Volvo dual clutch technology has been available for some time in Europe, but has finally made its way here, after prolonged testing in Australian conditions.
There are now examples of the new gearbox option on the road and Diesel News took the opportunity to drive a B-double out of Brisbane, up the Toowoomba Range and along to Cunningham Gap, before returning down from the Dividing Range to Brisbane.
There have been dual clutch vehicles in Australia before. They are an option in Volkswagen cars and available as the Duonic option on the Fuso Canter model. Volvo’s introduction of the concept is a first for the heavy end of the market.
The first thing to say about the driving experience in a B-double using this dual clutch I-Shift is this truck is very much a known quantity. Even without a dual clutch this is a very smooth and swift gearbox and the interruption in power out on the highway is almost imperceptible as it is.
We have become used to the smooth ride and low engine noise in the cab as we relax into driving the Volvo FH. This is the truck’s natural environment and it is clearly relaxed and moving with easy.
On the flat open highway out towards the Lockyer Valley, it takes a lot of concentration to try and hear the gear changes when they occur. In a normal I-Shift, the driver can hear the changes if they listen out for them. On this truck the only way to work out when a change is made is to keep a keen eye on the tachometer and watch it step down in revs to the next gear.
One of the reasons behind introducing the dual clutch is to improve the performance of 13-litre powered FH prime movers. Trucks buyers can be offered a normal direct drive top gear I-Shift behind a 13-litre in an FH prime mover with a 3.09:1 rear axle ratio, if fuel is a priority. However, introducing the dual clutch enables the FH to be offered with a 3.4:1 final drive ratio as the dual clutch utilises the overdrive version of the I-Shift gearbox.
On the road this configuration plays out as 1375rpm on the clock as we head out towards the range at 100km/h. When the truck starts to get into this kind of rpm territory some real fuel savings are likely to be the result. Getting these figures right with a normal axle ratio and overdrive box helps to retain gradeability and startability while driving fuel consumption lower.
This new configuration may enable Volvo buyers to choose the lighter and cheaper 13-litre option over the 16-litre for general day-to-day line haul where the truck isn’t at top weights all of the time, as the performance of this set up comes close to meeting the requirements for these kinds of tasks. Truck buyers can opt for the dual clutch in any FH or FM with the 13-litre engine fitted, but, even Volvo will admit, it is not the right solution for everyone.
Volvo are happy to quote claims of a three per cent improvement in fuel economy over the 13-litre with a normal I-shift. It would seem there are applications where this combination of gearbox and engine would out perform the standard gearbox with a 13-litre, in terms of fuel use, and come in at a lower tare than the 16-litre version while still being able to perform reasonably well.
In terms of the feel of this new gearbox option, the point at which it is obvious this is a different transmission is when the B-double starts to hook into the bottom slopes of the Toowoomba Range.
While anyone familiar with automated manual transmission (AMT) will be used the momentary pause as the computer activates the clutch, selects the new gear and re-engages the driveline, the sensation using the dual clutch is very different. There is no pause, no momentary feeling of the truck slowing. This is genuine power-shifting and there is zero loss of momentum.
Of course, logically there must be a point where one of the clutches has to disengage before the other clutch engages, but we are talking about a computer controlled system here and the time lapse must be a nano-second. From the driver’s seat there is no sensation of any interruption in power. The truck just powers on through every gear change, without a blink of the eye.
This is where the point Volvo make about loads like liquids, which can react quite strongly to even a small interruption in power, comes home to the driver. Climbing an incline like this is made harder when the freight starts to slosh back and forth in time with gear changes in a manual gearbox. With this set up the problem disappears. The dual clutch would be ideal for a 19m B-double tanker.
The other issue in which this transmission may help is if there is a risk of losing traction. The fact that the power is continuous means there is no break in power transmission and a lower risk of slippage.