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Cummins and Tula study of Diesel Dynamic Skip Fire (dDSF) shows 74% reduction in NOx, 5% in CO2 on low load cycle

Cummins Inc. and Tula Technology, Inc., a leader in propulsion efficiency, announced at SAE International’s WCX the results of their collaborative study on the effectiveness of Tula’s diesel Dynamic Skip Fire (dDSF) in reducing nitrogen oxides (NOx) and carbon dioxide (CO2) emissions on a Cummins X15 HD Efficiency Series diesel engine. (Earlier post.)


Cummins’ X15 Efficiency Series 6-cylinder diesel engine enhanced with Tula’s diesel Dynamic Skip Fire (dDSF)

Dynamic Skip Fire is an advanced cylinder deactivation control strategy that makes decisions for an engine’s cylinders on an individual basis to best meet torque demands while saving fuel and maintaining performance. Tula’s original Dynamic Skip Fire (DSF) software has been shown to significantly reduce CO2 emissions in gasoline engines and has been in production since 2018 with more than one million vehicles on the road. dDSF is the Dynamic Skip Fire application for diesel engines.


Illustration of DSF-affected functions. Srinivasan et al.

Low-load cycle performance was estimated with a well-calibrated powertrain simulation tool to capture accurately the low-load system operation and emissions. This system showed a 74% reduction in NOx and a 5% reduction in CO2 compared with today’s clean diesel technologies.

In comparison with current engine technologies and modifications to the thermal management techniques, dDSF saved 20% in fuel, validating dDSF as a more fuel-efficient means of reducing NOx.

Cummins and Tula demonstrated the positive dDSF results in a Class 8 truck powered by a Cummins X15 HD engine. The dDSF test results highlight a promising technical advancement for an industry seeking strategies to address future, more stringent NOx emissions regulations for diesel engines.


  • Srinivasan, V., Wolk, B., Cai, X., Henrichsen, L. et al. (2021) “Application of Dynamic Skip Fire for NOx and CO2 Emissions Reduction of Diesel Powertrains,” SAE Technical Paper 2021-01-0450, doi: 10.4271/2021-01-0450.


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