Hitting the sweet spot
The I-Shift Dual Clutch, available in Volvo’s FH13 model, offers a variety of performance benefits
I’M NOT REALLY SURE what I was expecting when I climbed behind the wheel of a Volvo FH 540 in Sweden recently. The Europeanmarket-only 6x4 rigid tipper and tri-axle pig trailer seemed pretty run of the mill for this part of the world as I walked towards it under a grey March sky.
But it was the writing on the door I was interested in; it loudly proclaimed that this particular truck was equipped with Volvo’s I-Shift Dual Clutch transmission. That all sounds well and good in theory, but what does that mean from behind the wheel?
I was about to find out.
There was nothing inside to give the game away in regards to the cog-box under the cab and the gear selector was still the familiar seat-mounted unit I was used to. So with the 13-litre engine chuckling quietly to itself I selected ‘A’ for auto and gently fed some juice into the drivetrain with my right foot.
The result once underway was quite startling; as the revs climbed the transmission power-shifted into another gear instantaneously, without any break in torque or power.
I must have had a rather stunned look on my face as my passenger, Andy Low, who also happens to be the Volvo Product Manager for Volvo Trucks International, grinned at me from across the cab. He’d clearly seen this reaction a few times previously. “Pretty surprising eh?”
The lag-free instant gear changing gives the 13-litre a real shot in the arm in terms of performance. Even though the revs rise and fall with each new ratio, the seamless unfurling of engine torque almost feels like a vehicle equipped with a CVT.
As I negotiated the Gothenburg test track the I-Shift transmission jumped from gear to gear and even into I-Roll with startling precision.
At a gross weight of 54 tonnes the FH was tackling our route seemingly without raising a sweat.
Clearly roles where trucks are tackling undulating country and start-stop conditions are where the dual-clutch will shine. However, the dual-clutch transmission also rewards in highway applications as the gear ratios are the same as the overdrive transmission currently found in the FH16.
Not only does this mean an unbroken continuum of power to the drive wheels when tackling big climbs and heavy traffic, it also provides lower rpm at highway cruising speeds, which means the engine is cruising in its fuelefficient sweet spot.
You’ve got to love an innovation that gives you both fuel efficiency and performance.
So what is Dual-Clutch I-Shift? To break it down into simplistic terms: it is often described as two transmissions and two clutches in the one package.
The gearbox itself has 12 gears; these are divided evenly onto two shafts – a clutch for each shaft. Once a gear is selected, the transmission, which takes its instructions from the gearbox control unit, effectively preselects the next gear on the opposing shaft. That gear is already spinning at the synchronised speed before the next clutch transfers engine torque to its own gear shaft.
The result is an unbroken stream of torque to the drive wheels that makes you question the horsepower badge on the side of the truck.
The only spot where there’s a noticeable pause is when the transmission moves from low to high range or when the transmission skip shifts.
It’s also worth mentioning that the I-Shift functions that we are already familiar with, such as Power mode and Manual mode, are still available on the Dual-Clutch I-Shift. As I found during my first drive at the Gothenburg track, the Dual-Clutch gearbox also still features the free-wheeling I-Roll function.
The speed at which the gearbox operates also does a good job of maintaining vehicle momentum without using engine power to regain any loss in road speed. So there are fuel gains to be had here too.
While that first test drive may have been on the other side of the world, Dual-Clutch I-Shift is now available in Australia in the FH13. It also has a GCM rating of up to 70,000kg which makes it a pretty attractive option for many B-double roles. Lighter GCM ratings can also mean a taller diff ratio to further capitalise on fuel savings.
No doubt we’ll be seeing a few stunned faces like mine was Down Under as people climb behind the wheel for the first time.
As always, feel free to send any questions you may have to [email protected]
“The result is an unbroken stream of torque to the drive wheels.”
MATT WOOD is a former truck driver, 4x4 and commercial vehicle journalist and writer. He now works for Volvo Trucks Australia in the role of Fuel Efficiency Manager, which encompasses traditional and alternate transport fuel solutions as well as telematics. He has a geeky interest in all things mechanical and an unrequited love for old Land Rovers.