VW Group subsidiary Scania has further distanced itself from exhaust gas recirculation as a means of controlling diesel emissions with the launch of new ratings for its modular engine family. The new engines were unveiled as the Swedish manufacturer launched the latest phase of its new generation trucks: the lower-entry G-series cab for distribution and inter-urban applications.
Sharing the style of the R and S cabs launched last year, the G-series has a lower seating position with three-step cab entry, making it more suitable for multi-drop work. Initially available as a sleeper-cab only, the new generation G-series will be offered with high, standard or low cab roofs. There’s 10 cm more headroom than the previous model in the standard cab, and 16 cm more in the Highline (high-roof) version. Like its larger counterparts, the driver is seated slightly further forwards than before.
Increased headroom has yielded extra space for overhead storage lockers front and rear on standard and Highline cabs, and the door bins are now wide enough to accommodate a 1.5-litre drink bottle. The sunroof has been enlarged and can now be operated electrically or manually. Underbunk storage can include a fridge, if required.
Acknowledging the increasing use of tablet computers in fleet management, the cab has a rotating holder that can be used to mount such a device on the instrument panel. The instrument panel can also be extended to allow the fitment of extra switches for auxiliary equipment.
Scania is also offering an optional cab Night Lock: a mechanical bar which makes forcing entry into the cab when the driver is resting inside extremely difficult.
Scania has deleted the exhaust gas recirculation (EGR) system from all its V8 engines, except the top-rated 730-hp variant. Better thermal and combustion control combined with an improved fuel-injection system means that NOx emissions can now be adequately controlled by Selective Catalytic Reduction (SCR) only.
There’s also a new power-rating for the V8, with a 650 hp/330 Nm engine being offered alongside the 520, 580 and 730 hp versions. Removing the EGR saves weight and fuel, and reduces the complexity of the engine and its cooling system at the expense of sometimes higher AdBlue consumption.
Moving down the power range, there’s a new, lower-powered, version of the keystone 13-litre straight-six engine. The DC13 370 joins 410, 450 and 500 hp stablemates: and all these engines now feature SCR-only emissions control, and simple fixed-geometry turbos along with new engine management systems and revised cylinder-heads. The DC13 also has a Miller camshaft (see below).
Scania’s nine-litre five-cylinder range has also been expanded and revised. Available at four ratings: 280, 320 and 360 hp; the engines have new management software and upgraded combustion chambers. The oil cooling system now incorporates thermostatic control, reducing fuel consumption by one per cent, and the new, larger, cooling fan is driven directly from the crank to reduce parasitic losses.
Compression ratio is up one atmosphere to 19:1. EGR is not used on the nine-litres, enabling the specification of a simple fixed-geometry turbo. The particulate filter on the 280 hp engine will not need active regeneration in normal use, Scania claims, making it ideal for urban applications.
Engines rated at 320 and 360 hp can be specified to run on pure biodiesel, such as rapeseed methyl ester, or any blend of this and mineral diesel. Biodiesel-specific engines will require more maintenance than their conventional counterparts irrespective of the fuel blend used: Scania said.
All standard Scania engines can be run on hydrotreated vegetable oil. Scania said that offering operators biodiesel-capable engines enabled operators to future-proof their fleets for the arrival of these fuels on the commercial market while using conventional diesel in the meantime.
A problem with running a large engine with a relatively low output, such as the DC13 370, is maintaining sufficient heat in the exhaust stream to enable emissions control systems such as catalysts and filters to function correctly. One solution is to burn extra fuel, either through post-combustion injection events or by injecting fuel into a burner downstream of the engine, but this is obviously wasteful.
Scania’s solution, developed initially by MSC students Clive Lewis and Henrik Dembinski using a single-cylinder Scania prototyping engine back in 2008, involves using a so-called Miller camshaft profile which delays closing the engine’s inlet valves until the piston is well on its compression stroke. This reduces the volume of air flowing through the engine, and therefore increases the exhaust gas temperature when the engine is running on part-loads without burning any extra fuel.
At higher engine loads, increased turbo pressure restores the amount of air flowing through the engine to a normal level.
Other means of achieving the same goal include variable valve timing and a throttled air intake: both of which are more complex than the Miller solution of installing a camshaft with a revised profile.
The Miller camshaft is named after American Ralph Miller, who patented the idea in the 1950s. Scania is understood to be the first truck manufacturer to use a Miller-profile cam, but the concept has been used in other applications including large marine diesels, diesel locomotives and, more recently, in the petrol engines of cars built by Mazda and Subaru.