Cummins B4.5 and B6.7

The Cummins B4.5 and B6.7 are inline four and six cylinder diesel engines available for light-duty trucks, school buses, shuttle buses, and urban transit buses. The engines have a displacement of either 4.5 litres (B4.5) or 6.7 litres (B6.7). The B6.7 was introduced at the National Truck Equipment Association Work Truck Show in March 2016 and available beginning in 2017. The European B4.5 and B6.7 were introduced at the 2016 Euro Bus Expo. They are also available beginning in 2017. These engines are the successor to the ISB4.5 and ISB6.7.

New for Cummins' 2017 line of engines is a Single Module aftertreatment system which combines the Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) and Selective Catalytic Reduction (SCR) systems into a single canister. The more compact, lighter emissions control systems, according to Cummins, also boast greater thermal efficiency for improved engine operation.

The North American B6.7 features enhanced on-board diagnostics (OBD) that ensure emissions stay within the EPA limits as well as enhanced electronic controls. Cummins has also added a particulate matter sensor. The engine meets EPA 2016 and GHG 2017 regulations. It boats a seven percent improvement in fuel economy over the 2013 ISB. The European B4.5 and B6.7 also features enhanced electronic controls. The engines meet Euro 6 Phase-C regulations.

Euro 6 Phase-D requires reduced NOx emissions during lower speed city operations, as well as under cold engine start conditions. On-road testing and real-world measurement are also required. Cummins boasts a 25 percent reduction in NOx emissions, compared to the Euro 6 Phase-A engines introduced in 2015. Refined software and electronics have achieved this reduction.

Improvements to emissions and on-board diagnostics allow the B6.7 to meet the EPA’s 2021 greenhouse gas emission requirements. Maintenance intervals were also synchronized and extended for the 2021 B6.7.

In 2022, Cummins announced their fuel agnostic powertrain strategy. The engines will use blocks and core components that share common architectures and will be optimized for different low-carbon fuels. Component similarity below the head gasket will allow for Cummins to lower production costs and make maintenance easier, while the engine build from the head gasket up will be dependent on the fuel type. Under this strategy, Cummins announced a hydrogen-fueled B6.7 and gasoline-fueled B6.7. The gasoline version became available in 2024.