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August 25, 2012

Driving the 2014 Cascadia Evolution

When it’s available early next year (ordering is open now), the 2014 model-year Cascadia Evolution from Freightliner will offer revisions to Cascadia’s already extraordinary aerodynamics, changes to the common-rail fuel system and a simpler turbocharger setup, which should deliver a 7% fuel savings for the “new” Cascadia. Another significant option is the soon-to-be-available Detroit DT12 automated transmission.

This demonstration unit had more available fuel economy technologies to achieve a test-track 10.67 mpg. To further demonstrate available fuel efficiency, the same truck was employed in an over-the-highway Evolution of Economy Tour, a real-world highway run from San Diego, Calif., to Gastonia, N.C. That truck and driver combo scored 9.31 mpg to prove the updates to the Cascadia could push fuel economy close to the magical 10 mpg.

The truck
Changes to the Cascadia to boost aerodynamic efficiency were developed in Freightliner’s own wind tunnel in Portland, Ore. Many of the detail improvements are around the front fascia, with hood and bumper closings to keep air flowing around to the sides and there’s a change to the air dam under the front. A smaller radiator allows less air through, saving some weight as well. Other aerodynamic improvements include subtle change to the windshield seal, a sleeker elliptical shape for the mirrors and an integrated antenna. New chassis fairings and longer side extenders contribute to the lowered drag.

The resized radiator is a result of the switch to selective catalytic reduction, which requires less cooling for the still-present EGR on the 2010 DD engines. But at the same time, the new radiator has a revised baffling system for greater efficiency and a new mounting for increased durability.

Those are the basic Evolution changes. But the truck I drove was the ultimate Evolution, with 6x2 drive, ultra-low profile single tires, wheel covers and a trailer with aerodynamic aids created in the Freightliner wind-tunnel but representative of commercially available products. It also had the new Detroit DT12 transmission. Suffice it to say, the electronic controls and the way the transmission talks to the engine make this the ultimate in optimization, for performance and economy.

In this Evolution, the direct transmission is backed up by a Meritor final drive of 2.50:1 in the single drive axle. The tandem is the available Meritor 6x2 setup with a forward drive axle. A loading valve and anti-spin logic provide added traction when needed. It is gaining increasing attention with the 400-pound weight savings and the additional fuel economy from only one set of gears driving.

The ultra-low profile singles on tractor and trailer are by Michelin. They’ve been in the marketplace for 10 years, with more than a million produced. That should be enough to convince anyone they work. And not one went flat on this truck’s coast to coast run. They are as likely as not a major contributor to the outstanding coast-to-coast mileage. Fleets that use them consistently turn in leading fuel economy numbers, and there’s no question that they contribute to fuel economy.

Another fuel economy feature on the evaluation unit is the wheel cover. Developed by Jon Fleck, they really do the job. Easy to fit and work around, they actually deliver a modicum of fuel savings. A modicum here, and a modicum there, and you have a nearly 10 mpg truck.

In the cab
It’s great to climb aboard a really nicely spec’ed cab and sleeper, and this one truly is, though for the sort of application likely for this truck, the dinette sleeper would be my taste. Be that as it may, the 2014 model is little different from the tuck we tested earlier this year, except in dash and controls.

The dash now includes a new instrument cluster with gauges in the speedometer and tachometer, making use of otherwise underutilized real estate. It puts the coolant temperature and oil pressure gauges right there where you want to see them along with a repositioned fuel/DEF gauge. There are in-wheel switches for engine brake and cruise control, and marker light interrupter and flasher. And there’s the new shifter control on the steering column for the Detroit DT12 transmission. 

A new switch sets the soft cruise setting the driver feels is most appropriate to his driving style.

On the road
We were fully loaded sitting in a turnout at Yountville facing southbound through the Napa Valley on state 29. It was hot outside but the 2014 Cascadia Evolution was nicely cool in the cab. The main reason for the drive was to explore the features of the new transmission while negotiating I-80, some divided highway and then some two-lane through the town of Napa and back through the vineyards of the region.

