• 4/20/2021
  • 10 min

Cash in on Fuel

  • Jeff Hull
  • 4/20/2021
  • 10 min

Volvo Trucks examines every aspect of fuel efficiency

Ever since the term “miles per gallon” burst into the public consciousness during the OPEC oil embargo of the 1970s, America has engaged in a fascinating and imaginative race to chase percentage increases, running them down until there are fewer and fewer slivers of percentages left to capture—and yet there always seem to be more! Another 0.3% gained from a drive train advance, 0.4% in combustion efficiency, 0.8% from improved aerodynamics, until pretty soon the engineers and designers have squeezed out more whole numbers and re-set the race for more energy efficiency.

MPG—making that number grow, increasing fuel efficiency—involves so many factors. It’s as enormous as the shape a truck punches out of the wind, and as miniscule as shaving a millimeter from the wave form of a piston. It’s as mathematically precise as gear ratios and still as hard to see as streams of data flowing through the air. It’s the hulking totality of the trucks people drive and the subtle differentiations in the way people drive them.

People think of fuel efficiency as a single numeric value—MPG—but so much goes into that one number. At Volvo Trucks, fuel efficiency is an entire philosophy developed around how customers operate their vehicles. 

Start at the core

To understand this philosophy, start at the engine. A truck’s engine is, of course, where fuel is consumed and energy is unleashed. Volvo Trucks has made the D13 Turbo Compound engine (D13TC) standard on the most popular VNL models, because it is the most fuel efficient engine they’ve ever offered and it’s the perfect example of their philosophy in action.

When Volvo Trucks redesigned the D13TC they looked at everything—and optimized most of it. They changed the shape of the pistons so fuel sprayed into the chamber more evenly and is completely atomized, creating a more efficient burn.

Common rail fuel injection allowed more precise control of the timing, also creating more efficiency. Controlling all of these elements electronically instead of mechanically saved energy. Everywhere they looked, Volvo engineers found something to tweak, something they could do a little bit better. And that’s the point—they looked everywhere.

They even looked back in time. The turbo compound concept has been around for 100 years. It’s tried and true technology, an important consideration when you’re chasing efficiency, according to John Bartel, Volvo Trucks director, product strategy-driveline. “We’re always trying to keep a balance between additional cost and customer benefit,” Bartel says. “And you have to look at the added technology in terms of maintenance and the chance of that technology failing. That’s what led us to the turbo compound.”

We’re always trying to keep a balance between additional cost and customer benefit.

John Bartel, Volvo Trucks director, product strategy-driveline

The D13TC engine takes previously wasted energy from the exhaust and transfers that to mechanical energy on the crankshaft. Instead of increasing horsepower, Volvo is using the additional energy to increase efficiency. The engine still provides 455 horsepower, but the amount of fuel it takes to reach that force is reduced. (See our in-depth profile of the D13TC on page 20 of this issue.)

Follow the power

From the engine, the energy released in fuel combustion is transferred to the powertrain. Conserving efficiency here is tricky with so many transfer points, each presenting opportunities for energy to spill away.

Volvo understands that customers tend to think about energy in two ways: as power and as cost. Sometimes the job a truck does requires more power, often at the cost of efficiency. So Volvo looked to offer the best of both. They developed drivetrain packages that placed power and efficiency in a relationship that allowed customers to make choices to meet their needs.

Volvo differentiated the way power is delivered. They customized a package that delivers maximum power—called Performance Mode—that delivers the most torque per horsepower rating available. They created Economy Mode, a balance between acceleration and drivability. And then they came out with Extra Efficiency Mode.

"Extra Efficiency Mode is really focused toward those customers who are extremely fuel efficiency-minded,” says Bartel. “Extra Efficiency has more torque limiting in the software parameters. It controls the rate of acceleration so you’ll go slower cresting the hills, instead of catching back up to speed going over the hill just to slow down on the other side with an engine brake. That’s a huge waste of energy.”

