Powertrain

The Powertrain Is A Prime Opportunity for Increasing Fuel Efficiency

Powertrain includes the cooling system, accessories, engine, transmission, hybrid system, driveline, and aftertreatment. Given that this system provides the power for the vehicle, many choices can be made in this area to improve freight efficiency.

Many choices are hard to recognize, as they may be internal to the engine, transmission, and other components. These choices, such as gearing, engine parameters, and cruise controls, help ensure the vehicle is designed for its specific duty cycle and for performing the work required in the most efficient manner.

Powertrain

We test with a minimum of 30 units in our own fleet. Items need to be driver-proof. Items need to be robust and not break down, especially if it takes a unit out of service.

– Vice President of a Large Fleet

Natural Gas And Greenhouse Gas Reduction

Natural gas (NG) is a fuel that has the potential to help reduce total greenhouse gas (GHG) emissions, but also has significant advantages in reducing the more immediate and local health effects caused by air pollutants like nitrogen oxides (NOx) and particulate matter (PM).

The net CO2 benefit of a natural gas engine is in the range of 13% to 18% compared to diesel fuel. Natural gas produces approximately 27% less CO2 per unit of energy on a fuel-comparison basis compared with No. 2 diesel fuel. However, the natural gas engine is less efficient than a diesel.

While natural gas has been used in combustion engines for decades, currently there is a renewed interest in using it in transportation because it is a lower-carbon fuel than diesel fuel and is cleaner burning. In the past few years, the capacity to produce RNG has grown significantly and RNG now represents 68% of the natural gas used in transportation in California in 2023.

When evaluating the natural gas option, there are many financial considerations. More specifically, fleets should consider and compare natural gas to diesel and other alternatives including battery electric from a variety of standpoints. It can take five to 10 years for fleets to see payback from their investment in natural gas vehicles and infrastructure. During that time there are likely to be significant improvements in battery electric vehicles which will offer many benefits to fleets. Having invested in natural gas, they may not be able to pivot to take advantage of the many benefits of battery electric vehicles.

As with any technology there are both benefits and challenges for fleets when it comes to natural gas as a power source for their trucks. Perhaps the biggest benefit is that natural gas vehicles can be a near-zero solution. Plus, there is already some fueling infrastructure in place. On the challenge side, is the fact that they are lower in efficiency in miles per diesel equivalent and there may not be incentives to purchase them.

RNG is a form of natural gas that can be used as a fuel to power vehicles. It is fully interchangeable with conventional natural gas and has significant environmental benefits. RNG is generated from various feedstock sources such as livestock (e.g., animal manure), landfills, wastewater, and other sources. Negative carbon intensity (CI) can be achieved through animal waste.

Findings

  1. There appears to be a wide range in perception and results regarding the business case for natural gas.
  2. There are several positive environmental aspects of natural gas engines.
  3. There are environmental concerns with natural gas.
  4. Sustainability goals, regulations, and the California conundrum are considerations.
  5. The new 15-liter Cummins X15N engine seems promising.
  6. Aftertreatment is simple and more reliable.
  7. Natural gas is very abundant in the US.
  8. There is a question as to whether there will be an ample supply of RNG.
  9. Because of economics and the environment, there are a few points to consider when comparing BEV and CNG. 

Electronic Engine Parameters

Trucking Efficiency has a high degree of confidence that optimizing engine parameters improves fuel economy and is well worth the effort. Depending on a fleet’s current operations, the payback can be rapid and significant. However, optimal fuel performance does not happen without a concentrated effort.

Fleets that are already managing their electronic engine parameters can see fuel economy gains of around 0.5 mpg from optimizing the parameters, but gains can be even higher if the fleet employs drivers with poor driving habits. Fleets that previously have not used parameters to optimize for fuel economy—often due to confusion surrounding terminology—can see fuel economy improvements in the 5-8% range. No testing was done, although fleets and engine manufacturers provided insights into the fuel economy benefits offered by optimizing parameters.

While engine parameters have been around since the advent of electronically-controlled diesel engines in the mid-1980s, not all fleets are using them to optimize their vehicles for fuel efficiency. Today there are more than 100 different parameters available for fleets to set, many of which can benefit fuel economy. In our study, we organized parameters into six categories: vehicle speed limits, vehicle configuration information, engine speed limits, idle reduction, driver rewards and miscellaneous MPG-related.

Optimizing engine parameters is well worth the effort—it enhances fuel economy and saves fleets a lot of money. But the complexity of optimization is preventing many fleets from enjoying the benefits.

– Dave Schaller, Director of Industry Engagement, North American Council for Freight Efficiency

Benefits

Fuel Economy
Fuel economy improvements in the 5-8% range are possible for fleets when they optimize all parameters for fuel economy. Meanwhile, improvements of 3-5% above the defaults may be available to fleets who simply set the parameters of their new trucks in a few key areas such as vehicle speed and idle reduction.

Weight & Cost
Since they are an integral part of the engine control software, engine parameters add no weight or cost.

Challenges

Large Number of Options
Substantial effort is required to fully understand the many parameters available on today’s engines. In addition, new parameters to further improve fuel economy are being created on a regular basis.

