Mercedes-Benz reveals its plans and tech for an all-new generation of powerpants, including a potent new twin-turbo 4.0L V8, new in-line 4 and 6 cylinder engines and various clever new tech, starting with a new 48V electrical system and mild hybrid functions.
Mercedes is rolling out not one, but four brand new engines with eight, six and four cylinders, all equipped with clever tech and modular components across the engines, including a standard 500cc cylinder displacement, help to improve fuel economy and enhance performance.
M176 AMG developed new V8 for the S-Class
The new V8, codenamed M176, will be built in Untertürkheim and is dedicated to the Mercedes flagship model, the S-Class. It will be offered from mid-2017, replacing the current M278 V8 with 455 hp in the S 500. Official power output has not been announced, but Mercedes promises more than 476 hp and 700 Nm at 2.000 rpm.
The V8 will get advanced tech solutions such as the turbochargers mounted in between the cylinder banks (‘hot inner V’), a formation first seen on the Mercedes-AMG GT V8 (M178). This particular arrangement generates a 5% power gain compared to the old M278 V8. The engine is of closed-deck construction, which means that the engine block cover plate is extensively closed in the area around the cylinders. The engine block is of an aluminium alloy and produced by permanent mould casting. The cylinder head uses an aluminium-zirconium alloy, which is a better conductor of heat than the standard aluminium alloy.
The new V8 biturbo employs a centrifugal pendulum to reduce both the fourth-order vibrations in eight-cylinder mode as well as the second-order vibrations in four-cylinder mode. A combination of biturbocharging and direct petrol injection with spray-guided combustion increases the thermodynamic efficiency, thereby reducing the fuel consumption and exhaust emissions. Particularly fast and precise piezo injectors spray the fuel at high pressure into the eight combustion chambers. Multiple injection occurs on-demand, ensuring a homogeneous fuel/air mixture. The delivery of fuel is electronically controlled and fully variable for a fuel pressure between 100 and 200 bar.
Fuel economy is also paragon for the new engine. According to Mercedes, the new V8 consumes 10% less fuel thanks to its smaller displacement (3.982cc versus 4663cc) and clever cylinder deactivation system. Between 900-3250rpm (in Comfort or Economy driving modes only) cylinders 2, 3, 5 and 8 are shut off. The cylinders can be reactivated in milliseconds as soon as the acceleration is pressed on or as soon as the engine speed goes above 3250 rpm. CAMTRONIC valve timing reduces the pumping losses while improving the overall efficiency of the remaining four cylinders by shifting the operating point towards higher loads.
The cylinders are turned on and off by the interplay between engine control and actuators on the cylinder head. The switchover to four-cylinder operation is accomplished by eight actuators that act on the axially movable cam parts of the intake and exhaust camshafts via a selector. These cam parts are held on the carrier shaft by gears and are locked in the respective end positions by means of a locking mechanism. The intake and exhaust valves of cylinders 2, 3, 5 and 8 do not open due to the zero-lift cams of the cam parts. At the same time, the fuel supply and ignition are deactivated, so that no unburned mixture is left in the deactivated combustion chamber.
The M 176 has exhaust aftertreatment with two catalysts directly mounted on the engine and on the underfloor. The as-standard particulate filter is part of the exhaust system under the floor.
M256 six-cylinder inline gasoline with mild-hybrid tech
Another significant premiere is the new six-cylinder inline gasoline engine (codenamed M256), the first-ever Mercedes engine designed to support mild hybrid and electrification applications right from the outset. It will debut in 2017, again on the flagship S-Class, at first, but it will eventually filter down to the smaller E-Class.
The main innovation is the 48V electrical system. The Integrated Starter-Alternator (ISG) and electric auxiliary compressor (eZV) combine to produce a power boost that negates turbo lag, while the system also serves the classic roles of powering the water pump and air-conditioning compressor. The 48V ISG is also responsible for hybrid functions such as boost (up to 15 kW), energy recovery, coasting and shifting of the load point – the engine can be operated in a more favourable area of the engine map; load increase/reduction depending on the state of charge of the battery.
Packaging has a lot gain from the new inline configuration. The engine is shorter due to the absence of a belt drive so Mercedes freed more space for ancillary components on either side of the new inline six cylinder unit. Its performance is also as dynamic as that of a V8, as the new six-cylinder in-line engine comes with an especially intelligent form of turbocharging: assisted by the ISG at start-off, the electric auxiliary compressor (eZV) guarantees immediate high torque when driving off and accelerating, bridging the time before the large exhaust turbocharger cuts in. The electric turbocharger accelerates to 70,000 rpm within 300 milliseconds, ensuring an extremely spontaneous reaction from the engine.
