Emissions regulations are playing a role in reshaping truck designs now and in the future
Never judge a book by its cover. The newest crop of Class 8 trucks on the market don't look much different than those offered two, five or even ten years ago.
But dig deeper. There are plenty of changes beneath the sheet metal. Take electronics, for starters. To control emissions yet still deliver optimum power, performance and fuel economy, the engine, transmission and axles on the truck are all linked together by hundreds of feet of wire and computers, commonly referred to as electronic control modules, or ECUs.
And it doesn't stop there. Brakes, stability systems, in-cab displays, and a slew of other functionality found on today's Class 8 tractor, regardless of application in most cases, all rely on the constant ebb and flow of data among a host of ECUs, all chirping away minute by minute, hour by hour, as these trucks log miles in good weather and bad, night and day, year after endless year.
“Everything relies heavily on electronics in today's truck,” says Landon Sproull, chief engineer forMotors Co. “There are probably anywhere from 10 to 15 ECUs on a commercial vehicle today, making sure, among many other things, that the transmission, engine and rear axles are all in sync, working together to provide the best fuel economy and performance.”
As a result, something that would seem as simple as a software update to these various ECUs must be approached with caution. “You must be really careful with the software running all these systems, especially when it comes to updates,” explains Sproull. “Because all of these systems are linked together, a software change to one component can have all kinds of repercussions upon the others. It's one of the things we as engineers keep a much closer eye on in our work, both now and for the future.”
This is also part of the tougher engineering challenges posed by product cost and capability. So the sticker price of trucks continues to rise, not only to cover the cost of meeting ever-tighter exhaust emissions regulations, but also for maintaining durability and reliability metrics required to make a truck last for the industry's unwritten standard of a million miles of operation or more.
“Both medium-duty and heavy-duty acquisition costs have increased as we move through subsequent emissions standards. In combination with some of the rules California is imposing, the biggest impact is felt on heavy-duty trucks and customers who run them,” explains Richard Shearing, director of product planning for Daimler Trucks North America (DTNA). “Our products must evolve to ensure profitable solutions for customers in the increasingly challenging times ahead.”
CHANGING TO STAY THE SAME
It's ironic that many of the rapid changes in commercial truck designs today are being done to keep current and future vehicle capabilities in line with past expectations.
“Customers are concerned about three major things when it comes to their trucks: fuel economy, weight and cost. And those concerns remain consistent,” explains Kevin Flaherty, senior vp-sales for.
As a result, says Flaherty, much of the ongoing research and development by OEMs focuses on ways to offset any changes to those three areas resulting from federal and state regulatory initiatives, from braking distance to emissions reductions, as well as general economic trends.
“That means looking at new materials to help take weight out, as well as the wider use of aluminum,” he notes. “Aerodynamic improvements also remain a focus, as is anything that improves fuel economy, simply because fuel is such a big cost to our customer's bottom line.”
Jerry Warmkessel,'s marketing product manager for highway trucks, points out that reduced weight and increased fuel economy are synonymous, so OEMs as well as customers are always looking for places to save weight without compromising durability.
“For example, customers are also looking at the volume of fuel they carry and realize that for every extra gallon, they are being penalized eight pounds of freight,” he explains. “We have one customer who has calculated that for every extra pound of the chassis, it costs them $15 at time of purchase. Therefore, a chassis that weighs 100 lbs. more than a competitor is already at a $1,500 disadvantage when comparing purchase prices.”
That weight issue really comes to the fore in terms of emissions control, whether the system used is advanced EGR (exhaust gas recirculation) espoused byor the selective catalytic reduction (SCR) technology being adopted by all the other truck makers.
“Obviously, the SCR emissions equipment has added the largest amount of weight, approximately 400 lbs.” says Warmkessel. “Customers will be faced with the choice of either reducing the volume of fuel they carry or lengthening their wheelbase to maintain current fuel quantities, and as a result, chassis real estate has become as valuable as waterfront property at the shore.”
Fortunately, he notes, SCR technology significantly increases fuel economy, anywhere from 3 to 5%, depending on vehicle application, so it partially offsets the additional weight of the required equipment.
Yet mitigating the weight increase from emissions systems is also driving other changes to all sorts of basic truck specs, such as engine displacement and rear axle configurations.
“The difference in weight between a 15-liter engine and a smaller 13-liter engine is 600 lbs.,” notes Peterbilt's Sproull. “Yet over the years, the horsepower and torque you can get from a 13 liter has been steadily increasing, so much so that a 13 liter can meet the power needs of most trucking applications, without shifting from a 10- or 15-spd. transmission either.”
