Mercedes working on E-turbo

MERCEDES-BENZ product development experts have confirmed they are working on Audi-style electric-powered forced induction systems for new-generation high-performance, fuel-efficient engines with greatly reduced turbo lag.

While they say the jury is still out on the benefits and costs of the technology over exhaust-powered turbocharging, they say they are well down on the track in the development program.

They have not ruled out introducing battery-powered blowers on a new inline six-cylinder family that will replace current V6 petrol engines, probably from 2017.

Rival Audi is already taking the electric turbo route, announcing such a solution for its new diesel SQ7 TDI SUV.

Rather than wait for exhaust gasses to get the turbo spinning, an electric motor spools up the blower at low revs, giving the engine almost instant torque without any power losses.

But one Mercedes insider at the S-Class Cabrio media launch in France told GoAuto that cost-benefit analysis of electric forced induction was still being done.

An extra battery – most likely 48-volt lithium-ion – is just one of the factors that have to be considered in the cost equation against benefits such as greater efficiency and improved control to reduce the major weakness of conventional turbos – lag at low engine speeds.

Company insiders ruled out the introduction of such technology in the immediate future, saying that if it went ahead, the new inline six-cylinder petrol engine already confirmed by Mercedes could be a contender for it.

That engine is not expected to appear in production before 2017 when it will progressively replace V6 engines in Benz large vehicles such as the E-Class, S-Class, GLE and GLS, as well as some AMG variants.

The new engine will be built in two sizes – 3.0 litres for most applications and a special 2.0-litre version for China where large engines are heavily taxed.

The 3.0-litre engine will be a modular design, with pistons, conrods and cylinders built to a 500cc formula that can be shared with a 2.0-litre four-cylinder engine.

Potentially, the 2.0-litre version could also spawn 1.3-litre four and 1.0-litre three-cylinder engines.

However, rumours that Mercedes-AMG might join two of the 3.0-litre engines together to form a new V12 were knocked on the head by engineers who said that was not in the program.

They say they will continue selling the current 6.0-litre V12 “as long as customers want it”, but they also have one eye on stringent new fuel economy and emissions regulations that will bring pressure on big petrol engines.

Mercedes has opted to return to an inline design for its sixes for reasons of superior NVH (noise, vibration and harshness), as well as performance and production ease.

Rival BMW always continued the inline form for its famous six-cylinder cars, while Audi went with V6, variously with supercharging, turbocharging or both.

Mercedes’ new inline engine might have been on the market a little earlier except that the company gave R&D priority to the new alloy-block four-cylinder diesel that is just making its debut in the all-new E-Class large car.

Dubbed E220d, the new variant sips just 3.9 L/100km and emits just 102 grams of CO2 per kilometre – a drop of 13 per cent over it predecessor.

Power is up from 125kW to 143kW, while torque is steady at 400Nm.

Meanwhile, a four-cylinder petrol engine being jointly developed by Daimler and the Renault-Nissan Alliance is also somewhere in the background for future launch.