8 minute read
SUPER DRIVELINE FROM SCANIA
ON THE ROAD I had a brief back-to-back drive in a current R450 and a new 460R Super (the power rating now proceeds the model designation) on a recent trip to Scania's home town of Södertälje, Sweden.
I would like to say that I immediately noticed the additional 10hp, but didn't. What was obvious however was how the new 13-litre is more refined, and quieter too. It's also happier to lug at lower revs, with maximum torque now being available between 900rpm and 1,300rpm. Obviously lugging at lower revs means fewer gear changes, which correlates directly with improved fuel economy.
The 460 is matched to the new G25 transmission. Gear changes are quick and flawless, and there was certainly no temptation to override it on my short drive. I was particularly impressed with how smoothly it re-engaged a gear after a spell in Eco-roll. For the bulk of my mainly motorway journey, the truck was either in 12th gear, overdrive or Eco-roll.
My test truck was fitted with the new CRB and a retarder, the two working effortlessly together. There are four settings, the first being the traditional exhaust brake, followed by CRB, then the retarder, and finally CRB together with the retarder.
The old R450 was unquestionably already an excellent driver's truck, but it's just been usurped by the 460R. What's more, with a claimed improvement in fuel economy and a payback in just 18 months, it's also likely to improve Scania's operator appeal too. of electric vehicles, customers are not buying to the extent needed to make a big difference,” explains Traton Group CEO and Scania CEO and President, Christian Levin, when I ask him how he can justify investing in a new family of combustion engines.
“So the most efficient thing we can do is work on 99 per cent of the sales, and improve the combustion engine. If we can take out 10 per cent fuel, that is 10 per cent less CO2.
But Levin confirmed that this is indeed the ‘final hurrah’ for the diesel engine, and said Traton Group’s R&D budgets are quickly shifting away from combustion engines, and into autonomous and electrified transport.
SO WHAT EXACTLY IS THE SUPER DRIVELINE? At the heart of it is a new DC13 12.74litre, 6-cylinder engine is, which according to Scania, is the most
advanced engine platform in the industry today. It’s also claimed to be the most efficient too, operating at a class-leading 50 per cent thermal efficiency. This, says Scania, makes it 5.2 per cent more frugal than the ‘benchmark’ 13-litre engine it replaces.
The single cylinder head, dual overhead camshaft engine, has allowed Scania’s engineers to raise the peak pressure inside the cylinders to 250 bar. This, together with the refined injectors, secures a more thorough combustion of the diesel. The downside to this more efficient burn, is a higher level of raw NOx, which is tackled with the same Twin SCR system that was first launched on its new V8s last year.
The first dose of AdBlue is injected in the close-coupled position to the turbo charger, immediately after the exhaust brake flap where the exhaust gases are still very hot. The second dose is then injected in the usual position inside the after-treatment system. By then the task is easier since the peak NOx level has already been reduced. The particulate filter, which is positioned between the two SCR catalysts, is regenerated without post-injecting
extra fuel to the exhaust system.
“We believe that the new aftertreatment system with the Scania Twin SCR solution is of great interest for our industry,” says Magnus Henrikson, Scania’s Chief Engineer. “It brings increased efficiency to Scania’s internal combustion engines and ensures that they are compliant with, or even exceed, current and expected emission legislations around the world, for the foreseeable future.”
Double dosing has led to an increase in AdBlue consumption from eight per cent to 12 per cent.
The engine is offered in power ratings of 420hp (2,300Nm), 460hp (2,500Nm), 500hp (2,650Nm) and 560hp (2,800Nm). All versions can run on hydro-treated vegetable oil (HVO), and the two middle rated ones can be adapted to run on 100 per cent renewable biodiesel.
The DC13 is matched to a pair of automated manual gearboxes, the G33CM (which was launched last year on the new V8s) or its brand new smaller sibling the G25CM. The difference between the two is physical size, the G25’s all-aluminium housing being slightly smaller.
