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Spec for Success: Selling the Benefits of Downspeeding

Customers who constantly hear about fuel economy improvements expect their new engines to deliver more miles per gallon. And with all of the other aerodynamic gains and improvement in tires and transmissions, it’s likely that they will see a drop in fuel usage. But the key to helping them get the most out of every drop of fuel is to spec for success. And that involves being able to explain how today’s diesel engines are designed to deliver the same (or better) performance in a lower rpm range than they did five or 10 years ago.

A small-fleet owner who is used to spec’ing engines at 1400-1500 rpm needs to know that today’s trucks with the SmartAdvantage™ Powertrain should be geared to run at 1150-1240 rpm. An ISX15 with Eaton® UltraShift® PLUS can be spec’d to run at 1250 rpm and still deliver more than sufficient power to handle interstate road grades and loads.

downspeeding chart 2015

The three comparable trucks were run over three routes and duty cycles designed to simulate different operating conditions, and measured by trip times and fuel efficiencies. As expected, all three ratings and powertrain configurations provided exceptional performance in terms of gradeability and startability. The main difference in the specs was seen in the fuel economy. The conventional powertrain spec of a 450hp/1650 rating operating at 1450 rpm was the baseline spec, and provided good fuel economy across the three duty cycles. However, the direct drive that was spec’d to cruise at 1302 rpm and the ISX15 400 SmartAdvantage rating performed far more efficiently. The mpg from composite routes resulted in (across the different duty cycles) a 1.8 percent greater mpg downsped direct-drive spec, and a whopping 5.7 percent less fuel used for the vehicle spec’d with the downsped SmartAdvantage Powertrain. With minimal difference in total trip time or performance characteristics (gradeability and startability) in regional-haul, the 400-hp direct drive delivered mpg comparable to that of SmartAdvantage.

Once your customers understand how engine and trucking technology is changing for the better, you will have an easier time ensuring that they adapt to meet their operational objectives. No one can help them spec for success like Cummins and you.

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