Gone are the days where updated HP and torque specs tell the full tale of a new engine launch. Cummins optimizing its 2021 engines on the foundation of its 2017 X15 and X12 platforms shows that there’s still plenty of operational efficiency to be reaped from diesel powerhouses. It’s impressive, but it’s also complicated. It’s the combination of intelligent powertrain control, deeper integration with the Endurant HD transmission and new features like GPS look-ahead and predictive road speed governor that can be hard to understand.

So, I sat down with the Cummins product team to parse through the information and find out what it means to you.

Fuel efficiency gains explained

Here’s the breakout of Cummins’ efficiency gains benchmarks.
❱  X15 Efficiency Series (compared with 2019MY): +3.5%
❱  X15 Efficiency Series with EX rating, which requires the Endurant HD transmission and GPS look-ahead data: Up to an additional 1.5% on top of the gains above.
❱  X15 Performance Series (+500 HP applications, compared with the EPA 2017 engine): +2%
❱  X12: +2.5%
❱  X12 with EX rating available in 2021: up to an additional 1.5%.

The question remains: If these are essentially the same engine hardware platforms, where does the improved efficiency come from?

“The bulk of what has changed is internal components,” said Kris Ptasznik, heavy-duty on-highway product manager, Cummins. “In the X12, for example, we identified components through long-hour and high-abuse testing where material modifications reduce the likelihood of a failure. Major hard parts and soft parts were evaluated. These changes did not add any weight to the product. In terms of total cost of ownership improvements, we’ve improved engine breathing, increased compression ratio and reduced frictional losses through modified ring packs to improve overall efficiency.

“We also offer an optional longer fuel filter that extends maintenance intervals to match market-leading oil-drain intervals already available with the 2020 X12.” (More on oil drain intervals in a minute.)

Cummins noted that the 2020 X15 Efficiency Series already met 2021 EPA guidelines, hence the efficiency comparison to 2019 MY. The engine OEM also explained why it’s so difficult to nail down an overall MPG number fleets can expect.

“We have select customers routinely seeing 9 MPG with both X12 and X15 engines, but the diverse use of our products makes delivering a specific fuel economy number difficult,” said Nick Roth, director of national accounts, North America sales, Cummins. “What we can say for sure is we released a 2021-compliant product in 2020 with the X15 Efficiency Series.”

On the X15 Performance Series, Ptasznik noted that Cummins improved the air handling system for better compression ignition and engine efficiency.
“At the same time,” he continued, “we focused on reducing parasitic and frictional losses by improving the power cylinder, reducing the water pump speed and resizing some critical components.”

What are EX ratings and how do they provide a fuel-savings boost?

This is where the bulk of the intelligent powertrain control comes into play. It includes on-ramp boost, predictive engine braking, predictive gear shifting and dynamic power, which is exclusive to Cummins EX ratings when integrated with the Endurant HD transmission, GPS and compatible connectivity modules.

Here’s an overview of each:

• On-ramp boost uses GPS to sense when the truck is merging onto the highway then trades fuel economy for maximum torque and a performance-oriented shift schedule to reduce the time required to get up to merging speeds and then returns the vehicle to its normal settings.
• Predictive engine braking looks at the grade ahead via GPS to engage engine brakes early to maintain a maximum speed.
• Predictive gear shifting also leverages GPS data to set the most efficient shifting schedule for the road ahead.
• Dynamic power adjusts torque to allow lighter loaded trucks to perform like heavier loaded trucks on grades to provide fuel savings on lighter-loaded trucks by delivering consistent performance.

Like AMTs before them, these features aim to take the variability out of the operation. The keyword is “consistent”–you want to keep the engine in its efficient operational sweet spot for as long as possible. And this is just the beginning of technology-enabled efficiency features.

“Some OEMs are selling nearly 50% of X12 and X15 Efficiency Series hardware with these features from the factory,” Ptasznik said. “As far as new features that are coming, there are some additional features geared towards fuel economy that will be released over the next several years.”
On top of all of this, Cummins unveiled a new connectivity module called Acumen that offers another path to the Cummins suite of connectivity features and can provide the look-ahead data to enable EX ratings features.

What about the longer oil drain intervals?

The driving trend in engine oil drain intervals has been to push them further. Of course, your fleet’s ability to do that greatly depends on your engines’ MPG. The current Cummins oil drain interval for the X12 and X15 is set at 75,000 miles for fleets with 7+ MPG, and fleets have the opportunity to extend that up to 100,000 miles by participating in the Cummins OilGuard program. Cummins noted that for 2021 MY, fleets running the X15 between 5 and 7 MPG will see their oil drain intervals extended by 10,000 miles compared with the 2017 X15; an extension that the X12 already has today. Cummins has also matched the fuel filter and oil filter changes on both the X12 and X15 engines to avoid separate maintenance services.

The process for oil drain approval is closely monitored by Cummins pros. It’s backed by the aforementioned Cummins OilGuard program that is free to customers who sign up. Cummins uses the combination of engine performance data and engine oil analysis to safely optimize oil drain intervals up to 100,000 miles.

The first step is providing Cummins with operational data that shows truck duty cycle consistency to provide a ballpark MPG for your overall fleet.
“We don’t want linehaul running out of Cleveland, Ohio, and regional haul running out of Phoenix, Arizona,” Ptasznik explained. “If you’re truly a coast-to-coast operation, then that’s low enough variability to say that you’re the same. Or if you have a regional line that’s hub-and-spoke operations, then your duty cycle for those trucks is the same. Once we understand the duty cycle makeup of the fleet we test somewhere in the neighborhood of 10 to 20 trucks, unless you’re a smaller fleet and then we may test five.”

Cummins sends out pre-labeled sample kits that the fleet returns every 7,500 miles to track oil degradation trends.

“We allow you to extend the maintenance on trucks being tested from day one,” Ptasznik said. “With us testing the samples in-house at such a close interval, we’re able to turn results around quickly to find the oil degradation limit and tell fleets to change their oil when they hit their limit because we know they won’t make it to the next 7,500-mile interval.

“Customers do that for two oil drains at the extended interval, they collect ECM images and send them to us. From there we extend that interval to the rest of the fleet and have them send us a spot check the next time they change the oil just to make sure. So the testing is a little rigorous at first, but then we’re pretty hands off.”