There’s a new crop of engines on the street now that’s cleaner, more fuel efficient and hopefully more reliable than previous models. Most North American heavy-duty diesel engine manufacturers rolled out substantially revamped engines last year to meet the U.S. Environmental Protection Agency’s GHG17 emissions regulations. Those rules were the final step for diesel engines in Phase 1 of the EPA’s grand CO2 reduction plan. Engine makers now have a few years to figure how to meet the next, more restrictive round of fuel efficiency improvements, which come into force for model-year 2021 engines.
According to DieselNet, an independent online information service covering technical and business information on diesel engines, model-year 2017 heavy-duty diesels have CO2 emissions limits of 460 grams/bhp-hr, which translates into a fuel consumption limit of 4.52 gallons/100 bhp-hr. While that won’t mean much to most of us, it forces truck makers to up their game by 7% to 20% compared to MY 2010 trucks — with engines contributing a sizable chunk of those reductions. And, by popular demand, engine makers had to step up the reliability quotient, too.
To meet those goals, engine makers deployed combinations of more advanced electronic controls and mechanical changes to their engine, which in several instances included new injection systems, new piston designs, variable speed accessory drives, low-friction components, lighter lubes, higher compression ratios and new aftertreatment systems. Benefits to the truck owner include in some instances lighter engines, more torque at lower rpm, less horsepower at higher rpm, better drivability and of course reduced fuel consumption.
It’s still a bit early to make a pronouncement on the reliability question, but each of the engine makers’ reps we spoke with emphasized the improved reliability of this engine generation. We’ll know for sure soon enough.
Here’s what your engine makers bring to the table to meet fuel efficiency goals.
Last fall, Cummins rolled out two GHG17-compliant versions of its X15 engine — one to satisfy those most interested in fuel economy, the other for the performance-minded. Both are essentially the same engine, but the Performance version features a few different bits of hardware to give it beefier ratings, while the Efficiency version takes advantage of all the latest hardware and software upgrades targeted at fuel economy.
Jim Nebergall, Cummins’ X15 program leader, says uptime is the focal point of the current program.
“Uptime was our largest priority heading into 2017,” he says. “Our customers told us, ‘it doesn’t matter what else you do, if the
engine doesn’t meet our needs, it won’t be in our fleet.’ So we made a lot of changes to the basic engine such as using more robust materials in engine construction. We changed the wiring harness to reduce the possibility of water ingress. And we looked hard at some of the late-life, off-warranty failures, usually seen by the second owner after 750,000 miles, and said we have to do something about these to bring some value back for the secondary market.”
Cummins has modified a long list of components, such as using a more robust variable geometry turbocharger actuator and a revamped exhaust gas recirculation cooler.
The new aftertreatment system is probably the biggest story. With the previous system, OEMs could package them differently, and that led to variations in performance that had to be managed with sensors and software changes. Now it’s essentially a straight pipe and is the same on every truck.
Gone from the X15 is the so-called 7th injector, the external hydrocarbon injector used to regenerate the diesel particulate filter. Nebergall says Cummins now uses a post-combustion injection of fuel that flows out of the cylinder and into the aftertreatment device to heat the substrate to desired temperatures.
Nebergall says customers won’t see much physical difference in the 2017 engine, but the changes will reveal themselves in longer maintenance intervals, better performance and drivability, and less unplanned downtime.
Detroit Diesel DD13, DD15, DD16
Daimler Trucks North America’s Detroit Diesel business unit had GHG17-compliant engines in production back in 2016. Those will not undergo any significant changes in the 2017 calendar year. While there are no changes to the published power ratings, engine oil drain maintenance intervals have been extended to 50,000 miles for normal on-highway service.
“We continue to offer our customers great fuel economy and reliability, along with lower overall cost of ownership,” says Greg Gusko, communication manager, component marketing at Detroit Diesel.
Meanwhile, Detroit and Daimler Trucks have upped the capabilities of Integrated Powertrain Management. IPM 4 is more tightly integrated than ever with the DT12 transmission and DD15 and DD13 engines. New fuel-saving potential stems from a more advanced predictive cruise control system and integration with its collision mitigation/adaptive cruise control system, Detroit Assurance.
The Detroit Connect electronic interface now includes an easy-to-use interface called the Detroit Connect portal and the Detroit Connect mobile portal app. Users will have access to full diagnostic information provided by the Detroit Connect Virtual Technician remote diagnostic system. Rather than relying upon the e-mail notifications that Virtual Technician delivered previously, the new portal places all that information at fleets’ fingertips.
The new portal will also serve as a hub for other Detroit Connect features that will be available in 2017, such as Remote Updates. This gives fleets the ability to remotely change select engine parameters, such as maximum road speed, as well as to receive Detroit-initiated engine and powertrain firmware updates without having to stop and physically connect the vehicle at a service center.
International unveiled this new 12.4L engine in February, calling it a clean-sheet design using the MAN D26 engine block. It’s said to be 55 pounds lighter than the International N13 and 600-700 pounds lighter than some 15-liter engines, while claiming a B10 design life of 1.2 million miles. Ratings run from 370 to 475 hp and 1,350 to 1,750 lb-ft.