Interrelations Between Parameters
Changing one parameter often means having to change other parameters. All parameters must be tailored based on the overall truck specification.

Diversity of Terminology
Each engine manufacturer uses its own terminology and/or brand names for its parameters. Parameters may even be called different things from one engine model to the next.

Variation in Ordering Tools Required
Procedures and tools for setting parameters vary widely by manufacturer and in some cases require intervention by the manufacturer. No single tool can be used to set parameters on all brands of engines.

Incorrect Initial Parameter Settings
There have been persistent issues with parameters being set incorrectly or incompletely at the factory, modification center or dealership, even after the fleet has chosen and communicated its parameter settings.

Variation in Service Tools and Lack of Telematics
When a fleet wants to change parameters, someone has to physically connect to the truck to make the changes. Current telematics technology does not allow changes to be made remotely.

Driver Acceptance
It can be difficult to get buy-in from drivers who may feel the fleet is trying to restrict the way they drive.

Parameter Records Maintenance
Maintaining records for different models of engines and vehicle specifications can require a lot of work. It may be difficult to keep track of all the changes to parameters especially in a mixed fleet.

Common Fleet Strategies

Fleets of all sizes commonly use the accelerators vehicle speed, cruise control speed and idle shutdown parameters. Other parameters may be set depending on the goals of the fleets and their understanding of what those parameters can do for them.

The following are some of the best practices fleets are using with their electronic engine parameters:

  • Keeping a record of parameter settings
  • Developing a template that covers a group of similarly spec’d trucks
  • Performing pilot reviews with manufacturer parameter experts
  • Verifying that vehicles are set up correctly
  • Having the proper tools and training fleet and dealer employees to change parameters
  • Using passwords to protect parameter settings

What People Are Saying

Executives from nine large fleets were interviewed to find out about their experience with engine parameters.

  • Parameter settings varied considerably within each fleet given different drivetrain gear ratios, transmission types, idle-reduction systems and other operational features.
  • The fleets indicated there is confusion surrounding parameter terminology and feature availability between engine manufacturers because there is no standard language to describe parameters.
  • Seven of the fleets found that making desired changes to their settings was either difficult or extremely difficult.
  • When asked about the challenges related to mergers and acquisitions, there was general agreement that it was extremely difficult to get the newly-acquired vehicles programmed to match the rest of the fleet.
  • All nine fleets were positive in their desire to have a telematics system that could report on parameter settings and ideally be able to reprogram parameters remotely.

– NACFE Fleets

In conjunction with Michelin, the study team received feedback from 45 members of Michelin’s Fleet Forum about their opinions of engine parameters.

  • More than half the fleets responding to the survey said they have never been given assistance in optimizing engine parameters.
  • The majority of fleets said their parameters are set identically across their entire fleet.
  • A vast majority of these fleets indicated that they never make changes to the parameters once they are initially set.

– Michelin Fleet Forum

  • Sales personnel said they felt that fleets understood some of the more common parameters like accelerators, vehicle speed, cruise control speed and idle shutdown parameters, but were less well informed about others, especially those dealing with progressive shifting, engine speed and other settings.
  • When completing new vehicle orders, half the salespeople said they contact the customer to make sure they have the most recent parameter settings.
  • Others said they simply use the parameter settings from the last truck order.
  • Salespeople who worked with fleets to optimize engine parameters for fuel economy saw fuel economy gains from 0.2 mpg to as much as 2.5 mpg.
  • The higher mpg improvement resulted from a driver not being in the highest gear at highway speeds.

– Dealership Sales Staff

Decision-Making Tools

The study team developed several tools to help fleets in making their decision about electronic engine parameters. The Confidence Matrix informs fleets of the study team’s confidence in the technology being studied versus the payback a fleet should expect to receive from the technology. The Manufacturer Parameter Name Comparison Chart shows the various names engine manufacturers use to describe key engine parameters. The Engine Manufacturer Information Tool provides manufacturer contact information for fleets needing assistance with optimizing parameters.

Conclusions

  • Engine parameters are proven in their ability to enhance fuel economy, but it appears only large fleets have worked to optimize the settings.
  • Variation in terminology among engine manufacturers as well as variations in drivetrain specifications can make optimizing the fuel economy parameters challenging to any fleet running several brands of engines.
  • It is essential for fleets to have processes around the management of their engine parameters to ensure they are delivered and operating as expected.

Automated Manual Transmissions

NACFE is highly confident that automated manual transmissions offer a good business case for adoption today.

Fleets should expect to see an average 1–3% improvement in fuel economy from automatic manual transmissions, which use a computer to shift the manual transmission at the optimal time. They are much easier to drive than manual transmissions because they eliminate the manual shifter and clutch.  These enhancements result in lower driver turnover, which in turn reduces recruiting and training costs.

Improved driver recruitment and retention are big factors behind many fleet owners’ decision to specify these transmissions over manual transmissions. In addition, they reduce the variability in fuel economy from one driver to the next.

