TEST DRIVE: VOLVO I-SHIFT
Volvo’s new automated-manual transmission, I-Shift, will blow drivers away. It will do anything you want it to, or it will manage the shifting all on its own — depending on how you choose to drive it. This is a driver’s transmission, but it will please the truck’s owner too. Its default is programmed for economy, but the driver can get performance out of it in a very natural and intuitive way. Volvo launched I-Shift in late September at an event in Savannah, Ga., where a bunch of motor-noters had the chance to drive it. We were offered a few laps on a closed track to get a feel for it, and that was just enough to whet the appetite. Two aspects of this transmission really set it apart. First, the transmission’s electronics: Volvo optimized the I-Shift for use with the 2007 D11, D13, and D16 engines by programming each of the engine’s fuel maps and performance curves into the transmission. This high level of integration allows the transmission and the engine to calculate optimum output with appropriate gear selection to achieve the best possible combination of fuel economy and performance. In other words, the two perform as one. There’s a lot more to this, but we’ll get there in a minute. The second thing that sets this transmission apart is the clutch arrangement. It’s a two-pedal set-up with a single-plate clutch engaged by an electronically controlled air-over-hydraulic actuator that takes its cues from the throttle pedal position at launch. This feature is particularly helpful when backing. If you just want to inch back, instead of slipping the clutch as you might do in a manual set-up, you just feather the throttle pedal. As you press the throttle down the clutch engages very smoothly and away you go — just like in a manual, only better. This one feature improves drivability dramatically. The clutch is used on every shift. The Hardware The 12-speed I-Shift is a single counter-shaft, three-speed gearbox with high and low ranges and a two-speed splitter for each gear. The two reverse gears can be shifted on the fly, giving drivers more flexibility while backing. It’s available in direct or overdrive (0.78:1) with an overall ratio of 14.94:1 in direct and 15.04:1 in overdrive configuration. It’s a full-manual gearbox with an electronically controlled X-Y shifter mechanism. The driver interface is a seat-mounted shift knob with a triggerstyle selector for manual shifts. There are three driving modes (forward manual (M), forward automatic (E), and reverse (R). The knob toggles between the three positions. There is also an economy/performance selector so the driver can choose how the engine shifts. In ‘E’ mode, the transmission will select shift points and engine parameters to maximize fuel economy. In ‘P’ mode, gradeability is maximized. The second driver point of contact with I-Shift is a stalk mounted on the steering column that controls the engine brake, and to a certain extent, the transmission. This stalk has three functions: in the ‘B’ position, it controls the engine brake application (40%, 75%, and 100%), and it will allow you to up- or down-shift to optimize brake output on steeper grades. In the ‘A’ position it manages brake output automatically, depending on sensed demand. Or you can select “Idle-drive” mode. This is very cool. When operating in slow-moving traffic, the engine will stay at idle speed, but you can toggle up or down through the gears depending on how fast traffic is moving. The engine adjusts torque output to suit demand so your fuel consumption is kept to a minimum while the drive is as smooth as it could be. The Smartware The electronics on Volvo engines and I-Shift are highly integrated; and combined, they’re equipped with a host of sensors that continuously calculate the vehicle’s speed, acceleration, torque demand, weight, rolling and air resistance, and road grade. This allows the engine and transmission to calculate and select the optimal power output and gear selection for any driving condition. This combination of built-in intelligence and data collection helps the transmission determine the appropriate starting gear and when it can successfully skip-shift. It can even sense when not to shift, such as when climbing a grade. I-Shift also responds to how you apply the throttle. If you go easy on the pedal, it will shift at low rpm, but if you’re hard onto the throttle, it’ll take the revs higher for more assertive shifts. It will skip shift if you’re gentle on the pedal but push it all the way down. On the other hand, if you’re easy on the pedal, it’ll shift a lower rpm, but take only one gear at a time. In addition, while you’re applying throttle, the transmission is sensing engine load as well as — get this — the grade the truck is on. This enables the transmission to determine if the shift will have to be quick with the aid of a bit of engine brake as might be the case shifting on an uphill grade, or it might look for an opportunity to skip-shift if you’re rolling down hill, you’re lightly loaded, or not working the engine too hard. It’s a clever bugger. The shift points are not hardwired. The engine and transmission sense what’s going on outside, and respond accordingly. I-Shift also features something Volvo calls a ‘Kick-down’ switch. There’s a distinct detent near the bottom of the throttle pedal travel range where you would normally bottom out the throttle. But if you push past that, the transmission will drop a gear and give you high rpm acceleration — much like flooring the throttle pedal in