Cummins Inc. has debuted to the North American agricultural market the new QSG12, with up to 512 hp (382 kW) output for heavy-duty applications, at the World Ag Expo. The 6-cylinder, 12-liter engine is purpose-designed to meet U.S. Environmental Protection Agency (EPA) Tier 4 Final near-zero emissions regulations, with a more compact envelope and over 30% higher power-to-weight ratio than the class average for engines with a similar power range.
The new QSG12 brings a major advantage for Tier 4 Final/Stage IV equipment installations, as 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.
With ratings covering a broad 335 to 512 hp (250 to 382 kW) range, the QSG12 offers an ideal power solution for a wide variety of demanding agricultural applications, from large tractor and combine, forage and vegetable harvesters to forestry applications and large irrigation sets.
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 1,900 lbs. (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 QSG12 sets a new benchmark for heavy-duty engines with its ability to outperform any comparable engine, yet provides a smaller, lighter and simpler engine package to install," says Nishant Prabhu, General Manager - Cummins Agriculture Business. "The new QSG12 provides an ideal opportunity for agricultural equipment manufacturers to downsize to a far more productive and economic 12-liter engine with all the heavy-duty durability and performance they need," adds Prabhu.
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/Stage IV 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 engine.
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 1,700 lbs.-ft. (2,305 Nm), together with a torque rise as high as 60% available. These attributes enable the QSG12 to deliver exceptionally fast response to increasing load factors from low engine rpm, allowing for favorable lugging ability.
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% 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 is a next-generation design with a copper zeolite-based catalyst capable of over 95% 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 AdBlue(R)/Diesel Exhaust Fluid (DEF) dosing levels are minimized due to a high-precision injection spray pattern with more effective fluid decomposition.
When the cost of AdBlue/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/Stage IV remains lower than that of the previous QSX11.9 engine at Tier 4 Interim/Stage IIIB.
Cummins Emission Solutions experience of integrating DPF and SCR technology as a single system is unmatched in the industry, with almost 500,000 Cummins engines produced with the combined aftertreatment.
Built For Extremes
The Cummins QSG12 is built ready to deal with the toughest operational extremes experienced by agricultural machinery. 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, and is designed with durability equivalent to that of the engine. 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/Stage IV applications. The Direct Flow air filter provides greater dust-holding capacity in a smaller package, with filter element change intervals at least twice those 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% of 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.
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 Front Power Take-Off (FEPTO), with up to 464 lbs.-ft. (630 Nm); Rear Power Take-Off (REPTO)/hydraulic drive, with up to 516 lbs.-ft. (700 Nm); 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.