Note: All benefits and consequences are the same for automated manual transmissions (AMTs) and automatic transmissions except for the fuel economy performance.  AMTs offer 1-3% fuel economy improvements and enable even higher levels of performance in future with features such as downspeeding, and the use of GPS to better manage hills and valleys.   Fuel savings from automatic transmissions are yet to be determined.

Benefits

Fuel Savings
Because electronics are making the decision about when to shift gears, the truck shifts into the right gear when it needs to without driver intervention. Fuel economy benefits range from 1% to 3%, depending on other vehicle specifications and operating conditions.

Driver Recruitment & Retention
Many driver recruits have no experience operating vehicles with manual transmissions. Specifying trucks with automated manual transmissions enlarges the driver pool, which is a key advantage given the current driver shortage. Since these transmissions make the trucks easier to drive, drivers will be less tired at the end of the day, which should help fleets with driver retention.

Lower Driver Training Costs
Driver training time will be shortened because operating an automated manual transmission is less complex than operating a manual transmission.

Less Variability in Fuel Economy
AMTs decrease the variability in the fuel economy of trucks or drivers in a fleet, compared to the variability in fleets using manual transmission. Electronically controlled transmissions make poor drivers much better, average drivers better and good drivers slightly better.

Driver Performance & Safety
Electronically controlled transmissions improve driver safety because they allow the driver to concentrate on the road ahead rather than having to worry about shifting. The driver can keep both hands on the wheel.

Technology Enabler
Electronically controlled engines, transmissions, and other powertrain components offer the opportunity for improved and fine-tuned performance for various duty cycles and terrains.

Challenges

Higher Initial Costs
Vehicles specified with automated manual transmissions can cost as much as $3,000 to $5,000 more than similar vehicles with manual transmissions.

Resale Value
While there is not a great deal of data on resale value as many of the trucks with automated manual transmissions have not made it to the secondary market, fleets are confident that trucks equipped with automated manuals will not take a hit at resale time. Currently, automated manuals can bring $1,000-$3,000 less on the resale market, however most fleets have not yet traded their trucks equipped with automated manuals. Expectations are that residual values will be on a par with trucks equipped with manual transmissions.

Maintenance
Electronically controlled transmissions have more moving parts and require software to operate. As a result, fleets expect a small increase in maintenance cost.

Specification Issues
To get the most from electronically controlled transmissions, care needs to be taken in the specification of the engine, transmission, axle, tires, and road speed combination of the entire vehicle.

Common Fleet Strategies

  • Fleets are increasingly investing in electronically controlled transmission, especially automated manual transmissions.
  • Many fleets have said that going forward all of their vehicles will be spec’ed with electronically controlled transmissions. 
  • Fleets have indicated these transmissions improve fuel economy but also help with driver recruitment and retention efforts.
  • In their recruiting efforts, many fleets tout the fact that their trucks have automated manual transmissions.
  • Fleet owners believe spec’ing electronically controlled transmissions makes them more attractive to younger drivers who have no experience driving standard transmissions.
  • In addition, fleets have reported that experienced drivers who may have been reluctant to try an automated manual transmission, end up having a positive driving experience and do not want to return to driving trucks with standard transmissions.
  • While there is not a great deal of data on resale value as many of the trucks with automated manual transmissions have not made it to the secondary market, fleets are confident that trucks equipped with automated manuals will not take a hit at resale time.

What Fleets Are Saying

Large Fleets

Executives from 19 large fleets were personally interviewed to find out about their experience with electronically controlled transmissions.

  • All of the fleets had experience with automated manual transmissions, but very few with automatics.
  • The fleets unanimously said that while at first their drivers did not like the automated manual transmissions, they later agreed that the technology has a positive impact on their work life.
  • Fleets were unanimous in the fact that they would try automated manual transmissions in the future. Many mentioned that automated manual transmissions are the choice for the future.

Michelin Fleet Forum

In conjunction with Michelin, the study team surveyed 200+ members of Michelin’s Fleet Forum about their opinions of electronically controlled transmissions.

  • According to one survey respondent, “[They provide] better efficiency and drivers actually like them better after they get used to them.”
  • Another survey respondent said, “With the new engines, automated manual transmissions improve mpg: in some cases up to 4% or better.”
  • “I like the idea of assisting newer and older drivers by removing the manual gearbox and clutch pedal,” said one survey respondent. “Additionally, if the claims of increased fuel mileage are correct, it’s worth investigating, since it would be easier to buy this equipment than try to force drivers to modify their driving habits.”

Decision-Making Tools

The study team developed several tools to help fleets in making their decision about electronically controlled transmissions. The Confidence Matrix is used to inform fleets of the study team’s confidence in the technology being studied vs. the payback a fleet should expect to receive from the technology. The Comparison Chart shows features of the various electronically controlled transmissions currently on the market.

Conclusions

After 25 years of development globally, electronically controlled transmissions are:

  • Are ready for prime time — These transmissions are proving to be reliable and adoption rates validate end user trust in their performance and durability.
  • Offer a good business case for adoption — They deliver fuel savings of 1-3%, have low operating costs and an acceptable initial purchase price.
  • Are an enabler of additional benefits — They allow further improvements in fuel economy, safety and operational efficiency especially as manufacturers combine highly integrated components into effective powertrain combinations.

