Fine-Tuning A Favorite
Freightliner brings its Cascadia up a notch with Evolution
By Paul Abelson
A few years ago, Freightliner introduced the Cascadia. Developed in the company’s wind tunnel in Portland, Ore., it was touted as the most aerodynamic — and therefore fuel efficient — conventional tractor ever.
That claim was challenged immediately by Navistar, which argued that its International ProStar deserved the honor. Spec for spec, the two trucks were about equal. But since then, new tractors have been introduced by Kenworth and Peterbilt and current models were tweaked by Mack and Volvo. Aerodynamics play a big part on all of them. So Freightliner did some work to make sure they retained their standing. The result is the Cascadia Evolution, to be introduced next year as a model year 2014 truck. Its refinements result in as much as 7 percent better fuel economy than the EPA 2010 compliant Cascadia.
Small changes make an impact
Some of the evolutionary steps seem minor but taken together, the results are impressive. Something as seemingly small as relocating all the antennae inside the roof fairing eliminates a source of turbulence. Changes were also made to the windshield seal and the hood-to-bumper closure. The bumper itself had the center section filled-in and smoothed over, while an air dam was fitted below to help manage under-body air flow. The opening for the 1,400-square-inch radiator was redesigned to help smooth under-hood air flow.
Some of the larger modifications include longer, deeper side fairings and 20-inch cab side extensions. Even the mirrors were redesigned with an elliptical shape that better manages air in that high-turbulence area. Another aerodynamic enhancement is an optional set of wheel covers for drive wheels. They can also be fitted to trailer tandems for about one percent added mpg.
But aerodynamics alone would not yield the fuel efficiency that the Evolution achieved. The truck I drove had a Detroit DD15 engine rated at 455 hp with 1,550 pounds-feet of torque at a low 1,000 rpm. Power is transmitted through a brand new DT12 automated manual transmission to a single drive axle in a tandem configuration. It’s referred to as a 6 X 2, six wheel positions but only two drive wheels.
The configuration saves about 400 pounds overall. Drivers in North America prefer 6 X 4 setups for better traction, but Freightliner applies electronics to limit wheel spin of the wide-base single tires. The final drive ratio is only 2.50 to one for an optimal balance of economy and engine rpm operating range.
Integrated electronics are a major factor in the Cascadia’s fuel economy and its ease of operation. Daimler Trucks North America includes Freightliner and Western Star Trucks and Detroit engines, running gear and the new 12-speed automated manual transmission. An integrated manufacturer can have all on-board management systems communicate with each other.
So the engine and transmission computers work together, but also incorporate engine braking for quicker shifts and suspension management to improve traction control. Even GPS navigation data comes into play to enhance Daimler’s advanced cruise control. The GPS data determines elevation changes up to one mile around the truck. Then the fuel management system, transmission and the engine retarder use that information to adjust speed according to what is needed for the optimal balance of control and fuel efficiency. It shifts from drive to coast mode to brake mode, varying speed by as much as six mph.
Set on “Off,” the engine brake is disabled when in cruise control. That’s for flat terrain. “Medium” is for rolling hills. It lets the engine brake hold speed to +6 mph. “Low” is for steep grades, limiting overspeed to +3 mph.
Taking it to the streets
In the high traffic, multiple stop light flat terrain area where I did my test drive, there was no opportunity to play with Advanced Cruise Control. But the DT12 transmission was quite impressive, especially when mated to a fleet-spec’d engine.
When truck makers provide their latest models for us to test, we often get high power, high torque engines. I’m comfortable with 500 horsepower or more, usually with 1,850 pounds-feet. But here was the Cascadia Evolution with “only” 455 hp and a trailer loaded with enough concrete to bring gross combination weight to 78,000 pounds. My expectations for spirited performance were not very great.
In back, the sleeper portion was tried-and-true Freightliner with a traditional layout and fairly nice trim. It was the front, however, that impressed me. The dash had attractive wood grain trim accenting the rich-looking, softly textured surfaces. Instruments are functionally grouped and easily visible behind the multi-function steering wheel. Reminiscent of a luxury car, the wheel houses controls for headlight flashers and marker light interrupters, cruise control and the engine brake.
Just to the right of the wheel within easy reach is the shift control stalk for the DT12. It has settings for manual or automatic operation. In manual mode, the driver moves the control forward or back to shift gears. A cylinder in the stalk rotates to change drive direction to forward, neutral or reverse. The shift lever also sets the engine retarder. When maximum is called for, the computers alter shift points to provide maximum braking.
Starting out was easy. With my foot off the throttle, the transmission went into creep mode as soon as I released the brakes. It held a steady speed, around 2 mph, until I pressed the pedal. Accelerating slowly, the transmission skip-shifted quite a bit, sometimes jumping three gears.
Creep mode works in reverse, too. It makes backing into docks much easier and safer. Once in traffic, I wanted to move away from traffic lights, so I pressed the pedal farther. That brought more rapid shifting with fewer skips.
The net result was rather brisk acceleration that was more than I expected or even hoped for. A few times when at speed in cruise control, I noticed the transmission shift to neutral and the engine rpm drop to idle. This is the “coast” mode that cuts the engine back when there is no demand for power. It usually happens on slight downgrades. On steep hills or when the retarder is on, this fuel-saving feature is off.
Additional safety features include Hill Start Aid and Auto Neutral. When stopped on a 6 percent or greater hill, the truck is prevented from rolling when the brake pedal is released. It works in both forward and reverse. Auto Neutral shifts to neutral when the parking brakes are set, but the transmission is left in gear.
Selecting Automatic or Manual mode allows the drivetrain to operate normally, with either the computer or driver managing the shifting. Performance mode lets you get the most power out of the engine, while Eco mode keeps the engine operating as close as possible to the sweet spot, the engine speed where fuel economy is greatest.
Pedal Kickdown lets drivers increase downshifts for acceleration for hill climbing or more rapid passing, no matter what mode is set for the vehicle.
The truck rides comfortably and turns easily. Vision is good all around. Of course, Freightliner got these things right in the first iteration of the Cascadia, so there’s no reason to think the Evolution would offer any less.