The shape of the thing

The object of the drivetrain, of course, is to push a 40-ton collection of metal and payload down the highway. That takes aerodynamics, thinking about the way air flows over a surface at speed, and finding ways to reduce drag. Today, software programs can simulate not only the aerodynamics of the truck’s exterior, but airflow through the grill, airflow through the radiator, how temperature affects airflow, how crosswinds shove the cab and trailer, and how much yaw a crosswind forces. 

Engineers can simulate real world performance before they take a fully-built model into aerodynamic testing. They can see down to the millimeter when the exit angle off the edge of the wheel well keeps air flowing with the truck, not tripping off into turbulence that costs efficiency. They can see that all the leading edges in the opening of the grill at the bottom of the bumper direct air into the cooling package, rather than letting it dance around inside the hood cavity and create drag. 

But shaping isn’t the only way to affect the fuel efficiency of a massive form. Why, for instance, create friction—often the enemy of fuel efficiency—when you don’t need it? A truck running empty or light doesn’t need all its axles, does it? So Volvo embraced the concept of Adaptive Loading, or lifting an axle off the road when a truck is running light. All that rubber, all that surface area friction, is subtracted from the very complex formula that determines how much fuel a truck burns.

Volvo VNL760 Flowbelow

MPG is a measure of how you do your job  

But fuel efficiency is more than just a mechanical relationship. It’s a mental one. Ask Joel Morrow. Morrow, senior driver and vice president for fleet equipment procurement at Ploger Transportation, says, “In a very real sense, fuel efficiency describes how well you’ve done your job. The components of the truck and engineering, that’s secondary. You have to have the mindset that fuel efficiency is what we’re going to do. Achieving that, establishing that fuel efficiency is important and that we’re going to get it done, that has to be in the company culture.”

Fuel efficiency is the matrix through which everything else can be seen, Morrow says. All of the things a driver does to operate safely, for instance, are also things that increase fuel efficiency. Typically the same sorts of behaviors increase productivity too.  

Saving fuel comes naturally to Morrow.He’s been taught its importance from an early age.

In a very real sense, fuel efficiency describes how well you’ve done your job. The components of the truck and engineering, that’s secondary. You have to have the mindset that fuel efficiency is what we’re going to do.

Joel Morrow, senior driver and vice president for fleet equipment procurement at Ploger Transportation

“My dad wouldn’t run a lawn mower two seconds longer than he needed to, just to save gas. It was an easy thing to focus on because we had that preached to us when we were younger,” Morrow says.

He’s been looking for efficiency ever since, and, like Volvo, he’s been looking everywhere. Morrow was experimenting with downspeeding before OEMs introduced the concept. “We started swapping out ratios and playing with different transmission and engine combinations in the late 1990s. We called it gear fast, run slow.”

The new D13TC version allows Morrow to do more than ever. “I look at traditional ratios, you might run a 3.08 or a 3.25 ratio, then we have downspeeding that starts at 2.79 and goes down to 2.47,” Morrow says. “What we’re doing now is pushing those limits, getting down to as fast as 2.05 with an overdrive, which allows us to have multiple gears at highway speed so we can adjust to operating based on what’s in front of us.” 

Morrow, who works closely with Volvo engineers, is turning his attention to shift logic as the driver looks down the road and tries to understand how the truck should operate pulling different weights, how it should work over different terrain. He’s trying to optimize performance and operate the truck in its sweet spot, regardless of circumstance. Morrow thinks that the more we can program a truck to anticipate changing conditions, the less the driver has to think about.

Volvo VNR
The Volvo VNR 660 sleeper has two fuel efficiency package options and is available with the FlowBelow Aerokit.™

“Drivers get paid by the mile. Their focus should be safely making miles. My job is to figure out how to make the truck smart enough to make the decisions on the road, so the drivers don’t have to,” Morrow says.

Automation fuels gains

What Morrow is referring to, driver behavior, is another place Volvo has looked to wring more miles from a gallon of fuel. Small things, like how long a foot stays on the accelerator when engine braking begins, may seem insignificant—but when repeated hundreds of times a route and multiplied by every driver in a fleet, they add up. 

