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X15™ Gearing Recommendations: Getting the Best for Your Customers

Customers looking to replace equipment with Cummins X15 may have some questions in terms of where they should operate the vehicle. Now, the X15 Gearing Recommendations have been optimized for clarity across customers and markets. Previously dealers, fleets and owner-operators might have received different gearing recommendations depending on who they were talking to. In order to make sure you help your customers get the best spec for their truck, we’ve streamlined the gearing recommendations for 2017.

The following graphic shows rpms at corresponding target cruise speed ranges for the given operational objectives with each X15 Series engine.

X15 Performance and balance graph: Performance X15 & Efficiency X15 X RPM at Target Cruise Speed

The first and most important consideration when spec’ing a new powertrain is to look at your customer’s current equipment as this will dictate performance expectations. While “Max Fuel Economy” and “Fuel Economy” are specific ranges listed on the graph, and in PowerSpec, fuel economy for a given customer is relative.

Previously ISX, and EPA 2010 vintage ISX15 engines would be geared to operate between 1370 and 1450 for fuel economy. With the availability of peak-torque at 1000 rpm in 2013, the standard rpm range for fuel economy changed and ‘downspeeding’ became an industry trend. In 2017, downspeeding is getting a boost with the availability of 1850 lb-ft of torque at 1000 rpm with the X15 Efficiency Series. And with the recent announcement of the SmartAdvantage Powertrain capable of 1550/1850 lb-ft torque and compatible with 2.47 rear axle ratings, customers looking for maximum fuel economy can spec the engine to cruise at 1075 rpm.

This combination is not for everyone. Customers looking for better performance while maintaining strong fuel economy returns can spec a SmartAdvantage Powertrain up to 1250 rpm. For customers looking for fuel economy outside of the SmartAdvantage Powertrain, automated manual transmissions (AMTs) and manual transmissions between 1250-1350 rpm can be spec’ed. For customers looking to spec a powertrain to cruise close to 1250 rpm, it is recommended that an AMT should be strongly considered for enhanced driver comfort.

The balance rpm range for the X15 Efficiency Series is 1350-1550 rpm at cruise speed. This range is intended for customers that would like a blend of fuel economy and performance. For the X15 Efficiency Series the 1350-1550 rpm range is the range best suited for vocational applications, as spec’ing below 1350 can lead to a lack of power and/or productivity.

For customers spec’ing the X15 Performance Series, the balanced rpm at cruise range is also 1350-1550 rpm. Peak torque is available throughout the majority of this rpm range, while peak power is available towards the upper limit of the balanced spec’ing range. Similar to the X15 Efficiency Series, the balanced rpm range with the X15 Performance Series provides a blend of fuel economy and performance, with more of a focus on fuel economy toward 1350 rpm and more focus on performance toward 1550 rpm.

For performance-oriented customers, the X15 Performance Series spec’d in the 1550-1750 rpm range will ensure that they have access to peak power while cruising or operating at target speeds. The performance operational objective is perfect for customers that favor productivity over operating costs.

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