Evaluation of Cylinder Deactivation on a Class 8 Truck over Light Load Cycles

Selective Catalytic Reduction (SCR) systems provide excellent NO_X control for diesel engines provided the exhaust aftertreatment inlet temperature remains at 200° C or higher. Since diesel engines run lean, extended light load operation typically causes exhaust temperatures to fall below 200^° C and SCR conversion efficiency diminishes. Heated urea dosing systems are being developed to allow dosing below 190° C. However, catalyst face plugging remains a concern. Close coupled SCR systems and lower temperature formulation of SCR systems are also being developed, which add additional expense. Current strategies of post fuel injection and retarded injection timing increases fuel consumption. One viable keep-warm strategy examined in this paper is cylinder deactivation (CDA) which can increase exhaust temperature and reduce fuel consumption. Cycles such as the heavy-duty federal test procedure (HD FTP) which have long idle periods can benefit from CDA by increasing temperature, lowering exhaust flow, and reducing catalyst cooling. This technology could become even more important if future regulations include low load cycles. For this paper, CDA was utilized at loads below 6 bar brake mean effective pressure (BMEP) over multiple transient low load cycles and other standard cycles. The test platform was a 2018 13L class 8 engine with production aftertreatment system and lost-motion CDA system. Results showed up to a 50° C exhaust temperature increase, which allows for high NO_X conversion efficiencies across the SCR as compared to baseline operation. There is also a reduction in CO₂ emissions up to 15 percent.