Your transmission can see the future, and the future is fuel efficient

Your transmission can see the future, and the future is fuel efficient

Kenworth-Predictive-Cruise-Control

It’s a scenario a driver runs into repeatedly—the truck turns a corner and comes across a steep hill. The driver puts the pedal to the floor, burning excess fuel in an effort to remain at a reasonable speed as the truck climbs. Upon reaching the top, the truck careens down the hill at an excessive speed, necessitating overuse of the brakes.

That scenario can be a thing of the past thanks to recent truck powertrain technology: predictive cruise control systems. Introduced to the market only a few years ago, these are now a staple of the offerings of each major truck OEM.

“In the simplest sense, predictive cruise control utilizes a truck’s momentum in rolling hills to help save fuel,” says Allison Athey, product marketing manager of transmissions with Volvo Trucks North America.

PACCAR MX-11

Let’s dig into the details of what makes predictive cruise work. Predictive cruise control systems use GPS data, onboard maps and cruise control to optimize cruising speed based on the topography of a truck’s route. As the truck enters certain types of terrain, such as rolling hills, predictive cruise control looks at engine torque, gear, grade, hill profile and cruise settings to select the correct gear to approach the approaching terrain.

Rather than burning excessive fuel going up the hill and then rolling down the hill too fast, the system anticipates the hill and sets the truck up for the ideal way to approach it. This saves fuel by using the truck’s momentum to navigate the hill, rather than its fuel. The truck’s engine and transmission work together to predict the route and set the truck up to handle it in the best, most fuel-efficient way possible.

“It’s similar to riding a bicycle,” says Jim Nachtman, product marketing manager for on-highway trucks with International Trucks. “When you’re on flat terrain and the system recognizes a hill coming up, the vehicle will speed up slightly, so that you get a little bit more momentum at the base of the hill. It makes it easier to go up and over the hill. As you go up the hill and you get closer to the top, the system allows the vehicle speed to drop to below the set cruise control speed. The truck crosses the hill at a little bit lower speed. When you go over the top of the hill and start to go down the back side, the transmission shifts into neutral—the engine is just idling—and the vehicle coasts down the back side of the hill.”

The speeds at which the truck approaches the hill, with the help of predictive cruise, can be pre-set by the fleets. Nachtman explains that if a driver set the predictive cruise to 62 MPH, the fleet could set a threshold between plus 5 MPH and minus 3 MPH, for example.

The offerings

All of the major heavy-duty truck OEMs offer predictive cruise on various models in their long-haul, on-highway segment. These predictive cruise control systems function similarly, but their processes can differ.

In terms of fuel efficiency, improvements vary based on the truck and the route it runs, but each truck manufacturer has an estimate of what a typical fleet can expect to save. Keep in mind that predictive cruise provides the greatest benefit in hilly terrain, so the more hills there are on your route, the more fuel you’ll save.

Daimler’s Detroit engine’s predictive cruise system is known as Intelligent Powertrain Management (IPM) and works closely with the Detroit DT12 transmission, says Kelly Gedert, manager of powertrain and components marketing with Daimler Trucks North America.

“IPM uses shifts, acceleration, engine braking and coast versus eCoast optimization to efficiently operate the powertrain and thus improve fuel economy,” Gedert says, adding that the system can see what’s coming 1.2 miles or more down the road.

“To move from a vehicle that does not have Intelligent Powertrain Management to a vehicle spec’d the same with our latest version (IPM4), a customer can see up to 3.2% fuel economy savings,” Gedert relates.

International offers its predictive cruise system as an option for its RH and LT series trucks. “If you’re operating in a predominantly hilly terrain,” International’s Nachtman says, “you’ll see a fuel economy savings of up to about 2%. And all the major roads in US & Canada are preprogrammed into the PCC system, so the system does not need to learn the terrain to deliver improved fuel economy.

“Interestingly,” he adds, “the majority of the fuel economy benefit with the predictive cruise is actually achieved going down the hill. When you’re going down the hill, the system also has control of the engine brake. It knows how much mass is in the vehicle and how steep the grade is. For example, if you’re going down a long grade with a heavy load, it’ll apply the engine brake earlier so that it minimizes the use of service brakes as you get towards the bottom of the hill. Conversely, if the vehicle is bobtail or has a light load, it may wait significantly longer to apply the engine brake because it knows it has plenty of brake power to control the speed safely.”

Earlier this year, Kenworth announced an update to its predictive cruise control functionality, which it offers for the Kenworth T680 and T880 with the 2017 PACCAR MX-11, PACCAR MX-13 and Cummins X15 engines.

