Are smaller displacements the engine trend of the future? Cummins seems to think so and is hedging its bets on the question. The Columbus, Ind.-based global engine manufacturer now has very capable engines at both ends of the Class 8 spectrum: the 14.9-liter X15, and a brand new engine platform, the 11.8-liter X12.
Recent introductions from other engine makers suggest there’s an appetite for smaller block engines that can deliver Class 8 power for regional and urban applications as well as the vocational market. With ratings up to 475 horsepower and 1,700 lb-ft of torque, the X12 will be running with the big boys. But the X12 is nearly 1,000 lbs lighter than the X15, so weight-sensitive fleets will be looking very closely at this engine.
The X12 is derived from the ISG platform first introduced in 2013 as a global engine platform. It made its first appearance a year later in a joint venture with the world’s largest independent engine maker, Beiqi Foton Motor Co. Ltd. of China. Foton now uses the ISG diesel in a new truck series developed with Daimler of Germany.
Cummins says the engine in ISG trim already has more than a billion miles under its belt and is ready to take on North America. We will see it here in 2018 as the X12.
This is not a rebranded ISX12. The diesel version of that engine will be sunsetted at the end of 2018, although Cummins will continue to stock parts and cover service for decades, and production of the natural gas version will continue into the foreseeable future.
Instead, the X12 is a clean-slate design from the oil pan up. It was engineered to be a robust, lightweight, high-output engine using composites and advanced structural concepts to provide the needed strength without adding unnecessary weight.
“The X12 was designed from the ground up to reduce weight wherever we could while maintaining superior dependability,” said Jim Fier, Cummins vice president of engineering, speaking at the X12 unveiling in July at the Transportation Research Center in central Ohio. “The block uses minimal material but is reinforced by an innovative network of supports. They have even eliminated unnecessary material from the flywheel housing to reduce weight.”
The X12’s innovative architecture results in a remarkably low dry weight of just 2,050 pounds. Substantial weight savings are also achieved by the use of high-strength composite materials for the oil pan and valve cover.
“It’s more than 150 pounds lighter than its closest competitor, and 600 pounds lighter than the average competitive engine in the 10- to 13-liter space,” Fier said. “The engine offers fleets that much more payload without any trade-off in power or durability.”
Mechanically, the X12 features a single-cam in-head design with a roller valvetrain along with high-efficiency intake and exhaust ports and the latest version of the Cummins variable geometry turbocharger. The Cummins Xtra-High Pressure Injection (XPI) fuel system boasts injection pressures of 29,000 psi at all engine speeds and it’s capable of multiple injection events for quieter, more efficient combustion. The engine brake is integrated into the exhaust rocker levers and is said to produce up to 50% more braking horsepower than typical bleeder-type compression brakes.
The X12 comes off the assembly line ready to incorporate Cummins’ Adept, Smart-Coast and Predictive Cruise Control functions. It will come from the factory wired for Cummins Connected Calibration and Connected Tuning applications, along with Connected Diagnostics to improve serviceability and reduce downtime.
For vocational and emergency truck applications, the X12 offers front and rear power take-off drives and a side-mounted drive. It will use Cummins’ patented Single Module aftertreatment system, and it’s factory-compliant with Phase 1 greenhouse gas and fuel-efficiency standards.
The X12 is quiet. Really quiet. And it doesn’t sound European. When you crank it over and it comes to life, it sounds like any other Cummins – but quieter.
We had the chance for a single lap around the 7-mile oval track at TRC, which isn’t much to formulate an impression. The trailer was empty as well, so I really couldn’t gauge its performance except to say it felt pretty peppy. With the powertrain in the truck, we cruised at 65 mph at 1,125 rpm, and up to 72 mph at 1,250 rpm, which suggests a degree of downspeeding designed into the drivetrain. Most of the upshifts in the lower gears during the launch sequence took place in the 1,400-1,600 rpm range.
The performance of the engine brake is notable, and the programmed downshift points are timed to keep the engine revs in the higher range for optimum retarding power. This may be an optional parameter, but it downshifted all the way into 3rd gear when we had completed our lap.
Cummins had a Daimler Cascadia daycab (113 in. BBC) at the launch with an X12 installed. The engine fit neatly under the hood and it didn’t appear that routine maintenance would be too tight a squeeze. I didn’t tip the hood on the ProStar I drove on the track, but there likely would have been enough room for two X12s under that hood.
I can hardly make a pronouncement based on a single 7-mile lap around a track, but from what I saw, I suspect Cummins will have a full slate of orders for the X12 by the time it hits the streets in 2018. It will be manufactured at Cummins’ Jamestown, N.Y. engine plant.