Dual-shaft transmission has already secured its place in the automotive world in applications ranging from racing cars to touring motorcycles. The DSG (direkt schalt getriebe in the original German, which translates to direct shift gearbox) was first developed by Porsche for its endurance racing cars in the 1980s. However, it gained popularity when it was developed into a production system by Borg Warner and then initially licensed to the Volkswagen Group, which rapidly incorporated it across its whole product range including light commercial vehicles.
DSG technology
The DSG’s construction incorporates two separate gear trains, arranged in parallel. One provides the gears for the odd numbered gears, and the other for the even gears. A wet clutch pack has two concentric plates that transmit drive to one or other of the gear sets as directed by the controlling computer.
The electronics are smart enough to guess that if you are in second gear and accelerating, the next gear you will need is third, so it pre-selects it. When either the driver, in manual mode, or the computer, in automatic mode, decides that it’s time for third, the clutch plates are hydraulically moved along their shaft to swap drive from one to another. The whole process takes just a few milliseconds, much faster than even the best driver could match with a conventional gearbox.
I-Shift Dual Clutch transmission
Volvo has become the first company to use it on a heavy-duty truck, where it is known as the I-Shift Dual Clutch (DC). The DC shares the same software as the conventional I-Shift so the same shift strategy is used. The gearbox is just as happy to make block shifts as normal, and these, even on the same shaft, are virtually as fast as single shifts. In normal circumstances, the transmission will take the alternate ratios up to 8th, then singles. The only exception to the ultra-fast shifting is due to the range change mechanism being the same as in a conventional transmission, so the shift from 6th to 7th, and back, is at a similarly conventional speed.
All this technology comes at a cost, both financial to the tune of £5,000, and in terms of weight with an increase of 101kg over a normal I-Shift. It is currently available on Volvo’s 13-litre FH range with ratings of 460hp, 500hp and 540hp, and at weights up to 60 tonnes GCW.
The other major novelty on our review FH 500 DC is the unique paint, which isn’t, as most observers think, a vinyl wrap. Volvo’s development people were looking for a guinea pig vehicle for a new paint process just as the FH was being ordered. The 6x2 was ordered with no final paint coat and at the end of the line, it was taken to the special vehicle preparation facility where the matt black paint was applied. It was considered a success and is now an official option in a range of colours and at the same cost as a regular metallic finish. Some orders have been received from UK operators. It certainly looks distinctive but isn’t the easiest finish to keep clean. As a final touch, the new set of alloy wheels was sand-blasted and painted to match.
Cab interior
This review truck's FH Globetrotter XL cab was fitted with the Living 1 layout with single bunk and 440mm-high rear lockers. The alternative Living 2 has two bunks but its lockers are only 200mm deep. Volvo provides cab equipment in pre-ordained packages. Our review FH 500 DC has the highest level available on a 13-litre model, the Driving ++ pack.
Seat comfort
Given that 99% of the time in the cab is spent either sitting at the wheel or relaxing, the facilities for these are vitally important. Both two-tone leather trimmed front perches feature whole seat reclining, while the passenger side has swivel and cushion fold-up functions as well. The driving seat comes with ventilation that provides cooling or warming air at the same temperature as the digital climate control.
Globetrotter XL living space
At break time, you can get your pie out of the 66-litre fridge beneath the bunk, warm it in the microwave that you hooked up to the prepared point in one of the rear lockers and eat it at the generously sized table that appears between the seats. Then at the end of the day, you have a choice. Sit on the swivelled passenger seat or on the bunk, which is just the right height, or if you feel decadent, lounge on the bunk with its electrically reclining top third section.
As the top of the dashboard is mostly flat, apart from the rubber birdbath-like tray, you can watch your entertainment on your laptop or tablet, or on a TV fitted to the ready prepared mounting above the door.
D13K engine design and emissions
Volvo’s D13K follows the proven architecture of the 13-litre engine family and moves it on to Euro-6. The long-stroke 6-cylinder block is topped by a single overhead camshaft operating four valves per cylinder. The timing mechanism, which as well as the camshaft drives pumps for power steering, oil, fuel and compressed air, is mounted at the rear of the block. This provides a compact arrangement as well as contributing to the considerable cooling requirements of all Euro-6 engines. The rear mounted timing mechanism makes it easy to add the 650Nm or 1,000Nm power take-off.
High-pressure electronic unit injectors provide the first stage of the Euro-6 combustion process, which continues through an uncooled exhaust gas recirculation system. The chemical after-treatment process consists of four devices, including the diesel particulate filter and the SCR unit where the AdBlue is injected, in this case at the rate of 7.5% of diesel consumption.
