TM4, Cummins Jointly Developing Range-Extended Electric Class 7/8 Bus Powertrain


TM4 and Cummins are working together to develop a plug-in hybrid powertrain for class 7/8 transit buses. The goal is to reduce fuel consumption by at least 50 percent compared to conventional hybrid buses. The more flexible, efficient drivetrain allows for longer ranges with zero tailpipe emission capability for in-city routes.

The range-extended electric drive system comprises a gen-set (Cummins’ Euro 2019 B4.5 diesel engine coupled with TM4’s LSG130 electric generator); an external 450 kW ultrafast charging infrastructure; a power collector; a 111 kWh onboard Li-ion battery; a TM4 SUMO electric motor directly connected to the differential; a small fuel tank and power electronics.

The Cummins B4.5 is a four-cylinder diesel engine that is Euro6 emissions compliant. It uses a combination of exhaust gas recirculation and variable geometry turbocharging with a new exhaust aftertreatment using particulate filtration and catalytic reduction. The engine is already very popular as a bus engine across Europe and the United Kingdom.

T4 is an electric powertrain developer whose primary business has been in China. Their generator, the LSG130, has a 135 kW output at 3,400 rpm. Their SUMO drive systems are optimized for medium and heavy duty applications.