“This update, which was made in conjunction with the launch of the new 2017 emission engines, provides our customers up to a 1% improvement in fuel economy over the performance of the current version of our predictive cruise control,” says Patrick Dean, Kenworth’s chief engineer.

Mack predictive cruise works closely with the company’s mDrive transmission, notes Scott Barraclough, Mack’s technology product manager. “It does not require a constant GPS connection—after a short connection to GPS, Mack predictive cruise recognizes the hill, sends the communication to the mDrive transmission, which automatically knows the optimal speed and gear strategy for the upcoming terrain,” he says. “Because the hill is stored in the vehicle’s memory, predictive cruise recognizes it and knows when the gradient will even out, allowing the truck to maintain its speed for the next hill. It operates completely automatically and requires no input from the driver.”

According to Barraclough, fleets using Mack predictive cruise can expect up to a 1% improvement in fuel efficiency.

Peterbilt offers predictive cruise control on Models 579 and 567 when spec’d with PACCAR MX engines, says Wesley Slavin, Peterbilt’s marketing manager for on-highway vehicles. The 2017 release of predictive cruise control on the MX engine provides additional fuel economy improvements of up to 3% on Peterbilt Models 579 and 567, he adds.

Volvo’s predictive cruise system, known as iSee, generally provides fuel savings of about ½%, according to Athey. “The benefit is much greater when operating in rolling hills, and we’ve seen savings of up to 3%,” she adds.

Eaton’s Neutral Coast Mode

Eaton Ultra Shift Plus Transmission

Eaton’s Neutral Coast Mode feature is aimed at maximizing vehicle momentum by disengaging the driveline and bringing the engine to idle when appropriate in a drive cycle.

“This mode is enabled at cruise speeds when the driver demand torque approaches zero,” explains Alex Stucky, global product strategy manager for heavy-duty linehaul transmissions with Eaton. “The transmission recognizes these entry conditions and prepares to disengage the driveline. As that driver demand torque reaches zero, meaning the engine is effectively under no load, the transmission shifts into neutral.”

Neutral Coast Mode allows the transmission to disengage the driveline by pulling out of gear on downhill grades where little or no engine power is required, when the vehicle is in cruise control and the transmission is in drive mode. The vehicle’s display will then flash the gear number that the transmission will select when it is necessary to engage.

The transmission will then exit Neutral Coast Mode under any of the following conditions:

  • Vehicle brakes are applied;
  • Driver presses accelerator pedal;
  • Cruise control is canceled;
  • A mode other than drive is selected;
  • Cruise high or low set speeds are exceeded;
  • Maximum vehicle grade is exceeded; or
  • A request by an adaptive cruise system.

Stucky says that trucks equipped with predictive cruise control will be able to make more efficient use of Neutral Coast Mode.

“Vehicles equipped with predictive cruise control can share data with the transmission, which will allow a more intelligent decision on coast mode. In a given duty cycle, you’ll have more opportunity to coast, reduce shift density, and in most duty cycles, better fuel economy,” he explains.

Eaton offers the mode as an option for all linehaul automated transmissions. “It’s duty-cycle dependent, but on a broad range of duty-cycles, we’ve seen around a 1% fuel economy improvement in linehaul applications with neutral coast,” Stucky says.

The future

Detroit-Integrated-Powertrain

Predictive cruise is a relatively new offering in the heavy-duty world, so we can only speculate as to what future versions of the technology will look like. Nachtman says that International’s engineers are looking at a second generation of predictive cruise control now.

“Some of the ideas that have been discussed include more integration with the rest of the vehicle accessories,” he says. “For example, if you’re going up a long hill, you may get into a derate condition to control coolant temperatures, perhaps the system would turn the fan on earlier to cool off the engine and lessen or eliminate derate altogether. Similarly, it would also reduce air conditioning use going up a hill, so that you have more power available. Going down the hill, it may turn the HVAC system to a higher setting to get better braking performance and more fuel economy savings out of it.”

“The opportunity really exists to expand the coasting capability to squeeze more fuel economy out of the feature, and some of that will be enabled by more data on the vehicle,” Eaton’s Stucky says. “From the predictive and map data, the update rates and sheer resolution of the look-ahead data increases the opportunity to coast, both in and out of cruise control. So if we look a little further ahead, I think there’s more opportunity to improve function and fuel economy further. I think that we may see some prototyping of engine-off coasting features. I also think, as we see more steps towards advanced driver systems, we’ll continue to partner with the OEMs on the integration of those systems to improve drivability and fuel economy, and the predictive and neutral coast features are a big part of that integration.”

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