DC transmission performance
You don’t get far in the FH 500 DC before you realise that you’re driving something a little bit different. Even with normal I-Shift, which is as good as current automated manual transmissions get, there’s a measurable delay as up-shifts are made, particularly when moving away from rest. With the DC, the acceleration is almost linear, with the shifts virtually imperceptible without watching the rev counter.
At road speeds a bit further up the scale, the process feels slightly illogical as shifts are faster on a light throttle. It’s when the driver chooses to over-ride the automatic function that the true speed of the shift is apparent, as the slowest part of the process is the press of the button, followed by the electronics passing the decision to the clutch mechanism.
On tougher road sections, it takes a bit of self-discipline to make better progress by not flooring the pedal. Allensford Bank on the A68, the climb up to Castleside, is probably the toughest single piece of road on the CM truck review route, and more than one review has come to a wheel-spinning halt as the break in drive during a downshift has overcome the available grip, especially on a 6x2 if you don’t dump the third axle in advance. With DC, even on a damp and greasy surface, there was no need to lift the axle, with not a hint of wheelspin evident from our FH 500 review vehicle.
Beside the DC technology, the transmission features an overdrive top gear and a 2.85:1 rear axle ratio. In combination, these give a very relaxed drive in the FH, with 50mph in top pulling just 920rpm. Below 50mph, this was too low, so the electronics did as a decent driver might do and chose 11th most of the time on A-road running, putting the revs bang in the middle of the torque plateau at 1,200rpm.
Fuel consumption: Volvo FH 500 DC 6x2 mpg performance
The gearing may have contributed to the less-than brilliant fuel economy of 7.32mpg overall in our review, and more than the usual amount of red lights on the A5 didn’t help. Better fuel economy isn’t claimed as a DC benefit, but it’s not meant to be significantly worse, either. We’re still gathering fuel consumption data with the higher road speeds on the route, but it’s beginning to look as though 8mpg is a realistic target for a regular medium-powered 44-tonner.
[ADD Volvo FH 500 DC review Volvo branding 1.JPG]
Driver assistance systems
Being a state-of-the-art Volvo, you’d expect our review FH 500 DC to have the latest safety technology, and it didn’t disappoint. In fact, the only significant driving aid missing was the I-See predictive cruise control. We didn’t have any need to benefit from the advanced emergency braking, but the companion adaptive cruise control works so unobtrusively that it is easy to forget that you have it until you find yourself gradually slowing down behind traffic that you could have overtaken.
The nearside collision avoidance system, or Lane Change Support as Volvo says, is a bit disconcerting the first time you experience it. The warning if you signal left with an object in your blind spot sounds like a normal car horn, which leaves you looking around to see who you’ve upset.
We encountered another first during our review when the Volvo FH's information display flashed a warning from the ABS that the road was slippery, and the driver alert support at one point suggested that a break would be in order. The first two axles on our review vehicle were fitted with wide and low tyres, Michelin XFA2s at 385/55, which Volvo says provide better rolling resistance. We can’t judge that but we can confirm that there was no noticeable problem with front-end grip even on the greasy bits.
Also new on the review FH 500 DC 6x2 was Volvo’s dynamic steering. Our verdict is that, although great for hamsters and at low speed, it is too light and over-sensitive at higher speeds, and it doesn’t work at all when the parking brake is on.
Review verdict: 80%
We make no apologies for concentrating heavily on the transmission in this review. That the FH is a thoroughly competent product is a well-established fact as proved by our previous reviews and by its success in the marketplace.
The Volvo Dual Clutch gearbox lives up to its promise. It changes gears smoothly, speedily and effectively without any interruption in traction. In that respect, it’s at least a match for the traditional epicyclic automatic gearbox that dates back more than half a century. It is also significantly cheaper and doesn’t suffer from the slippage of a torque converter. So that leaves the question of who it is for.
We’ve already seen one prominent haulier specify it, but that was for his personal £750,000 horsebox, so doesn’t really count as an informed business decision. But there are other animal transporters, both those standing on their feet and hanging from the roof, which would benefit from a smoother rate of progress. Likewise, bulk liquid hauliers could see a benefit. Probably the biggest beneficiaries, though, are operators working in extreme conditions such as forestry, where spinning to a halt could be a bad thing.
It’s these advantages that will make it an even better proposition in the FM and FMX ranges than in the FH, as these are more likely to be used in difficult conditions, and Volvo will start taking orders for these models soon.
Our prediction, after reviewing this FH 500 DC 6x2, is that as availability increases and production follows demand, with the economies of scale bringing the price down, DSG is in heavy trucks to stay, although it will never totally replace current products with their lighter weight.
Images: Tom Cunningham