With the introduction date of Euro 6 equivalent regulations still undecided, Cummins is not waiting for Euro6 to come along. It has declared its intentions to provide the fuel economy benefits of Euro 6 to its customers while Euro 5 is still in force.
“We began to do our test cell and field test work, optimising the duty cycles and hardware, things like turbo matching, to get the best fuel economy results,” says Mike. “As this unfolded it occurred to us that we had significant entitlement to take the next step in vehicle efficiency management with our current Euro 5 product.
“Given the fact that ADR 80/04 legislation was still gyrating around in the halls of Canberra, we didn’t want to wait until it was mandated to give our customers the fuel economy benefit. So we started doing some work around the possibilities of down-speeding our current (Euro 5) X15 product and in so doing we realised the potential for significant fuel savings.”
This is the part where it gets rather interesting because in the push for optimum fuel efficiency Cummins has collaborated like never before with its ‘powertrain partners’, specifically transmission manufacturer Eaton but also drive axle producers Dana and Meritor.
“We’ve always worked hard at optimising our engines to the duty cycle of the line-haul B-double prime mover while our colleagues at Eaton have done likewise with the shift points of their AMTs, but in the past we basically worked independently of each other,” says Mike. “We’ve found that when we do these things together we end up with a truly integrated powertrain, known logically enough as Cummins Integrated Powertrain, that optimises fuel economy.”
Field testing of a super tall final drive ratio of 3.21:1 with Euro 6 compatible engines has been going on but the ratio chosen for optimised versions of the current X15 will not be near so tall.
“We can’t go as tall as what we’re talking about with Euro 6, largely because we’re running a different turbo and the hardware set is not matched to do that,” says Mike. “But what we did find is that we could run a significantly taller ratio than we had previously ever thought possible.
“So the calibration we’ve come up with for Cummins Integrated Powertrain is 550 hp (410 kW) and 2050 ft lb (2779 Nm) of peak torque at 1000 rpm matched to the line-haul B-double duty cycle running a 3.73:1 final drive ratio. With standard tyres this gives a 100 km/h cruise at 1400 rpm which in Cummins land is a pretty tall diff ratio.”
As the conversation continues, Mike reveals some interesting facts in relation to how much fuel can be saved by reducing the cruise rpm.
“For every 100 rpm we drop from the cruise speed we’re seeing a minimum of 1.5 percent improvement in fuel economy,” says Mike. “So by dropping say from a 4.3 to a 3.73 rear axle ratio we’re seeing north of four percent in fuel economy improvement.”