Cummins new ISB6.7 G natural gas engine. Photo from Cummins Engines

Cummins recently confirmed plans to manufacture a 6.7 liter natural gas engine for medium-duty and vocational trucks. With more emphasis on reducing carbon footprint, chances are good that the bus that takes your child to school — and even your next tow vehicle — may be powered by an alternative-fuel engine. We already know that famed engine builder Jack Roush has launched Roush Clean Tech and is offering propane-powered Ford medium-duty trucks. So, it’s no surprise that Cummins will apply cleaner fuel technology to its diesel-engines architectures.

The ISB6.7 G plans, which are based on the inline-6 Cummins 6.7 diesel engine, will include the latest EGR technology developed from a joint venture between Cummins and Westport. Officially called the “spark-ignited, stoichiometric cooled exhaust gas recirculation” or SEGR technology,  the idea is to take a measured quantity of exhaust gas and pass it through a cooler before mixing it with the incoming fuel and charged air to the cylinders. The goal is to lower combustion temperatures, increase power density and reduce engine-knock tendencies. 

Cummins says the ISB6.7 G will produce 30 percent more torque at idle, and economy is improved by percent over the previous Cummins Westport lean-burn natural gas engines. The engine will also incorporate full drive-by-wire with a newly designed electronic control module and a waste-gated turbocharger with a water-cooled bearing housing.

Another area where Cummins is claiming benefits is the maintenance-free aftertreatment. Many diesel engines require active aftertreatment in the exhaust, like diesel particulate filters or selective catalytic reduction systems. Cummins says the ISB6.7 G advanced combustion technology “creates an oxygen-free exhaust” which allows for a maintenance-free three-way catalyst that is packaged as part of the muffler. Expect to hear more on this alternative fuel engine as the manufacturer gets closer to the expected 2015 release date.