The launch of a completely new heavy-commercial-vehicle V8 diesel engine is a rare event. In September, Scania, a subsidiary of the Volkswagen Group, will launch a new 16.4-L V8 engine, in addition to the Swedish company's existing 15.6-L V8, at the top of its heavy-truck range.
The engine uses Scania’s XPI high-pressure common-rail system to deliver fuel at a maximum injection pressure of 2400 bar (34.8 ksi), a departure from the PDE-type electronic unit injectors used for the 15.6-L V8 variants. Generally, the system operates at a typical injection pressure of 1800 bar (26.1 ksi), delivering two injection pulses: pilot and main to meet Euro-V and EEV emissions limits. The engine has been designed for compliance with Euro-VI and beyond, capable of delivering up to five injection pulses in each injection sequence. To deliver these pressures, the high-pressure fuel pump gains a third cylinder, compared with Scania’s inline engines.
A single variable-geometry turbocharger is fitted to the engine and features electric actuation to provide improved boost at low engine speeds. Cylinder heads are equipped with jet cooling to permit higher combustion temperatures. Drilled and machined holes in the base of the cylinder heads permit air to circulate around the casting.
Compared with the 15.6-L engine, the crankshaft bearing diameter is larger. A cylinder “saver” ring has also been introduced, designed to clean carbon deposits from the piston crown and help to reduce wear in the cylinder liner.
The result is an engine that produces 720 bhp (537 kW) at 1900 rpm and 2581 lb·ft (3500 N·m) between 1000 and 1350 rpm. Designated R 730 when fitted to Scania's heavy-truck range, the engine will be the most powerful available in a European series-production truck.
Exhaust emissions are controlled with selective catalytic reduction (SCR), already in use on the smaller V8. Compared with that engine, the 16.4-L engine gains a new SCR control system, integrated into the engine management system. NOx data is gathered from two NOx sensors. In addition to the single sensor downstream of the catalytic converter, a second sensor has been fitted upstream of the catalyst and immediately downstream of the new urea dosage point in the exhaust system. Scania claims that this can reduce AdBlue diesel exhaust fluid (DEF) dosing.
Power from the engine is transmitted using a revised version of Scania’s Opticruise automated transmission. The system is available either with or without a clutch pedal—used only for maneuvering when fitted. The transmission includes a single dry plate clutch with a higher clamp force than for the 15.6-L engine. Clutch activation is delivered by an electrohydraulic system with a maneuvering mode for the fully automated version.
The heart of the transmission is Scania’s range-change and splitter overdrive gearbox providing 12-forward speeds and two crawler gears. The gear wheels have been treated with double shot-peening and revised gear geometry. Maximum torque is only available in the top three ratios; otherwise, output is automatically reduced by 5 to 6% in the lower ratios.
Hill-holder is a standard feature of the fully automated transmission. The system works facing up and downhill. The brakes are held for around 3 s while moving the foot from brake to accelerator pedal and will not release until drive torque is enough to prevent rollback. Drive options include single and hub reduction axles.
The new engine shares the 154-mm (6.1-in) stroke with the 15.6-L engine, but the greater capacity is produced by increasing the bore from 127 to 130 mm (5.0 to 5.1 in), identical to that for the company’s 9.3- and 12.7-L inline engines.
To handle higher combustion pressures while controlling weight, compacted graphite iron (CGI) is used for the new cylinder block construction. The engine adopts other familiar Scania features such as individual cylinder heads.