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Mercedes-Benz debuts new engines in S-Class

Six packed: The inline six-cylinder engine returns to Mercedes-Benz for the first time since 2002, in both diesel and petrol variants.

Mid-life refresh for S-Class sedan marks launch of two important new Benz motors

Mercedes-Benz logo20 Jul 2017


MERCEDES-BENZ’s pair of new inline six-cylinder engines will make their debut under the bonnet of the updated S-Class sedan, with both the diesel and petrol variants packing a host of industry-first technology that is aimed at staying one step ahead of ever-more onerous emissions regulations.

As well, Mercedes-Benz claims that the new diesel engine is the most powerful oiler it has ever produced.

The four new engines will debut in the facelifted S-Class sedan that is expected to land in Australia in December this year.

Local specifications are expected to be confirmed just prior to launch, according to Mercedes-Benz Australia/Pacific manager of public relations and product communications Jerry Stamoulis, but all four variants of the two new engines are expected to arrive in Australia.

“We’re still waiting on timing for the S500,” said Mr Stamoulis. “We’re not sure what we can get in terms of short- and long-wheelbase versions. We’ll also be taking the S450 in long-wheelbase form. We’ll just have to wait and see.”

He also confirmed that the diesel pair is expected to make up 50 per cent of S-Class sales in Australia.

Ironically, the launch of the new engines come as Mercedes-Benz deals with the fallout of accusations by German government officials in Stuttgart that its diesel vehicles are under suspicion of exceeding claimed emissions levels.

The company announced it is recalling up to three million diesel cars in Europe for rectification work on the eve of the S-Class launch. Mr Stamoulis would not comment on whether the recall would impact Australian cars.

The new inline six-cylinder engines – the company’s first since 2002 – are directly related to the brand’s four-cylinder inline family, allowing Mercedes-Benz to cast one set of engine blocks rather than two.

The all-alloy petrol engine – known as the M256 – is bored to 2999cc of swept capacity, and features twin cams, 24 valves and direct fuel injection, and is also fitted with a new electric compressor that is designed to work with a twin scroll turbocharger.

The electric compressor essentially acts as a pre-charger for the turbocharging circuit, adding up to seven PSI of boost in as little as 0.3 seconds to reduce turbo lag.

An industry-first electrical system that creates 48 volts DC powers the compressor, before a converter downgrades that voltage to a more traditional 12 volts to power the car’s other systems.

Integral to the electrical system is the generator that develops those 48 volts, which is located between the engine and gearbox. Called the Starter Generator in Benz nomenclature, the unit not only produces the high voltage numbers required of the electric compressor, but it also recovers energy from off-throttle coasting and can supplement the petrol engine with up to 244Nm of torque for short periods.

That extra hybrid power is stored in a 1kWh 48V lithium-ion battery that is installed in the car, along with a traditional lead-acid 12V unit. The 48V system also controls the car’s air-conditioning compressor, and offers engineers the ability to fit new chassis control technology that requires more power to operate.

The inherent design of the straight-six engine has allowed Mercedes-Benz to package the more sensitive electrical components on the non-exhaust side, or ‘cold’ side of the engine, while the turbocharger is mounted on the same side as the exhaust manifold, or the ‘hot’ side.

It will be offered in two states of tune the lower grade will provide 270kW and 500Nm in the S450, while the higher spec engine in the S500 will provide 320kW and 520Nm.

Both engines are rated in Europe as consuming 6.6 litres of fuel per 100km while emitting just 150 grams of CO2 per kilometre.

Both variants are capable of propelling the S-Class to 100km/h in less than five seconds. The S450 4Matic takes 4.9 seconds, while the S500 is a tenth better at 4.8s.

The new 2925cc inline six-cylinder diesel, meanwhile, will also be offered in two states of tune for the S350d and S400d variants.

A 210kW/600Nm version will power the S350d, while a 250kW/700Nm variant will feature in the S400d.

The diesel has twin-stage turbocharging, variable valve control and a stepped bowl design on top of its steel pistons for better combustion. The block itself is alloy, and is lined with a material similar to that used on the company’s Formula One engines to minimise friction.

Mercedes-Benz also notes that the engine is designed to meet incoming real-world emissions testing regulations – known as Euro 6.c – and that all parts relevant to emissions controls are mounted directly to the engine.

Emissions control equipment can theoretically be mounted anywhere in the driveline, with some elements offering the ability to be mounted inside a transmission, for example.

Mercedes has rated both diesels at 5.1 litres per 100km on the combined cycle in rear drive form and 5.5L/100km in 4Matic spec, with CO2 emissions of 134 and 145g/km on S350d, and 135 and 147g/km for the higher spec S400d.

The all-paw S400 can dash to 100km/h from rest in 5.2s, while the S350d takes 5.8s.

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