The new engine has 2,999 cc and develops more than 408 hp and 500 Nm (versus 2,996 cc and 333 hp for the old M276 V6) while CO2 emissions have gone down by 15%. Another trick used by Mercedes is the first-ever particulate filter to be mounted on a series gasoline engine. It traps soot particles and it will be gradually appear on all future engines, beyond the all-new M256 inline-six cylinder.
OM656 six-cylinder inline diesel with 313 hp
The list of brand new engines continues with a 3-liter diesel, again in the inline-six cylinder configuration. Codenamed OM656, Mercedes says this will be the most powerful six-cylinder diesel in its line-up with ample power output of 313 bhp (up from 258 bhp on the old V6).
The new engine features state of the art design. Mercedes says the inline-six cylinder unit uses an aluminium engine block and steel pistons (reducing the friction by 40 to 50 percent), multi-way exhaust gas recirculation and a near-engine exhaust aftertreatment. Also of great importance is the Nanoslide technology – an extremely thin, low-friction coating of the cylinder walls, two measures that reduce friction.
Another high-tech solution is the stepped-bowl combustion process – named after the shape of the combustion bowl in the piston. The efficiency is increased by the higher burning rate in comparison with the previous omega combustion bowl. The characteristic feature of the specifically configured combination of bowl shape, air movement and injector is its very efficient utilisation of air, which allows operation with very high air surplus. This means that particulate emissions can be reduced to an especially low level.
Fuel consumption has gone down 7%. his is reinforced by the CAMTRONIC switchable exhaust camshaft, which supports the consumption-neutral heating of the exhaust system. The new engine is equipped with multi-way exhaust gas recirculation (EGR). It combines cooled high-pressure and low-pressure EGR. This makes it possible to significantly further reduce the untreated emissions from the engine across the entire engine map, with the centre of combustion being favourable for fuel economy.
M264 four-cylinder petrol with 100 kW per litre
Last but not the least in Mercedes’ engines refresh campaign is the brand-new two-litre inline four-cylinder gasoline unit, codenamed M264). Exact power specs have not been released, but Mercedes claims an output of 100 kW per liter. The M 264 will celebrate its debut next year.
The list of modern technologies incorporated into the new engine features a belt-driven 48V starter-alternator (BSA) that is responsible for for fuel-saving hybrid functions such as energy recovery (up to 12.5 kW) and provides an engine speed boost at low revs up to 2.500 rpm and coasting function with engine off.
The new engine also uses twin-scroll turbocharging that merges the exhaust gas ducts of cylinder pairs in the flow-optimised manifold. This turbocharging concept with systematic cylinder flow separation produces high torque in the low-rpm range together with high specific output.
New engine tech at a glance
48V electrical system
Supplies four times the power of its 12 V predecessor at the same current and allows the electrification of key components (e.g. air-conditioning compressor) or the introduction of new technologies (e.g. electric auxiliary compressor) and therefore fuel savings. The low-voltage system does not require the additional safety architecture of a high-voltage network.
Integrated Starter-Alternator
Combines starter and alternator functions into one electric machine driven not by a belt, but directly by the crankshaft. It is positioned between engine and transmission. Also, an ISG enables hybrid functions, such as boost, energy recovery and stop/start.
Petrol particulate filter
Found only on diesels until recently, these were used by Mercedes-Benz since 2014 in the S 500. These reduce the emissions of particulate matter, especially in directly injected petrol engines. The PPF is made of a material called cordierite, known for heat resistance properties.
Electric auxiliary compressor
This compressor, which is powered by the 48 V electrical system, delivers charge-air pressure independently of engine speed and engine load. Connected in tandem with a large exhaust turbocharger, the eZV ensures a balanced engine response in all rpm ranges and eliminates the turbo lag. Works like a small turbocharger, spinning up to 70,000rpm in 300 milliseconds and delivering pressurised air to the engine, in doing so eliminating the sensation of turbo lag under acceleration.
Belt-driven starter-alternator (BSA)
Combination of starter and alternator, which, like a conventional alternator, is connected to the crankshaft by a belt drive.