“Many customers are finally paying attention to spec'ing only what is required to perform the task of their operation, as opposed to spec'ing high horsepower to simply satisfy their drivers' thirst,” adds Mack's Warmkessel.
Adding wide-base tires to a tractor's rear axles is another weight-saving tactic, he notes, saving upwards of 650 lbs. “There's a limitation, however, as it results in a 38,000-lb. rear suspension load,” Warmkessel stresses. “But for the customer who doesn't require more than [a rear axle load of] 38,000 lbs., it's a huge advantage.”
Even broader changes to tractor-trailer configurations are occurring as a result of the need to recover fuel economy lost to the demands of emissions control, says Jason Skoog, director of marketing planning and research forTruck Co.
“For 2010, we took a look beyond just the truck to the entire combination vehicle,” he explains. “As a result, we were able to close the typical gap between the trailer and tractor by 6 in. It doesn't sound like a lot, but at current fuel prices with a vehicle accumulating 120,000 mi. a year, shrinking that gap results in average fuel savings of $600 annually. That adds up over time.”
SETTLING THE SUBTLE SHIFTS
On another level, OEMs are making a host of subtle, smaller tweaks to their products to deal with what could be described as the ripple effects from larger changes, such as new braking distance regulations. Despite their size, the tweaks still require a lot of engineering work before they are successful.
Shorter braking distance rules issued by the National Highway Traffic Safety Administration (NHTSA) this past July mandate that a tractor-trailer traveling at 60 mph must come to a complete stop in 250 ft., versus the old standard of 355 ft.; roughly a 30% reduction in truck stopping distance. In addition, this final rule requires that all heavy-truck tractors must stop within 235 ft. when loaded to their “lightly loaded vehicle weight.”
Though this new regulation is going to be phased in over four years beginning with 2012 models, NHTSA said three-axle tractors with a GVWR of 59,600 lbs. or less must meet the reduced stopping distance requirements specified in this final rule by Aug. 1, 2011. Two-axle tractors and tractors with a GVWR above 59,600 lbs. must meet the requirements specified by Aug. 1, 2013.
Ramin Younessi,'s group vp-product development and strategy, says retooling trucks and trailers to meet those new rules isn't particularly difficult. For the first phase at least, he says all that will be required are larger drum brakes to produce more stopping power.
The real trick to this, however, comes from managing how that higher brake torque affects the vehicle's suspension system, especially the front suspension, while at the same time ensuring that the greater brake power does not alter the “feel” of the truck for the driver.
“You not only want to make sure the stability of the vehicle isn't affected by the application of greater brake force; you want to make sure there's no difference in handling or feel for the driver in a stopping situation,” Younessi explains. “By that, we mean no unexpected vibrations or dropping of the truck's ‘nose,’ or anything like that. That's where the really subtle engineering takes place.”
“For the most part, drum brakes will handle the change, with associated systems being validated to determine if any additional changes will be needed,” adds Frank Bio, product manager-trucks forTrucks North America. “This includes suspensions, axles and brake components, including lining — and we expect a change in lining — and the addition of brake shields as a method to meet the test requirements. This does not eliminate the need for disc brakes in certain configurations; but for the first phase, we expect [drum] brakes to handle the requirements.”
Bio adds that by keeping drums as the foundation for the vehicle's braking system, this will help fleets on the cost end of the equation to a degree, as those maintaining their own equipment won't need to retrain staff or stock new parts to handle disc brake systems.
He stresses that it's critical such changes go unnoticed by drivers. “The vehicle's stopping characteristics must stay the same. They must stop in a shorter distance, obviously, but drivers shouldn't notice anything else, such as a different feeling in the steering wheel or brake pedal,” Bio points out. “When drivers go from an older truck to a newer model equipped with more powerful brakes, they should expect it to respond the same way.”
It's all part of what Bio terms an ever more “complex juggling act” OEMs must engage in to provide trucks to fit the needs of customers.
“We are just seeing more and more refinement of trucks today, even with a customer's fleet or specific application,” he says. “We are seeing a huge amount of smaller changes too, especially on the vocational side, regardless of whether fleets plan to use SCR or not. It's literally getting to the point that within individual customer fleets, we're finding they want to spec trucks for East Coast operation very differently from those earmarked for West Coast operations. In trucking today, just one type of truck won't do it.”