Low Viscosity Engine Lubricant

In a truck’s engine, mechanical losses from pumping and friction consume approximately 16% of the total energy input of the vehicle. Lower viscosity oils—oils with less internal resistance to flow—will reduce these engine mechanical losses, thereby reducing fuel use.

Since 2003 fleets have been ramping up their investment in lower-viscosity lubricants. Yet while 40% of the largest, most efficiency-conscious fleets have adopted these engine oils, the adoption rates for the industry as a whole remain at only about 20%. However, new emissions regulations and the advent of new oil categories may increase the adoption rate.

Benefits

Fuel Savings

  • 0.5% – 1.5% when switching from 15W-40 to 5W/10W-30
  • 0.4% – -0.7% when switching to FA-4 oils, available after December 2016 from CJ-4/CK-4 5/10W-30 oils

Extended Oil Drain Intervals
Ability to extend oil drain varies, but one fleet expects to extended its drain interval by 20,000 miles.

Challenges

Cost

  • Increased costs for fleets using non-synthetic 15W-40 oils because most 15W-40 oils are mineral based and most low-viscosity oils are synthetic or synthetic blend
  • 30% to 40% cost increase when switching from a mineral-based to a synthetic-based oil

Compatibility with the Entire Fleet

  • Lower-viscosity 5W/10W-30 oil version of CJ-4/CK-4 is approved for engines going back only to model year 2010
  • FA-4 oils, which offer the greatest fuel efficiency gains, may have issues with backwards compatibility

Common Fleet Strategies

Case Study: National Truckload Carrier

  • Fleet age: 2 years
  • Average annual miles: 115,000
  • Operational region: Lower 48 states and Canada

The national carrier had been using a 15W-40 mineral-based oil. An oil supplier approached the carrier to test 10W-30 engine oil. The fleet agreed to the test to improve cold-weather starting and fuel efficiency.
The fleet anticipated a 0.5% fuel consumption benefit. It faced a significant cost increase but calculated it would earn an acceptable ROI as a result of the fuel savings.
Drain intervals were kept the same and in the two years since the switch the fleet has found no issues related to lower-viscosity oil.

Case Study: Carrier with Dedicated Operations

  • Fleet age: 2 years
  • Average annual miles: 80,000 to 100,000
  • Operational region: Lower 48 states and Canada

The national truckload carrier had considered switching to a 10W-30 oil. The fleet manager consulted with the engine supplier about available options.
Thirty vehicles were chosen for testing which included extending oil drain intervals. Oil sampling was conducted every 5,000 miles.
The fleet’s fuel testing indicated a reduction in fuel consumption of 1.5% to 1.8%. The fleet then rolled out the low-viscosity oil to its own maintenance facilities and at its offsite facilities.

What People Are Saying

Oil Companies

  • “Most people associate higher viscosity with better engine protection, but that sentiment is breaking down.”
  • “Most fleets and buyers of oil point to the viscosity as the primary identifier of an oil.”
  • “Studies that we have commissioned indicate that the on-highway segment is about 67% to 75% 15W-40 and about 20% 10W-30, with the percentage of 10W-30 increasing as the fleet size increases.”
  • “On the fuel consumption benefit of 10W-30 vs. 15W-40: “Own-truck testing indicates achievable improvements of ~1%. Span of improvements increases in applications with more stop-and-go.”

Engine Makers

  • “There is a quantifiable fuel savings with lower-viscosity oils in controlled engine tests. In most cases, the improvement is bigger when measured in the field. Field testing may exceed what we see in the test.”
  • On the reason for using 15W-40 vs. 10W-30: “People used to believe that the higher number is critical in determining engine protection. This is not true anymore.”

Decision-Making Tools

The study team developed three tools to help fleets make decisions about low-viscosity engine oil. The Confidence Matrix plots where the low-viscosity engine oil choices fall in terms of available data on the technology and how quickly fleets should realize payback. The Decision Guide can help fleets that want to benefit from the reduced fuel consumption offered by lower-viscosity engine oil. It describes the fleet’s current oil use and suggests what action a fleet needs to take.

Conclusions

  • Interviews and literature indicate that Class 8 over-the-road fleets can realistically expect fuel savings in the range of 0.5% to 1.5% by switching from 15W-40 to currently available 5W/10W-30 engine oil. The savings from switching to the fuel-efficient FA-4 variant, available after December 2016, is expected to be 0.4%-0.7% when compared to CJ04/CK-4 5/10W-30 oils.
  • All major North American engine OEMs have approved 5W/10W-30 engine oil for over-the-road applications. Approved oils, regardless of viscosity, meet the engine manufacturer’s requirements for engine protection.
  • Within the same viscosity grade, the base stock (mineral, synthetic, or synthetic blend) does not directly affect fuel consumption.

Direct Drive Transmissions

When a transmission operates as a direct drive, it sends engine input directly to the main shaft, eliminating parasitic gear mesh losses of power and fuel efficiency.

NACFE is not currently planning to further investigate direct drive transmissions, due to their simplicity. For more information, contact your transmission manufacturer on whether this technology is right for you.

