Back in 2011, Cummins began research into smaller, more efficient diesel engines, and three years later, the government-backed project has made significant progress. Cummins reports that its downsized T2B2 delivers 40% better fuel economy than comparable gasoline V8s, surpassing expectations.
The $30 million project got half its money from the U.S. Department of Energy, giving Cummins and its partners Nissan and Johnson Matthey the funds to make significant advancements in diesel fuel efficiency. The core of this project is the 2.8 liter T2B2 engine, which delivers equivalent power but much better fuel economy compared to conventional gas V8s, which dominate the U.S. truck market. Green Car Congress reports that these improvements include;
- Replacing the aluminium V8 gasoline engine and emission control system with smaller diesel (2.8-liter) and its emission control system (ECS) without a weight penalty. Cummins made extensive use of aluminium as well as space-saving design features for new engine weight control. The aluminum block and head is sandwiched between an iron backbone cam carrier and iron ladder frame base, firmly held with iron-to-iron bolts.
- Lightweight steel pistons provide reduced friction & compression height with increased power density.
- Cummins achieved its weight-neutral goal based on a gasoline engine with emission control system (ECS) weight of 514 lbs (233 kg); the new aluminum 2.8L diesel weighs 362 lbs (164 kg), while the ECS weighs 152 lbs (69 kg).
- Taking learnings from LTD and LDECC programs to utilize PCCI (pre-mixed charge compression ignition) and high charge flow operation.
- Low pressure EGR; Johnson Matthey’s Cold Start Concept (CSC) catalyst for cold start NOx & HC mitigation; an NH3 gas system from Amminex for immediate reductant delivery; and a small engine running higher loads resulting in faster warm-up all contribute to reducing the fuel economy penalty for meeting the more stringent emissions target.
Though the project initially only aimed for a 26 MPG combined rating, internal targets are much higher, and the results are progressing at an impressive clip. Nissan has already committed to a Cummins diesel for the Titan full-size pickup, though they also teased us with a diesel-powered Frontier mid-sized truck. There could be more diesel Nissans on the way as a way to compete in a truck market still dominated by domestic manufacturers.