Starting out, with a foot planted on the service brake I rolled the direction selector to Drive and leaned on the air valves to release the brakes. All there remained to do was to move the right foot and squeeze down on the throttle. There's no danger of rolling back as there is a creep and crawl feature that will give a slow forward motion even without touching the accelerator. For steeper hill starts a hill-hold feature commanded by the transmission keeps service brakes applied until a torque sensor tells the air brakes to release.

For medium to heavy pedal demand, the transmission responds well, choosing the right gear for the conditions – including the truck weight, which for us was 76,000 pounds – and skip shifting for the quickest or the most economical acceleration. For instance, in one sequence in Economy mode and moderate throttle, the transmission shifted 2, 3, 5, 7 and 8 within about 50 yards.

In the upshifts, there is interaction between the transmission and the engine retarder. The advantage is to punch the shift through as quickly as possible and also to minimize the torque break during the shift. Thus the truck slows less during the shift. Since there is less roll-off of speed, the feature actually saves some fuel – minute maybe, but still a savings. From a driver’s perspective, it enhances the performance – and remember we are still in Economy mode – to get up to speed faster.

Driving in Economy mode, where there is a need for additional performance, there is a kick-down feature at the throttle pedal. You can feel it in action as there is a detent that the driver has to push through, which produces a down shift followed by rapid acceleration from the 455-hp DD15.

In Economy mode, I noticed shifts for the most part between 1425 and 1450 rpms, putting the revs in the next gear precisely on 1000 rpm to make use of the flat 1,550 pound-feet from the 455-hp DD15 of the evaluation truck. In the performance mode, revs drift up to 1600 to 1700 and after an upshift the engine is at 1,300 rpm, where it can make best use of the horsepower curve.

This outbound stretch of highway has regular traffic lights, all seeming to turning red as we approached. But that was no problem: pulling down a notch or two on the shift lever for the retarder. As a bonus, the system is sensitive to how much braking is demanded. In the third (Maximum) demand position, an aggressive downshifting regime brings downshifts to make the retarder work at its peak efficiency.

But even without this feature, as you slow for a light or a corner, the transmission downshifts to be ready for the next acceleration demand.

One of the coolest features is the e-Coast, where the transmission goes to a neutral and the rpms fall to idle when cruise detects no throttle to retain road speed. Truly remarkable is how frequently this feature comes into use. On the rolling highway of I-80 West and East bound, I was astounded to be in and out of e-Coast all the time. On the coast-to-coast Tour early in the year, when this truck scored 9.3 mpg for the trip, the e-Coast mode accounted for around 25% of the total running mileage.
New for the 2014 is an asymmetric, waste-gated turbocharger for "fleet" horsepower ratings like this 455. By dispensing with the turbo-compounding on these lower rated engines, there is an economy gain and a savings of around 100 pounds. Despite this, there is plenty of performance on tap, helped in part by the efficiency of the transmission. Higher power ratings 15-liter and DD 16s will still feature the turbocharger

It was hard to imagine how the Cascadia could be improved, it was such a game-changer when it was introduced. But put the new transmission in the Evolution, spice it up with some added aerodynamic aids for the trailer, and you’ve got a package that delivers near magical 10 mpg fuel numbers with the ease and repeatability of the automatic shifting. It’s a combination that’ll be very hard to beat.

August 24, 2012

Detroit's New Automatic is a Fuel Saver

The automated 12-speed transmission from the Detroit brand of Daimler Trucks N.A. was rolled out in August. It's the latest automated transmission introduction to the N.A. truck market, with calibrations and programming new for the North American operating environment. However, the mechanicals within the transmission have been well proven in millions of miles and over a hundred thousand Mercedes-Benz cabovers in Europe and other world markets, often at far higher gross combination weights than our 80,000 pounds. The transmission will be available in the Freightliner Cascadia Evolution starting in May 2013.