Benefits

Fuel Savings
Direct drive transmissions eliminate the energy loss as power is transmitted through the extra gear in an overdrive transmissions.

Challenges

Compatibility with Duty Cycles
Direct drive transmissions work best for on-highway use on relatively flat ground. For fleets with other duty cycles or that run multiple duty cycles, direct drive transmissions may not be a good fit.

Resale Value


Synthetic Transmission Oil

Synthetic lubes and oils maintain their viscosity at low and high temperatures and have less friction and heat, which promotes energy efficiency and fuel economy. Significant improvements have been made on synthetic lubricants and increased scale is contributing to lower costs.

NACFE is considering a report on synthetic engine oil and other lubricants and additives.

Benefits

Fuel Savings
Less friction and heat promote fuel economy.

Stability at Higher Temperatures
Synthetic oil tends to have a higher viscosity index so it remains thick at high temperatures.

Longer Maintenance Intervals
Because of the improved oxidation and thermal stability of synthetic lubes, they are less likely to thicken as they age allowing for extended drain intervals.

Better Protection and Less Wear
The higher viscosity of synthetic transmission oil leads to less component wear.

Challenges

Initial Cost
Synthetic transmission lubes come with a higher initial purchase price but that can be offset by some of its benefits.

Availability on the Road
It may be more difficult to find these lubes when the truck is out on the road away from its normal supplier.


Gear-Down Protection

Gear-down protection delivers up to a 2% fuel economy improvement by encouraging drivers to stay in the top gear. This is one of the more promising engine parameters for improving fuel economy while not affecting the overall performance of the freight-hauling operation.

Gear-down protection delays gear down when climbing a hill, causing the truck to go at a lower speed but use less fuel. When the vehicle is in a gear other than top gear, the maximum road speed will be set lower than the allowed top speed. This encourages the driver to operate in top gear, allowing the engine to run at its most efficient operating range. The engine also can detect the vehicle load and will allow higher road speeds with heavy loads in lower gears to prevent vehicles from slowing down too fast in top gear. For gear-down protection to work properly, transmission setup and vehicle speed sensor features must be tuned correctly.

Confidence report coming soon.

Benefits

Fuel Savings
Delayed gear down when climbing a hill cause the truck to operate at a slower speed while using less fuel.

Challenges

Ensuring New Engines Have Correct Settings

Increased Complexity Maintaining Optimal Parameter Settings


Predictive Cruise Control

Predictive cruise control features use other data available on the truck to customize the speed in cruise control for other parameters. This is a growing area of interest of engine and truck builders for improving freight efficiency.

As terrain, congestion, wind speed, and other similar data become more available for the truck to “decide” the optimal speed, this technology can be exploited for even larger fuel economy gains.

Confidence Report coming soon.

Benefits

Fuel Savings
Predictive cruise control optimizes vehicle cruising speed which helps maximize fuel economy.

Challenges

Determining & Managing the Optimal Speed


Engine Downspeeding

Downspeeding is one of the primary powertrain-focused strategies for improving fuel economy in heavy-duty trucks necessitated by greenhouse gas emissions regulations.

With downspeeding the rear gear ratio is sped up in order to lower the speed of the engine, bringing fuel efficiency improvements. Downspeeding allows the engine to operate at the most efficient rpm while generating the minimal horsepower required to maintain a 65 mph cruise speed.

Benefits

Fuel Savings
Downspeeding can save 2% to 3% off of the fuel bill.

Improved Driveability
With downspeeding, the truck will have an AMT which results in smoother operation.

Reduced Noise
Due to the lower engine speed.

Challenges

Potential for Driveline Failure
Downsped axles, being less flexible, are much more sensitive to sudden shocks.

Greater Upfront Costs
Need to spec an automated transmission with a higher output torque capability, a certain clutch with a higher capacity damper, and higher torque driveshafts and rear axles.

Common Fleet Strategies

Downspeeding can be adopted in one of two configurations:

  • A direct drive transmission and a fast axle ratio The fast axle ratio direct drive transmission specification is optimal in terms of friction and fuel consumption reduction, but given the potential for driveline failure some manufacturers only approve it for true line haul applications where the highest torque conditions occur infrequently.
  • An overdrive transmission and somewhat slower rear axles. The somewhat slower axle ratio of an overdrive transmission spec subjects the transmission output, driveshafts, and axles to far less torque. This makes it appropriate for both line haul and regional and city delivery applications. An automated transmission should be spec’d on any downsped engine. If a manual transmission is selected, the engine’s torque response during clutch engagement must be specifically tailored to the drivetrain.

What People Are Saying

Drivers transitioning directly from a manual transmission to a downspeeding driveline must get used to not shifting and allowing the driveline to do the work. Of course, this probably is easier said than done for a driver who has upshifted, downshifted, and double-clutched for years. They must also adapt to the transmission shifting gears at engine rpms of approximately 1250 rpm instead of manual shifts at around 1800 rpm.” — John Moore, Volvo Trucks “An improvement of 3–6% is what you’ll see; I’m very comfortable predicting an improvement of 3%. When downspeeding is combined with other improvements in fuel economy-related aspects of design, fleets could reasonably be expected to see as much as a half mile per gallon.