Respectively they have a 60kg and 75kg weight advantage over the gearboxes they replace. The lighter of the two can handle torque levels of up to 2,500Nm, making it ideal for the 420hp and 460hp engines.
Both gearboxes have 14 forward gears (including a super crawler and an overdrive), and up to eight reverse gears.
Another major component in the new driveline, and one that is crucial in allowing Super trucks to cruise at 900rpm, is the new R756 rear axle. Developed jointly between Scania and its Traton sibling MAN, the new multipurpose axle will eventually be available with eight different gearings, the fastest being 1.95:1.
Scania says the axle, which has an oil drain interval of 750,000km, contributes one per cent of the Super driveline’s fuel economy saving.
In addition to the traditional exhaust brake, Super trucks are offered with the optional Compression Release Brake (CRB) auxiliary braking system. Operating on all 6 cylinders, the system provides 350kW (1,500Nm) of braking performance, which Scania says will allow some operators to specify it over a retarder. It weighs just 7kg, as opposed to 100kg for the R4700D retarder.
DIGITAL MIRRORS Hot on the heels of Mercedes-Benz, DAF and MAN, Scania is the latest truck maker to replace conventional mirrors with a camera and screen system. The Scania Mirror View Camera system (SMVC), which is a retrofit option in Europe, consists of cameras mounted on the outside of the truck, which feed images onto a pair of 31cm tall screens fitted to the A-pillars.
Unlike the DAF and Mercedes systems, which have cameras mounted high up on the sides of the cabs, SMVC's cameras are located on the doors. In my opinion they look more aesthetically pleasing in this position, and are integrated into the truck's styling lines. They also provide a better view of the prime mover's rear wheels than some systems Iove tried, which will presumably make reversing onto trailers easier.
The two A-pillar-mounted screens offer superb clarity, and it even coped admirably with the low winter sun. But annoyingly the field of vision on the main screen is rather narrow, and you soon lose the rear of the trailer. Rival systems follow the trailer's tail while cornering. The wide angle section is better, but very small, and consequently more difficult to see. Unlike the DAF and Mercedes systems, there aren't any lines on the screen to depict the rear of the trailer or to show when it's safe to pull in after an overtaking manoeuvre.
CRB is claimed to work at up to 65 tonnes in flat operations and 40 tonnes in slightly hilly conditions.
Increasing urea consumption from eight per cent to 12 per cent means having to carry significantly more AdBlue, which posed a problem for Scania’s engineers. As there is only a finite amount of space on the chassis, it would have to reduce the diesel tank dimensions. The question was, how could it do this without affecting the Super’s range?
The answer they came up with is a Fuel Optimisation Unit (FOU). In the black box, which is attached to the front of the fuel tank is a small 26-litre catch tank. From here, an electrical feed pump pushes the fuel to the engine, first cleaning it of dirt and water. This allows the truck to use 97 per cent of the diesel in the main tank, whereas normally only 87 per cent is accessible.
“Diesel engine fuel injection systems must not be allowed to suck in air, which is a risk when you have a long fuel tank and drive uphill or downhill, so that the fuel stays in one end of the tank for a while,” explains Ola Brantefors, head of chassis layout and installation. “Our fuel optimisation unit works as a catch tank that mitigates the problem by holding a sufficient volume of fuel for feeding the highpressure system on the new engine. This means that we have been able to increase the usable amount of fuel in our tanks, since we no longer need to keep a ‘reserve’ level to avoid sucking in air.”
Scania gave the example of a typical 4x2 prime mover, which would previously have been equipped with a 105-litre AdBlue tank, and twin diesel tanks of 500 and 700 litres. It said an equivalent Super would have a 123-litre AdBlue tank, and both a 420-litre (with FOU) and 615-litre diesel tank.
Despite carrying 165 litres less diesel, FOU would ensure that the useable volume was only 49 litres less than before. Then by the time the 8 per cent fuel economy improvement is taken into account, the Super’s range would be 136km greater than the older tractor.