The Volvo I-Shift automated manual transmission overrides some of those tendencies. For example, it cuts off fuel when the clutch or the engine brake engages. But there are other more subtle developments too. Volvo has designed a software option that slows acceleration for tankers hauling farm product. Typically a milk tanker doesn’t have baffles, which means a lot of sloshing around as the truck accelerates through gears (also the engine brake is dampened a bit during deceleration). The ride progresses more smoothly and energy is saved. 

“Starting in about the 1990s, electronics and computerizing of the engine or other drive components really allowed us to control things to such a higher resolution,” according to Johan Agebrand, Volvo Trucks director of product marketing and strategic pricing, who has been with the company over 30 years. “Suddenly we could just do so much more. We could do certain combinations you couldn’t accomplish mechanically, and we’d get more fuel efficiency out of it.”             

Agebrand says that, initially, electronic controls allowed manufacturers to reap big gains with every tweak. “Twenty years back if we made a software function, that function got us 1% increase in efficiency everywhere,” Agebrand says. “Now you have to improve 30 functions to get 1%. Tomorrow you might have to improve 1,000 functions to get 1%. But we’re going to find them. These improvements reduce costs, reduce consumption, reduce emissions. It’s making transportation more sustainable.”

Where he looks to improve mileage most is situational.

“We’re looking at more unique cases where the truck is doing something specific in special weather or environmental conditions,” Agebrand says. He believes that customizing parameters to meet changing road situations will continue to provide efficiency gains for some time.

Twenty years back if we made a software function, that function got us 1% increase in efficiency everywhere. Now you have to improve 30 functions to get 1%. Tomorrow you might have to improve 1,000 functions to get 1%. But we’re going to find them.

Johan Agebrand, Volvo Trucks director of product marketing and strategic pricing

Data is the new fuel efficiency

All of those gains are enabled by data. The trucking industry has been collecting data about its products for years. Mined correctly, those sets could allow more opportunities to save fuel. Agebrand sees opportunity in data-enabled platforms like predictive cruise control. If a truck can “know” the road ahead, it can shift and brake more efficiently over the course of its route.

Connectivity gives data relevance and value. Data points flow from connected Volvo vehicles all over the country, driving in unique conditions and circumstances. Aggregated, that massive data set can reveal insights about fuel consumption and where gains may still be made.

Connectivity is about getting actual data back from our products and improvements and seeing where they’re optimizing fuel efficiency.

Natalie Martin, Volvo Trucks connected vehicle business development manager

By parsing back through at a more granular level, Volvo analysts can see where vehicles have overperformed and look more closely to understand what’s going so right. They might seek information from the fleet owner or the driver, to better understand conditions and applications. Once that information is known, Volvo can adapt products or adjust parameters to benefit other fleets operating in similar conditions.

“Connectivity is about getting actual data back from our products and improvements and seeing where they’re optimizing fuel efficiency,” says Natalie Martin, Volvo Trucks connected vehicle business development manager. “At the population level, you can make assumptions and apply them to fleet, while at the fleet level you can see where you found gains and apply that back to the population.”

Some people might not see an obvious connection between connectivity and miles per gallon. Those billions of invisible data bytes streaming over our heads—they’re a long way from axle ratios and gear shifts, longer still from pistons and fuel injectors. But all those things, and many more, are offshoots of one bigger thing. 

At Volvo Trucks, it’s more than a single number. It represents a philosophy and a never-ending pursuit of greater fuel efficiency.

Savings by the numbers

For over the road applications, fuel is typically the second largest operating cost. Even small improvements on fuel efficiency can make a big difference in fuel costs.

Average starting fuel economy: 
7.18 mpg

Average cost for fuel:
$3.00 per gallon

Average annual run:
120,000 miles

Average annual fuel expenditure:
$50,139

1% fuel efficiency improvement = $501 per vehicle annually

Driving Progress

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