– Aaron Peterson, Navistar

The trend toward engine downspeeding will continue to gain momentum as OEMs look for ways to further improve fuel economy.

— Andy Nieman, Dana Commercial Vehicle Technology

I hadn’t driven one of these new trucks in a few years and was amazed at how fun they are to drive! And it starts with how quiet they are.” — A major fleet manager “I was blown away by how it drove. In top gear, it would run down to 800–900 rpms, hanging in there very well. One advantage is that it’s very quiet, the engine is not roaring. Drivers like it. They worry about getting up to speed, and it does that okay. We’re not sure whether or not it does have the power to do the mountains, though.

— Phil Braker, Nussbaum Transportation

Decision-Making Tools

The study team developed a tool to help fleets in making their decision about electronically controlled transmissions. The Confidence Matrix is used to inform fleets of the study team’s confidence in the technology being studied vs. the payback a fleet should expect to receive from the technology.

Conclusions

  • Downspeeding is an idea that has been around a long time, but recent complementary technologies have made it more attractive and practical.
  • Fleets in long haul operation should consider downspeeding in their powertrain for improved fuel efficiency and driver satisfaction.
  • Some manufacturers are already at work on aggressive downspeeding with rear axle ratios at 2.28:1 or lower.

Fuel Additives

Fuel additives have been developed over the last decades with the goal of lowering fuel consumption. They modify the chemistry of the fuel with the resulting benefit of improved fuel efficiency. However, the trucking industry is generally skeptical due to past products’ results.

NACFE plans to study additives (potentially including hydrogen injection) as part of a full Confidence Report.  Please contact us if you can provide real world data to help sort out the products that genuinely benefit fleet operations.

Confidence Report coming soon.

Benefits

Deposit Control
Today’s fuel injectors are smaller and have tiger tolerances, fuel additives can prevent deposit formation that interfere with proper combustion.

Wear Prevention

Gelling Resistance
Diesel fuel contains wax and as temperatures drop the fuel can gel. Additives are designed to prevent this gelling from occurring.

Cold-Flow Protection

Challenges

Compatibility with EGR and SCR

Quality Control

Maintaining Chemical Balance of Fuel


Electrically Driven Accessories

Most accessories are either gear or belt driven by the engine; future components may be removed from the engine entirely If the electrical system can support their large energy requirements.

Benefits

Fuel Savings
If coupled with higher capacity and high voltage electric systems, there will be modest fuel savings.

Challenges

Not Available for Most Vehicles as of March 2017

Increased Complexity of Electrical System

Higher Electrical System Voltage and Power Output Required
Electrically driven accessories will add to the electric load on the vehicle.

Reliability Concerns

Increased Maintenance Costs

What People Are Saying

SuperTrucks

From 2009 to 2015, the Department of Energy sponsored a program with industry manufacturers to demonstrate at least a 50% improvement in freight efficiency. The project leads were Daimler, Cummins/Peterbilt, Volvo Trucks USA, and Navistar. Each of the four teams created demonstration vehicles incorporating a variety of new technologies to highlight the feasibility of meeting this aggressive goal.

As part of researching this subject, the NACFE study team interviewed each SuperTruck team to understand its analysis and choices relative to variable engine-driven accessories. It is important to note that most of the fuel economy and freight efficiency gains were achieved through improvements in aerodynamics, weight reduction, rolling resistance reduction, and powertrain improvements.

Note that all four teams chose to implement a form of waste heat recovery as part of their technology choices. The fuel economy gains for this technology are far higher than those available through improvements in accessory systems.

Fleets

On reliability: “The past few years have given us a lot of new challenges to manage due to the introduction of less-than-reliable new technology like aftertreatment systems or electric APUs. When it comes to accessories technology improvements, the new equipment must be proven reliable before I’ll be willing to implement it in my fleet across the board.”

On payback: “Any optional new technology that we implement must meet return on investment guidelines before it will be considered as part of a large purchase. Given that the fuel economy savings from new accessories are generally small, this makes measuring the potential improvement from anything new very difficult for us. This means it’s a harder sell to our management to make the investment

Decision-Making Tools

The study team developed several tools to help fleets in making their decision about electronically -driven components. The Confidence Matrix is designed to inform fleets of the study team’s confidence in the technology being studied vs. the payback the fleet should expect to receive from the technology. Technologies in the top right of the matrix have a short payback, usually thanks to their low upfront cost, and moreover are found to have enough performance data that fleets can be highly confident in those short payback times, usually because the technology is more mature or otherwise has a more substantial track record of results.

Conclusions

  • Fuel economy gains from currently available variable engine-driven accessory technologies are modest.
  • The payback for these devices is extended based on today’s fuel prices.
  • Duty cycle of each accessory is critical to the ROI calculation.
  • There is a significant concern for subsystem reliability of these new variable engine-driven accessory technologies.
  • Payback of many of the new accessory technologies is currently insufficient to result in high levels of adoption.
  • Future enabling technologies like higher vehicle system voltage, increased energy storage, and waste heat recovery will likely improve ROI of new variable engine-driven accessories.

