air intake to exhaust aftertreatment package ready for drop-in machine integration. Designed and manufactured for the 12-liter engine by Cummins Emission Solutions (CES), the aftertreatment combines a Diesel Particulate Filter (DPF) with Selective Catalytic Reduction (SCR) to achieve an ultra-clean exhaust.
Based on Cummins Tier 4 Interim/Stage IIIB experience, the DPF operates as a near passive device, with automatic active regeneration occurring less than 1 percent of engine running time. The use of a DPF in the exhaust stream provides the QSG12 with an additional margin of Particulate Matter (PM) emissions control at higher engine loads, to realize better transient response. The heavy-duty DPF has no impact on equipment operation, with the machine continuing to work as normal during automatic active regeneration.
The SCR system developed by Cummins for Tier 4 Final/Stage IV is a next-generation design with a copper zeolite-based catalyst capable of over 95 percent conversion of Oxides of Nitrogen (NOx), able to operate more efficiently at lower temperatures, with advanced sensors providing full closed-loop control. Using an Ecofit™ UL2 doser supplied by CES, the Diesel Exhaust Fluid (DEF)/AdBlue dosing levels are minimized due to a high precision injection spray pattern with more effective fluid decomposition.
When the cost of DEF required for the SCR system is combined with the cost of fuel consumed, the overall fluid operating cost of the QSG12 for Tier 4 Final remains lower than that of the previous QSX11.9 engine at Tier 4 Interim.
Cummins Emission Solutions experience of integrating DPF and SCR technology as a single system is unmatched in the industry, with almost 450,000 Cummins engines produced with this combined aftertreatment.
Built For Extremes
The QSG12 is built ready to deal with the toughest operational extremes experienced by off-highway machines. Even working under high load factors, the QSG12 will achieve the same legendary life-to-overhaul as that achieved by the QSM11 at Tier 3 and Stage IIIA. Operators of QSG12-powered machines can expect – and may exceed – 12,000 hours before overhaul. Significantly, no midlife engine overhaul is required.
Cummins DPF-SCR aftertreatment system is able to withstand severe shock loads and vibration, designed with durability equivalent to that of the engine. Additionally, the QSG12 can work at 45-degree angularity with just the standard oil sump fitted.
To provide maximum engine protection, particularly when working under dusty conditions, the QSG12 features an integrated Cummins Direct Flow™ air filtration system developed for Tier 4 applications. The Direct Flow air filter provides greater dust-holding capacity in a smaller package, with filter element change intervals at least twice that of conventional air filters. The filter also features an embedded smart sensor to fully integrate air-intake flow with the engine combustion.
A two-stage fuel filter system for the QSG12 features the latest NanoNet™ media from Cummins Filtration, to ensure that the XPI fuel injection system is fully protected against fuel contaminated with hard particles. NanoNet media trap almost 99 percent of all particles as small as 5 microns, so that the filter works more effectively for longer, with less fuel-flow restriction.
Cummins Filtration’s expertise also extends to a high-efficiency coalescing filter, for eliminating crankcase hydrocarbon emissions and oil mist, further adding to the clean-engine credentials of the QSG12.
Machine-Adaptive Features
The QSG12 is specially configured with an array of machine-adaptive features to facilitate machine integration across a diverse range of applications. For example, the Cummins wastegated turbocharger is available in either a rear-out, low-mount position or in a front-out, mid-mount position, to provide added installation flexibility.
Other useful options include a front power take-off (FEPTO) with up to 564 lb-ft (630 N•m), a rear power take-off/hydraulic drive (REPTO) with up to 516 lb-ft (700 N•m) and a side-mounted drive for a hydraulic pump. For machines requiring engine braking, a compression brake option is available, or an integral exhaust throttle can be utilized.
The DPF-SCR ultra-clean aftertreatment system used by the QSG12 easily adapts to each specific machine installation space, due to a modular format enabling multiple configurations in both horizontal and vertical orientations.
The QSG12 medium-bore engine fully complements that of the QSX15 big-bore engine, to extend Cummins heavy-duty power range up to 675 hp (503 kW) for Tier 4 Final/Stage IV, with both engines sharing similar DPF-SCR aftertreatment technology.
