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Spec for Success: Keys to Customer Satisfaction

When customers have had good (or even great) success running engines at a particular horsepower or torque rating, convincing them to make a change can be difficult, especially when it involves going down in power or torque and operating at 200 to 300 rpm lower. Partly, you need to assure them that their competitors aren’t settling for the “status quo” and that changes in technology, including fully integrated powertrains and vehicle aerodynamics, have made it possible for fleets and owner-operators to get the same or better performance from an engine with a 400 hp-to-475 hp rating and reduce fuel use in the process.

Cummins has conducted extensive simulation and real-world testing on a variety of ratings and powertrain configurations looking at factors such as startability, gradeability, reliability, durability and number of shifts required over the course of a specific route. The results have shown that an ISX15 in certain applications with a 400 hp-to-475 hp rating can provide performance similar to that of ratings above 475 hp.

Specifically, a simulation was performed on an ISX15 rated at 475 hp with 1650 lb-ft of peak torque, which was compared to an ISX15 485 with a peak torque of 1850 lb-ft using the exact same vehicle profile, aerodynamic package (classic flat-front cab style) and tire sizes. The axle ratios were spec’d for each horsepower – at 3.36 for the 485 hp, and 2.47 for the 475 hp. Cruise speeds for a 200-mile journey were calculated at 70 mph highway (80 percent of the drive time) and running 55 mph on two-lane rural roads, with a gross vehicle weight (GVW) of 80,000 lb. The difference in total trip time was less than eight minutes. The 475 hp/1650 lb-ft ISX15 required only one additional shift (86 vs. 85) compared to the ISX15 with the 485 hp/1850 lb-ft rating, but the reduction in fuel use was approximately 15 percent.

rpm cruise chart

How do you explain to customers that they don’t need 485 horsepower anymore? First, talk to them about the improved efficiencies in vehicle aerodynamics and rolling resistance. Compared to older trucks that required 485 hp (or more) to efficiently overcome road load conditions, a 400 hp-to-475 hp engine can meet the demands of most operating conditions while operating at a lower rpm due to the early availability of peak torque. Second, discuss the myth that operating a higher-horsepower engine (485 hp compared to 450) for the same amount of work does not necessarily improve the reliability or durability of the engine. Instead, one of the most important factors in improving engine reliability and durability is the displacement of the engine. Big-bore engines allow for peak torque and power to be achieved at a lower rpm, which operates the engine in a more efficient manner while improving overall drivability. Third, tell them about the different components used in the 400 hp-to-475-rated ISX15 engines versus the 485 hp-to-600 hp. The turbocharger, piston design and water pump are all bigger and heavier to handle higher power output, which is rarely needed in most hauling applications and routes. One very significant difference in components is the intake throttle valve; 400 hp-to-475 hp ISX15 engines come equipped with it while 485 hp-to-600 hp engines use the turbocharger alone to manage Exhaust Gas Recirculation (EGR) flow. This difference alone is responsible for a 2 percent fuel-economy advantage for 400 hp-to-475 hp ISX15 engines.

As always, you don’t want customers to feel like you’re trying to “sell” them something. Simply tell them that you aren’t making any more money by recommending a 400 hp-to-475 hp rating; you are just providing facts that they should consider – especially if they are looking to reduce fuel costs. Partnering with your customers and providing them with the best advice (even if they aren’t ready to hear it) is a great way to show that you are working in their best interest.

Once a customer is ready to consider a 400 hp-to-475 hp rating, the next step will be to test drive a similarly spec’d truck, which will help to alleviate any concerns and demonstrate the pulling power and fuel efficiency in real-world use.

There’s no doubt that with today’s integrated powertrains and the advanced controls technology now available on Cummins ISX15 engines, your customers can now get the driver-pleasing power and fuel economy gains that will deliver higher satisfaction and customer loyalty for their business.

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