Electrically Driven A/C Compressors

The A/C compressor aids the movement of the refrigerant for the cab air conditioning system. Although it only operates as required, sleeper compartments require A/C when the truck is parked.

The modern air conditioning system for vehicles includes a belt-driven, clutched compressor that takes power from the engine to drive a refrigerant through a closed-cycle system of heat exchangers and valves. The heat exchanger and refrigerant system are designed to remove heat from the passenger compartment of the vehicle and reject that heat through the air conditioning condenser coil that is located in front of the radiator.

​The only electrically-driven air conditioning compressors on the market now are ones used for battery APUs and ones that are installed on hybrid-electric transit buses. Currently, none are available or projected for standard on-highway vehicles.

Benefits

Fuel Savings
If coupled with higher capacity and high voltage electric systems, there will be modest fuel savings.

Challenges

Not Available for Most Vehicles as of March 2017

Increased Complexity of Electrical System

Higher Electrical System Voltage and Power Output Required
Electrically driven accessories will add to the electric load on the vehicle.

Reliability Concerns

Increased Maintenance Costs

To learn more, download the Variable Engine-Driven Accessories Confidence Report.


Variable Speed Water Pump

​Traditional water pumps constantly circulate coolant through a series of passages, cooling the engine components from the extreme heat generated through combustion and rejecting extra heat as the coolant passes through the radiator.

​New variable speed water pumps do not operate at full power all the time and therefore reduce the load on the engine. Managing pump speed through controls without compromising the cooling necessary reduces the overall horsepower required to drive the water pump.

​It is important to note that water pumps typically consume 1.1–1.8% of the truck’s fuel to perform their function, so any fuel economy gains from new technology will be modest.

Benefits

Fuel Savings (If Coupled with Higher Capacity and Higher Voltage Electrical System)

Challenges

Not Available for Most Vehicles as of March 2017

Increased Complexity of Electrical System

Higher Electrical System Voltage and Power Output Required

Reliability Issues

Increased Maintenance Costs

To learn more, download the Variable Engine-Driven Accessories Confidence Report.


Automatic Transmissions

Fleets should expect to see improved fuel economy from automatic transmissions, which have full power shifts and a torque converter to seamlessly transition between gears. They are most valuable in city driving where a significant amount of shifting is required.

Improved driver recruitment and retention are big factors behind many fleet owners’ decision to specify these transmissions over manual transmissions. In addition, they reduce the variability in fuel economy from one driver to the next.

Although it is too early to predict the payback for automatic transmissions, their business case is expected to be strong over time.

Note: All benefits and consequences are the same for automated manual transmissions (AMTs) and automatic transmissions except for the fuel economy performance. AMTs offer 1-3% fuel economy improvements and enable even higher levels of performance in future with features such as downspeeding, and the use of GPS to better manage hills and valleys. Fuel savings from automatic transmissions are yet to be determined.

Benefits

Fuel Savings
Because electronics are making the decision about when to shift gears, the truck shifts into the right gear when it needs to without driver intervention. Fuel economy benefits range from 1% to 3%, depending on other vehicle specifications and operating conditions.

Driver Recruitment & Retention
Many driver recruits have no experience operating vehicles with manual transmissions. Specifying trucks with automated manual transmissions enlarges the driver pool, which is a key advantage given the current driver shortage. Since these transmissions make the trucks easier to drive, drivers will be less tired at the end of the day, which should help fleets with driver retention.

Lower Driver Training Costs
Driver training time will be shortened because operating an automated manual transmission is less complex than operating a manual transmission.

Less Variability in Fuel Economy
AMTs decrease the variability in the fuel economy of trucks or drivers in a fleet, compared to the variability in fleets using manual transmission. Electronically controlled transmissions make poor drivers much better, average drivers better and good drivers slightly better.

Driver Performance & Safety
Electronically controlled transmissions improve driver safety because they allow the driver to concentrate on the road ahead rather than having to worry about shifting. The driver can keep both hands on the wheel.

Technology Enabler
Electronically controlled engines, transmissions, and other powertrain components offer the opportunity for improved and fine-tuned performance for various duty cycles and terrains.

Challenges

Higher Initial Costs
Vehicles specified with automated manual transmissions can cost as much as $3,000 to $5,000 more than similar vehicles with manual transmissions.

Resale Value
While there is not a great deal of data on resale value as many of the trucks with automated manual transmissions have not made it to the secondary market, fleets are confident that trucks equipped with automated manuals will not take a hit at resale time. Currently, automated manuals can bring $1,000-$3,000 less on the resale market, however most fleets have not yet traded their trucks equipped with automated manuals. Expectations are that residual values will be on a par with trucks equipped with manual transmissions.

Maintenance
Electronically controlled transmissions have more moving parts and require software to operate. As a result, fleets expect a small increase in maintenance cost.

Specification Issues
To get the most from electronically controlled transmissions, care needs to be taken in the specification of the engine, transmission, axle, tires, and road speed combination of the entire vehicle.

To learn more, download the Electronically Controlled Transmissions Confidence Report.

Engine Downsizing

Smaller engines can improve efficiency via lower weight and less friction as long as the duty cycle allows for the lower power.