a car with an automatic transmission — which is quite useful for passing. Even operating in the automatic mode, the driver can initiate a manual shift by squeezing the shift trigger. In manual mode, arrows on the dash display alert the driver to the available gears, up or down, allowing up to three gears on an upshift if the conditions are favorable — like downhill, lightly loaded with a good tailwind. Among the more interesting features of I-Shift is a mode called “Eco-Roll”, where the transmission disengages the high-low splitter allowing the truck to coast down modest grades that do not require brake or power — with the engine at idle. Volvo says Eco-Roll eliminates parasitic drag of about 30 hp by letting the truck roll without any engine compression holding it back (kind of like Georgia-overdrive, but with safeguards) making more efficient use of vehicle momentum. Eco-Roll re-engages the engine as soon as one of the following happens: • The speed reaches the engine brake set speed for the cruise control; • The driver touches the brake; • The driver touches the engine brake control stalk; • The driver touches the accelerator; or • The vehicle speed increases past a pre-set cruise limit. Driving I-Shift Volvo has done a tremendous job making this transmission/engine combination think and perform very much like a driver naturally responds to many driving situations. It’s baseline programming tells it to configure for optimum fuel economy, and when you drive it gently, it shifts at low rpm (sensing minimal power demand). If you drive it aggressively, it will shift at higher rpm providing better performance. During the main part of Volvo’s presentation at the track in Savannah, we did laps while a tech guy in the passenger seat described the features of I-Shift. It went through the gears flawlessly, responding to throttle pedal input and shifting accordingly. When I put my foot into it, I was getting 1,800 rpm or better out of each gear and moving ahead rather assertively. It even fired the engine brake to facilitate a quicker shift. Alternately, when I feathered the pedal, easing it forward, I-Shift was leisurely shifting away at the 1,250-1,400 rpm point. Sensing no urgent need to accelerate, it chose not to bother with the engine brake. When slowing down in ‘E’ mode — non-aggressively as when exiting a freeway — I-Shift didn’t downshift every gear. It let me coast down to speed. If, before coming to a complete stop, I applied throttle, it shifted right into the appropriate gear in no less time than it took me to ease my foot down onto the throttle — and it chose a gear that matched the low-end of the rpm band for that gear, meaning I now had a full gear to go through before shifting again. I tried hard to fool the transmission by accelerating and breaking and accelerating alternately, in easy and aggressive style, and the darn thing found the right gear every time (and the right rpm range to match the way I was applying throttle), no hunting and pecking for a gear. It knew which gear it wanted and went right there. After the other journalists had boarded the bus and headed off to the airport, Steve Sturgess (of roadSTAR and Heavy Duty Trucking fame) and I piled into a truck for a little bit of real-world driving out on the freeway. I-Shift’s first test came in climbing the on-ramp for the Talmadge Memorial Bridge. From a dead stop at the bottom of the steep curved ramp (10% I’d estimate), we climbed up through the gears, the road grade sensor and the engine load calculator determining correctly that we were in a hard pull and needed speed PDQ. It took each shift up into the 1,800 rpm range, fired the engine brake and got right back into gear. I seriously doubt I could have managed that climb as well as I-Shift. As we topped the span and the grade began to level out, the shifting pattern changed; it made the shift at a lower rpm and let the revs fall unassisted by the engine brake. Out on the freeway, I-Shift did its thing in a less obvious way, just up and down shifting with road speed changes. I got a taste of the Eco-Roll feature several times as we rolled over various Interstate overpasses. As soon as the engine sensed the downgrade at the far end of the overpass, it kicked out of gear, the engine rpm dropped to idle (700-ish), and we rolled for quite a way before the transmission shifted back into gear and brought the revs up to match roadspeed. The whole exercise was so smooth, if I hadn’t been watching the tach, I might never have known it was happening. A couple of times during the drive, I made some pretty stiff brake applications, and unlike I-Shift’s lazy deceleration style described earlier, it sensed a more urgent need to slow and engaged the engine brake to help out while dropping a gear automatically to optimize output. I should mention here that Volvo’s new turbocharger design (a Holset electronically controlled variable-geometry affair) has greatly enhanced engine brake performance. We turned around at a truckstop about 40 miles south of Savannah, but not before going through the exercise of backing into a parking spot. Here’s where the clutch actuation really shone. Where a driver might ride the clutch while backing to control speed, the throttle pedal position signaled the clutch to tighten the engagement or back off, just as your left leg used to do. It went back just as smooth as could be at the speed I wanted to go and I really couldn’t sense the clutch engagement. It was as smooth as I’ve ever done it manually. That’s a real plus.