Navistar’s product development manager, Jim Nachtman, says special emphasis was placed on fuel efficiency and uptime right from the start of the A26 project.
“We saw unprecedented results from our validation and testing,” he says. “As a result, we’re able to offer a two-year, unlimited mile warranty that can be extended out to six years or 600,000 miles for overall engine coverage.”
Nachtman says the A26 is in its own right up to 5% more fuel efficient than the N13, and that’s before you add customer options such as predictive cruise control. The gains come from improvements to the air handling system, including a switch to a single variable geometry turbocharger from Borg Warner, from the previous series turbochargers on the N13. The engine uses a common rail injection system with new injectors, new nozzles, and a new fuel pump that develops more than 36,000 psi.
Engineers also did much to reduce
friction between moving parts, while using a cylinder head and cooling module that allow for less restricted movement of fluids through the engine. This reduces the load on various pumps, and thus wastes less fuel. A six-blade fan requires 30 less horsepower to run at 1,400 rpm, Nachtman says. “With less horsepower consumed by the fan and the water pump, there’s more power available at the wheels, which can reduce the number of downshifts required in hilly terrain, which all means less fuel burned to get the job done.”
When coupled with the GPS-based predictive cruise control system, the engine can decide how to most efficiently operate in various conditions depending on expected power demand over the next few miles.
“During evaluation on our ‘Illinois/Kentucky hilly route,’ which is a 98% match with our typical on-highway customer route profile, we exceeded 8 mpg without the benefit of predictive cruise control,” says Nachtman.
The A26 is the new kid on the block this year, so everyone will be watching it closely.
Paccar MX-11 and MX-13
Paccar’s 2017 lineup includes new ratings for the 10.8-liter MX-11 of 430 hp and 1,650 lb-ft, and 510 hp and 1,850 lb-ft for the 12.9-liter MX-13. The MX-11 also gets a new rating on the low end: 335 hp and 1,150 lb-ft. The majority of the MX engine lineup now delivers peak torque at 900 rpm, which supports the wider use of downsped drivelines.
Paccar says it has evolved the injectors and pistons on the MX-13 to drive further efficiencies in the combustion cycle. Engineers have also opted for different turbochargers for engines rated above or below 485 hp.
The GHG17-compliant 2017 MX-13 and MX-11 engines now feature a single cylinder air compressor, along with an electronically controlled variable displacement oil pump (based on pressure and temperature), and a variable speed coolant pump that responds to heat rejection demands. Together, these eliminate some of the parasitic drag on the engine, leaving more output to drive the truck.
“Earlier this year, Kenworth announced an update to its predictive cruise control functionality with the new MX-11 and -13 engines. This update came with the launch of the new 2017-emission engines and provides up to a 1% improvement in fuel economy,” says Kurt Swihart, Kenworth marketing director.
Predictive cruise control combines GPS with cruise control to optimize cruising speed based on topographical GPS data inputs. In certain types of terrain, such as rolling hills, as the truck ascends and crests a hill, predictive cruise control will allow the vehicle speed to drop slightly below the set cruise speed. This boosts fuel economy since the truck is now using momentum instead of fuel to maintain set cruise speed.
Paccar has also developed a single-canister aftertreatment system that combines the DPF, SCR and DEF mixing pipe.
“This innovative single-canister aftertreatment system improves serviceability, extends service intervals and reduces weight by up to 100 pounds,” says Darrin Siver, Peterbilt general manager and Paccar vice president.
Both Mack and Volvo continue to offer three heavy-duty engine platforms for 2017, the 10.8-liter D11 (Mack MP7), the 12.8-liter D13 (MP8) and 16.1-liter D16 (MP10). All are GHG17-compliant, and they feature a number of noteworthy hardware changes.
It all begins with the addition of common rail fuel injection. This is something new to Mack and Volvo, but common on other engines. John Moore, Volvo Trucks’ powertrain product marketing manager, says the common rail system allows for multiple injection events at very high injection pressures.
“This allows for very precise injection timing, and because we can introduce the fuel to the cylinder in stages, we get a more complete burn with less soot production,” he says. “Combined with the wave piston design, which came from our SuperTruck research, we have almost eliminated [90% reduction, Volvo says] soot from the combustion process. That takes a big load off the aftertreatment system.”
Mack’s technology product manager, Scott Barraclough, says the engines also feature a two-speed clutched coolant pump on certain engine ratings for lower parasitic loss. Earlier this year Mack and Volvo added optional turbo-compounding to their 13L offerings, delivering an additional 30-50 hp to the flywheel through fluid-coupled gearing. Looking at it another way, turbo-compounding takes a 50-hp load off the engine for additional fuel savings.
“We have tuned this as an efficiency enhancement rather than a performance addition,” says Barraclough. “If you have a 450-hp engine, you only have to fuel it for say 420 hp, taking that much more load off the engine.”
Mack and Volvo have also improved the design of their aftertreatment system, bringing it into a smaller package and using a copper zeolite catalyst for improved NOX conversion.
Mack and Volvo use the same basic engine platforms but program the engines differently for their own specifications. Both companies say we can expect fuel economy improvements in the 2-3% range in the small block engine, and up to a 6.5% or better improvement in the mid-range D13 and MP8 engines spec’d for downsped operation.