New powertrains for construction vehicles
Scania is launching a range of powertrains for the new C-class construction vehicles at the Geneva truck show. New, modified and upgraded components in combination with the new C-class chassis produce highly specialised vehicles for conditions ranging from medium-heavy tipper duties to tough site and off-road operation with all-wheel-drive options.
New components include a 12-speed range-splitter gearbox, a light tandem bogie and an in-house-developed driven front axle, as well as the new 12-litre and thoroughly modified 14-litre engines already launched. Carry-over components from the 3-series have been upgraded and extensively revised.
(More details about specifications and component combinations are given in release P96133.)
Scania 12-litre engine – an ultra-modern high-efficiency six
Launched together with the 4-series in October 1995, Scania’s new 6-cylinder 12-litre engine produces 400 hp (DSC12 01). Torque delivery is high and flat, suitable for both construction work and long-haulage.
Simplicity and serviceability have been guiding principles for the design. Scania has therefore adopted a robust design with the camshaft placed high in the block and acting on short, sturdy pushrods. Separate cylinder heads with four-valve technology are used. The cylinder block features replaceable liners with a new type of lower attachment, which provides better cooling at the top of the liner, around the combustion chamber.
Articulated pistons are used, featuring a steel crown attached to the lower aluminium section by the gudgeon pin. The steel crown can withstand higher pressure and higher temperatures, and the piston rings can be positioned higher up to reduce the "dead volume" in the combustion chamber. This design improves fuel consumption and smoke emission. The pistons are gallery-cooled by oil sprayed into the pistons via nozzles at the bottom of each cylinder.
With the aid of four-valve technology and a new generation of EDC, the combustion process in the cylinder has been optimised to provide as efficient gas flow and combustion as possible. Scania’s 12-litre engine has a very high efficiency rating compared to most other production diesel engines for heavy trucks (189 g/kWh).
Scania 14-litre engine – outputs and efficiency improved
Scania’s legendary 14-litre V8, first launched in 1969, now features an advanced electronic fuel injection system, which benefits fuel consumption and emission control. The basic engine has been entirely revised and strengthened over the last couple of years.
With outputs of 460 (DSC14 15) or 530 hp (DSC14 13) and massive torque available over a wide rev range, these engines are designed for the top-horsepower segment. Such performance is ideal for various types of very heavy specialised haulage and long-haulage in countries with high permissible gross weights.
Separate cylinder heads are fitted and the cylinder block has replaceable liners. Articulated pistons are used on the top-output 530-hp engine, while all-aluminium are fitted to the 460-hp engine.
The injection system is based on a new generation of EDC (Electronic Diesel Control). Both the amount of fuel injected and injection timing is controlled by the system, permitting precise control of the combustion process under all load conditions. With improved power, torque and environmental performance, specific fuel consumption is 192 g/kWh for the 460-hp and 193 g/kWh for the 530-hp version.
One new and two familiar gearboxes
Scania's current gearbox generation was launched in 1991. On 4x2, 6x4 and 8x4 vehicles, the 400-hp 12-litre engine is combined either with the Scania GR900 or GRS900 gearboxes. GR900 is a range-change unit with 8 road gears and one crawler. The GRS900 is a range-splitter with 12 road gear and two crawlers. The 14-litre engine is fitted with the GRS900 at both output levels, 460 and 530 hp.
All-wheel-drive (4x4, 6x6) vehicles are all powered by the 12-litre engine in combination with the new 12-speed GRS890 range-splitter gearbox. The GRS890 is derived from the GRS900, but does not have its crawler gears. Crawler ratios are not needed on all-wheel-drive vehicles since they are equipped with a 2-speed transfer box, giving extra-low ratios.
Scania Retarder – now also for construction vehicles
The familiar Scania Retarder is available as an option on all gearboxes. Unveiled at the Brussels show in 1993, the hydrodynamic retarder is designed and produced inhouse by Scania. The retarder is integrated in the gearbox and has compact dimensions and low weight, compared to retrofit alternatives. Cooling is via the engine’s cooling system. The system interacts with other control systems on the vehicle, including EDC, exhaust brake, ABS and TC (traction control). A downhill speed control function allows a constant speed to be maintained automatically.
The retarder produces approximately 500 kW, and the exhaust brake on the 14-litre engine close to 200 kW, both figures at 2,000 r/min engine speed. Retarder output is automatically optimised in relation to the coolant temperature, which means that the retarder is most efficient at high road speed. The exhaust brake on the other hand is most efficient at low speed (below 40 km/h). The high output of the retarder means that the wheel brakes are normally only employed in 25% of brake applications.
The transfer box on all-wheel-drive vehicles is available in two strengths: GTD800 for 4x4 vehicles and 6x6 with 21-tonne bogie weight, and GTD900 for 6x6 with 26-tonne bogie. Both are 2-speed with a road ratio of 0.89:1 and an off-road ratio of 1.536:1.
The V-shaped chassis frame used on the 4-series permits the whole powertrain to be mounted lower in the chassis. Universal-joint angles are therefore improved compared to previous all-wheel-drive models, giving smooth and even power transmission with less strain and wind-up on both front and rear axles.
The driven front axle is a new in-house Scania design featuring hub reduction and generous ground clearance. It is designed for front axle weights up to 9000 kg and the gear ratios allow it to be combined with several other axle gears.
Two rear axles, three tandem bogies
Depending on application and weight, the rear axle or bogie is either of the single-reduction or hub-reduction type. All Scania rear axles have been up-rated in recent years to cope with the reverse torque involved in retarder braking.
4x2 models are fitted with either the single-reduction R780 or hub-reduction RP832 axle gears. 4x4 vehicles always have the RP832.
P124 and R124 models in 6x4 and 8x4 configuration are available with a new light tandem bogie intended mainly for on-road and light off-road operation. Replacing previous single-reduction tandem bogies, the suspension and mechanical layout is based on the light hub-reduction bogie launched in 1993 (see below). Sharing the benefits of light weight and simple design, these two bogies also have a number of components in common. The RB660+R660 axle gears used have a wide span of ratios, also for on-road cruising speeds.
A choice of two hub-reduction tandem bogies is available across the C-class range – i.e. including the R144. The lighter of the two, RBP730+RP730, has parabolic springs and plenty of axle articulation. Generous ground clearance, snatch-free power transmission and good axle control provide outstanding mobility. The sturdiest tandem bogie is fitted with RBP832+RP832 hub-reduction axle gears, permitting bogie weights of up to 30 tonnes.