That mirrors the choices for the diesel version of the B6.7, and the two engines' torque curves look very similar, with the diesel hitting its peak at 1400 rpm and the gas engine making its 660 ...

Estimated torque curves show the gasser hitting its stride around 1,600 rpm, depending on the state of tune, compared with a typical Cummins diesel, which is hauling the mail at about 1,200 revs.