Engine innovation: Cummins ISX15

| September 27, 2012
Equipment Editor Jack Roberts checks the oil in the ISX15 in this Peterbilt 386, which serves as a test vehicle at a Cummins research facility in Indiana.


ISX15 Specs (as tested)
Tractor: 2012 Peterbilt 386
Engine: ISX15 Family 1
Power rating: 450 horsepower at 1,750 rpm
Gearing: 1,235 at 65 mph
Transmission: Eaton-Fuller RTLO-16913A 13-speed manual
Axle: Dana 3.08
GVW: 75,000 pounds

As a young man, Clessie Cummins worked as a chauffeur for a banker and gained a reputation for his mechanical aptitude. By 1919 he had founded a small-engine company in Columbus, Ind.

His early efforts – small diesels for farm applications – fared poorly, and his engine sales to yacht makers dried up with the Depression. But once he struck a deal to convert a supermarket’s fleet of trucks to Cummins diesels, his company’s future was secured. Today, Cummins has more than 6,000 dealers in more than 190 countries.

The company hasn’t lost its founder’s spirit of innovation. For example, it’s taken a leading role in the development of heavy-duty natural gas engines for trucking. But the diesel truck engine is where the company’s roots are, and Cummins’ creative design continues there as well. Now that the drawn-out emissions war of the past few years is settled, Cummins is preparing to launch its next generation of heavy-duty diesel engines. Overdrive was lucky enough to get one of the first test drives of these new engine families.

The test truck Roberts drove during his time with the ISX15 — a Peterbilt 386 Cummins owns and uses.

The new ISX15 will appear in new trucks early next year. The engine is amazingly smooth and surprisingly quiet. Because it’s a smart engine, you might have to break a habit or two in terms of shifting patterns or gear selection in order to get the most out of it. But Cummins has designed it in a way that it coaches drivers to get the best fuel economy possible while delivering plenty of power – all the while making the driver safer and more productive.

Lou Wenzler, on-highway communications director, says that Cummins today is all about boosting fuel economy in its engine designs, with targeted improvements of up to 2 percent over its current engines. Since the engines burn less fuel, the improvements allow the new ISX15 to already meet 2014 Federal Greenhouse Gas Emissions regulations.

“We’re also going to offer better performance from these next-generation engines,” Wenzler notes. “Drivers will notice improved response to their throttle inputs along with taller gearing and ‘smarter’ electronics that will allow them to drive better by helping manage power demands while still delivering improved fuel economy.”

The ISX15 I’m driving on this crisp June day is a prototype engine mounted in a 2012 Peterbilt 386 that Cummins keeps at its product evaluation lab on the outskirts of Columbus, about an hour south of Indy off I-65. The engine churns out an impressive 450 horsepower while running at 1,750 rpm.

Cummins plans three versions of the ISX15, based on torque and horsepower. This test engine, what Cummins calls a Family One, will be introduced for fleets next year. A Family Two version for owner-operator and premium fleet trucks, as well as a 600-hp Family Three variant for heavy haul, will follow soon afterward.

To help boost fuel economy, Wenzler says, engineers worked hard to reduce parasitic loads inside the engine design, including a new, optimized fuel pump with reduced internal friction, a newly designed variable geometry turbocharger and a new intake throttle design to optimize EGR flow in the engine.

“We’re looking at every detail, no matter how small,” Wenzler adds. “For example, how fast do you need to spin a water pump to maintain cooling efficiency? And how does that affect fuel economy? Nothing is off the table.”

  • jescott418

    My problem with engines today is not that they are not smooth in operation or that they are providing enough power. Or even that they don’t get good fuel millage. The problem of course is the added cost of maintaining the added parts for the emissions. The used truck market is already showing that post emission trucks are taboo. Nobody wants the headaches.

  • Straight Into Face

    Thats why they keep coming with “new” engines all the time – to make that false impression the problems are gone

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