The Detroit DT 12 is a three-speed main transmission with a range-change and hi-lo splitter to give 12 forward speeds and an available four speeds in reverse. The single countershaft and aluminum casing give it a weight advantage of 100 pounds compared to Freightliner's existing offering – the Eaton Ultrashift Plus – which will continue as a second automated transmission option. The first Detroit DT 12 transmission is the DA1750 direct rated 1,750 pound-feet and the OA2050 overdrive at 2,050 pound-feet. It will be the larger of a pair of transmissions: later in 2013, the lighter B transmission DB1550 and OB1650 with input torques reflected in the model designations will be available with weight savings of 680 pounds compared to the Eaton.

According to the company, the DT 12 has a number of features and some significant benefits compared to competitive transmissions, with the shifter the most apparent. This is a steering column-mounted shift stalk, though somewhat more robust than the usual column stalk. It’s a convenient alternative to the visually unappealing dash-mounted shift pad. Like the pad, though, it doesn’t impede a driver's passage through the cab or into the sleeper.

In use, the DT 12 can be operated in automatic or manual. In either case, pulling the shifter up towards the wheel initiates upshift; pressing away, downshift. In the end of the lever is a switch to allow users to select Auto or Manual mode, or a quick touch selects Economy or Performance shift schedule. This same column shifter is also the selector for the engine retarder, with off, two, four and six-cylinder brake application as the lever is pulled down through four detents. Forward, reverse and neutral are selected with a rotary switch embedded in the shifter. A neat feature is a neutral reminder and selector if the driver forgets to take the transmission out of a drive position while setting the brakes and keying off.

With the MT 12, there are new features for the cruise control. One is a dash-mounted switch that allows for selection of different levels of "float" in the cruise setting. In low, it will allow speed to gain 3 mph before cruise control applies the engine brake. On medium, it allows twice this margin before application. In the highest position, it removes all interaction with the truck speed, allowing the truck to roll and take maximum flat or mildly rolling terrain.

Another feature designed to improve fuel economy is eCoast. This senses when the truck is rolling on any kind of a downgrade and drops engine torque to zero. The transmission then goes to neutral and the engine speed drops to idle. While this may be considered a little-used feature, in the recent coast-to-coast economy demonstration Freightliner, the demonstration truck was in e-Coast mode for 25% of the mileage covered, accounting for significant fuel savings.

At the other end of the performance spectrum, there is a throttle kickdown switch where a detent is provided in the throttle movement. Punching through this causes a downshift and a change to the fueling schedule so acceleration is akin to the transmission being in performance mode.

In the different shift modes, the transmission will upshift at 1400-1450 to drop back onto peak torque at 1000 rpm; in performance mode, shift points are higher to get the engine into the higher horsepower, shifting at 1700 rpm or more, depending on conditions the transmission recognizes, such as grade, throttle demand, gross vehicle weight and so on.

Upshifting, there is interaction between the transmission and the engine brake. With the proprietary interface, the electronics do a lot more than just speed the shift. Initially, the retarder aggressively reduces engine speed but then as engine speed approaches synchronous between gear and road speed, two cylinders start to fuel even if the other four are still in retarder mode. This keeps the turbocharger spooled up and when the upshift completes, the engine is sooner on power in the next gear. The advantage of this sequence is to punch the shift through as quickly as possible and also to minimize the torque break during the shift. Thus the truck slows less during the shift. Since there is less roll-off of speed, the feature saves more fuel.

Another feature of the advanced communications is driveline protection – the transmission senses engine torque applied and will dial it down to prevent wind-up in the driveline. This protects the drivetrain and provides a more comfortable driving experience, according to Detroit.

The new transmission also has Daimler’s Virtual Technician, the on-board diagnostics and prognostics feature that detects fault codes and transmits them behind the scenes to the Customer Support Center. Service decisions are then based on the nature of the fault code, the mission of the truck and the availability of dealer support.

With implementation of the new automated transmission, there's a new dash display for Cascadia in 2013 that is currently referred to as IDB4. It includes information about the gears selected as well as up and down arrows for shift advice when in manual mode. It also indicates whether the transmission is in Performance or Economy mode. There is also a dash warning light that illuminates with a fault code and activation of Virtual Technician.