
The ISB6.7 G engine, based on Cummins’ ISB6.7 diesel, will use Cummins Westport’s spark-ignited, stoichiometric-cooled exhaust gas recirculation (SEGR) technology. Thomas Built Buses launched its Type D CNG-fuelled rear-engine Saf-T-Liner HDX school bus in 1992, since when the company has put more than 1,300 HDX CNG buses on the road and says it has seen demand increase in the last five years.