Evolving the 16.4L DC16 V-8 to meet stringent emissions standards
AS EMISSIONS standards become more stringent every year, engine manufacturers continue refining their products in an effort to keep them viable.
In the modern-diesel space, simply adding more emissions equipment to an engine to comply with standards is a temporary fix at best. In order to truly meet emissions requirements head on, a new powerplant or an updated version of an existing engine must be designed from the inside out. Scania understands this, and the company has taken its established workhorse, the DC16 diesel V-8, and made it lighter, more efficient, and cleaner.
For years, Scania’s DC16 has been a go-to engine for everything from over-the-road trucks to ore haulers. The family of DC16 engines currently has four members, making 520 hp (1,991 lb-ft of torque), 580 hp (2,212 lb-ft of torque), 650 hp (2,433 lb-ft of torque), and 730 hp (2,581 lb-ft of torque). Three of the engines (520, 580, and 650) have an all-new, 176-pound-lighter layout that only borrows the
block and configuration from the previous generation, while the 730 (due to its higher output) retains the last-generation platform, updated to improve efficiency and emissions.
One of the more dramatic changes occurs in the turbocharging system on three of the engines (730 carries over a variable-geometry turbocharger). Gone is the single-scroll VGT that is fed by a single collector for both cylinder banks. In its place is new technology Scania calls a rotated twin-scroll fixed-geometry turbo. The twin scroll’s turbine is fed by two exhaust-gas collectors, one per cylinder bank. The exhaust gases are utilized more efficiently by the FGT, which is lighter and more robust than the ’charger it replaces. It is also mounted directly to the block in the valley to make it more stable, with a vibration-proof operating environment.
The DC16’s induction and injection processes are calibrated to work with the selective catalytic reduction aftertreatment. The intake is now straighter and provides more direct airflow into the engine. Fueling is managed by Scania’s XPI high-pressure pump that feeds diesel through a central pipe and long distribution lines to the injectors. For increased efficiency and reduced fuel consumption, the pump is comprised of only two pistons and has maximum cylinder pressure of 210 bar. The injection system uses a maximum pressure of 1,800 bar (down from 2,400 bar) to better complement the SCR technology.
Better efficiency also comes through reducing friction.
Scania reworked the DC16’s cylinder heads, pistons, piston bolts, crankcase, crankshaft, and bearings to provide better sealing and a reduction of friction. The modular heads (each cylinder has an individual head) are accurately machined and designed to withstand the thermal and mechanical stresses that occur during millions of combustion cycles.
Different technologies are used to further reduce the parasitic loss that increases fuel consumption on all four engines. The air compressor and coolant pump only engage when needed, helping reduce drag on the oil-burner. A pilot-controlled oil pump allows the pressure to be adapted to the engine’s needs, while a thermostat regulates and optimizes oil temperature and pressure. The fuel pump and compressor are also moved to the rear of the engine to simplify the belt-drive system.
Low-output, large-displacement engines produce too much air for the amount of heat developed, which can affect the SCR system. So a special camshaft that holds the intake valves open longer during the compression phase is used in the 520. By doing
this, the engine actually gets less air in the cylinder, which helps maintain a higher working temperature for a more efficient burn. The compression ratio on the 520 is also raised to 22.2:1. American engineer Ralph Miller developed this technology during the ’50s.
The emissions system (excluding the 730) consists of only SCR technology—there is no EGR. The SCR has an integrated exhaust silencer that is used to manage the aftertreatment. Internally, it consists of an oxidization catalyst, AdBlue mixer, two particle filters (short filters with asymmetrical walls for reduced back pressure), three parallel SCR catalysts, and three ammonia slip catalysts that scrub the exhaust. The whole unit is only 24 inches wide, which saves valuable space. The 730 uses the same
SCR, but it retains an EGR. All four engines meet EPA Tier 4 final and Euro
Stage VI emissions standards.
The newest generation of Scania’s DC16 uses a twin-scroll fixed-geometry turbocharger that is fed directly from the two exhaust collectors, one from each cylinder bank. The FGT is lighter and more robust than the single-scroll variable-geometry turbo it replaces. The intake is redesigned for more direct airflow into the cylinders. The high-pressure fuel pump and air compressor are moved to the rear of the engine.
Parasitic drag in the engine is reduced by a water pump and air compressor that disengage when not needed. The engine’s weight was cut 176 pounds by simplifying the layout with fewer parts.