Hit­ting the sweet spot

The I-Shift Dual Clutch, avail­able in Volvo’s FH13 model, of­fers a va­ri­ety of per­for­mance ben­e­fits

Owner Driver - - Fuel Talk - Matt Wood

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.

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