North American heavy-duty over-the-road trucking has been predominately served by 15 liter engines for the past few decades. Much development has been made by the engine manufactures for this engine size.

Recently, 11 to 13 liter engines have been developed by each of the engine manufacturers and their performance is being optimized. Smaller engines might also assist in improved aerodynamics and underhood air flow since they take up less space. Powertrain integration can improve the effectiveness of these smaller powerplants.

Benefits

Fuel Savings

Weight Savings

Cost Savings

Challenges

Duty Cycle Limitations
Smaller engines are not appropriate for all duty cycles because they provide less power.

Resale Value
Selling a truck with a smaller engine may be more challenging.


High Efficiency Alternators

The alternator generates all the electrical energy stored and consumed on the vehicle. Today’s alternators use the engine to create electrical power both to recharge batteries as well as to power electrical loads while the engine is running.

Alternators are offered to the market in two efficiency ranges. The standard alternators generally have a maximum efficiency rating somewhere in the 55–60% range and the high-efficiency models are generally in the 68–75% range. These efficiency gains are mostly due to using conductors that allow greater fill of the windings in the alternator.

Versions that operate at higher efficiencies place less load on the engine.

It is important to note that alternators typically consume 0.5–1% of the truck’s fuel to perform their function, so any fuel economy gains from new technology will be modest.

Benefits

Improved Fuel Efficiency

Challenges

Limited Availability from all OEMs as of March 2017

Increased Costs

To learn more, download the Variable Engine-Driven Accessories Confidence Report.

Alternative Fuels

There are many fuel choices beyond traditional diesel and sustainability efforts are encouraging investigation of numerous other fuels. Infrastructure for natural gas has been improving and more alternative fuels vehicles are accumulating high miles.

Several companies are currently exploring Class 8 electric trucks and hydrogen fuel cells. Even a biodiesel dynamic blending technology is emerging.

Natural gas remains one of the foundational fuels of our alternative fleet, thanks to its ability to meet our diverse needs — especially the demands of the heavy-duty, over-the-road trucks that connect our regional hubs. These big rigs travel an average of 400 to 600 miles per day and require strong pulling power. CNG and LNG have proven to be the best alternatives to diesel for these trucks, meeting their required range and performance criteria while burning cleaner than diesel. Today, there are no other scalable, economical alternatives to replace a class 8 diesel tractor except for natural gas.

– Director of Maintenance & Engineering for Transportation Equipment for a Large Fleet

Introduction & Rationale

NACFE is fuel agnostic, and we are here to help fleets use less of whatever fuel they select.  Aerodynamics, lightweighting, tire rolling resistance, tire pressure, idle reduction and other technologies are a benefit regardless of what is in the tank.

Available Systems

  • CNG (Compressed Natural Gas)
  • Biodiesel
  • LP (Liquid Propane)
  • Renewable Natural Gas (RNG)
  • LNG (Liquefied Natural Gas)
  • Electric
  • Hybrids
  • Hydrogen
  • Renewable Diesel (RD)
  • Methane
  • DME (Di-Methyl Ether)
  • Others

Fuel Economy & Other Benefits

  • Range Anxiety: it is frequently one of the top issues for any alternative fueled vehicle as fleets are concerned about how far they can run before their next fill up.  The vehicle technologies researched by NACFE help improve the efficiency of virtually any fuel type.  More efficiency leads to Less Anxiety!
  • Legislative Compliance: The mayors of Paris, Mexico City, Madrid and Athens have proposed phasing out diesel delivery trucks in their cities by 2025.

Consequences & Challenges

  • Incompatibility: Sometimes a step forward in alternative fuels can mean a step backward in aerodynamics, idle reduction or other areas.  For instance, some natural gas vehicle storage tanks are not compatible with the chassis skirts and cab/sleeper aero extenders.
  • Fueling: Fueling infrastructure is commonly a challenge as the accessibility of trucks to oftentimes limited fueling stations is limited. There is a government website that illustrates the refueling station availability. The pulldown menu allows selection of several different fuel types including electric fast charging stations.
  • Facilities Requirements: It can be very expensive to convert a maintenance shop to handle natural gas or other alternatively powered vehicles.  It can also be challenging as standards for such facilities are not set and the fire codes and regulations are not universal.

Common Fleet Strategies

Many of NACFE’s key fleets, such as Frito-Lay and UPS are working heavily on alternative fuels utilization.

What People Are Saying

NACFE works closely with many organizations in the green space for commercial vehicles.  Find us at ACT Expo, Green Truck Summit, Midwest Green Fleets, DOE Clean Cities events and more.

GNA has published a report looking at leading alternative fuels options for medium-duty and heavy-duty commercial trucking entitled “The State of Sustainable Fleets 2020”.

BSR’s (Business for Social Responsibility) Future of Fuels initiative is helping fleets determine the best fuel choice for their business. See their approach and tools here at https://www.bsr.org/collaboration/groups/future-of-fuels.

Tools

Online fuel cost per mile comparison of alternative fuels:

  • ACT Research offers a Truck Fuel Calculator.
  • BSR’s Fuel Tool can help you make decisions on the fuel for each segment of your fleet.