The New Mercedes-Benz E-Class Cabriolet: the Drive System
Mercedes-Benz has taken further strides forward to reduce fuel consumption and exhaust emissions without compromising
by Thomas Philips | 09 March 2010
With its newly developed direct-injection diesel and petrol engines, Mercedes-Benz has taken further strides forward in its quest to reduce both fuel consumption and exhaust emissions – without compromising on agility and driving enjoyment. The line-up of powerful and extremely efficient drive units available at sales launch ranges from the E 220 CDI BlueEFFICIENCY developing 125 kW (170 hp) to the E 500 developing 285 kW (388 hp). All of the powerplants meet the requirements of the EU 5 standard, whose limits are up to 80 percent more stringent than those specified by previous standards.
The four-cylinder diesel engine in the E 250 CDI BlueEFFICIENCY model, for example, shows just how much progress has been made: with an output of 150 kW (204 hp), a peak torque of 500 Nm and a displacement of 2.2 litres, it delivers outstanding performance yet consumes only 5.6 litres of fuel per 100 kilometres (NEDC combined figure). What’s more, CO2 emissions are just 148 grams per kilometre. All of which means that the new CDI Cabriolet is more fuel-efficient than comparable models in this output category.
Diesel engines: new four-cylinder unit featuring state-of-the-art common-rail technology
As well as being economical and ecofriendly, the four-cylinder CDI engine impresses with its exceptional agility, as reflected in the performance figures: the new E 250 CDI BlueEFFICIENCY Cabriolet takes 7.8 seconds to accelerate from 0 to 100 km/h.
Like the E 220 CDI BlueEFFICIENCY unit, this engine is part of the new series of four-cylinder powerplants, which saw Mercedes-Benz introduce the fourth generation of its tried-and-trusted common-rail direct-injection system into series production. One of its hallmarks is a 400-bar increase in the maximum rail pressure, which now stands at 2000 bar.
Newly developed piezo injectors are key components in the latest CDI engine generation. They use piezoceramic properties to change their crystal structure – and therefore their thickness – in a matter of nanoseconds when electrical voltage is applied. The new injectors are equipped with a stack of thin piezoceramic layers (called the “piezo stack”) to enable them to achieve a sufficient overall lift from the very small lift per layer.
In contrast to the systems commonly used to date, this lift activates the nozzle needle directly, so that the fuel injection can be adjusted even more precisely in line with the current load and engine-speed situation – for example by means of precise multiple injections, which have a favourable effect on emissions, fuel consumption and combustion noise.
The new diesel engine in the E 250 CDI BlueEFFICIENCY model marks the debut of two-stage turbocharging in a series-production diesel engine for Mercedes-Benz passenger cars. The aim is to achieve a further improvement in start-up performance and peak output.
Six-cylinder CDI: increased output and fuel consumption of 7.0 litres per 100 kilometres
The V6 diesel engine for the E 350 CDI BlueEFFICIENCY is one of the most sophisticated compression-ignition units on the world market. It offers greater output, comfort and driving enjoyment than other engines thanks to the immense torque of 540 Nm alone, which is available between 1600 and 2400 rpm, ensuring outstanding agility when accelerating from rest and exemplary flexibility when accelerating in any gear: the car accelerates from 0 to 100 km/h in 6.9 seconds. The six-cylinder unit has an output of 170 kW (231 hp).
Despite the high output and torque, fuel consumption is just 7.0 litres per 100 kilometres, equivalent to 185 grams of CO2 per kilometre. The 7G-TRONIC seven-speed automatic transmission is specified as standard for the E 350 CDI BlueEFFICIENCY.
The Mercedes engineers have gone to great lengths to optimise the technology at the heart of the V6 diesel engine, reducing the compression ratio from 17.7 to 15.5, combined with an enhanced turbocharger, ceramic glow system, modified injection nozzles and optimised air ducting.
The range of diesel engines for the E-Class Cabriolet at a glance:
|E 220 CDI BlueEFFICIENCY||E 250 CDI BlueEFFICIENCY||E 350 CDI BlueEFFICIENCY|
|Engine/cylinders||Diesel/4 in-line||Diesel/4 in-line||Diesel/V6|
|Transmission fitted as standard||6-speed manual||6-speed manual||7-speed automatic|
|Displacement||2143 cc||2143 cc||2987 cc|
|Rated output||125 kW (170 hp)||150 kW (204 hp)||170 kW (231 hp)|
|Rated torque||400 Nm at
|500 Nm at
|540 Nm at
|Fuel consumption*||5.4 l/100 km||5.6 l/100 km||7.0 l/100 km|
|CO2 emissions**||143 g/km||148 g/km||185 g/km|
|Emission standard||EU 5||EU 5||EU 5|
*NEDC combined fuel consumption;** NEDC
Petrol engines: new four-cylinder unit with direct injection
CGI appears at the end of the model designation of the four- and six-cylinder petrol engines for the new E-Class Cabriolet, signifying that Mercedes-Benz uses direct petrol injection for all of these powerplants. The entry-level model is the E 200 CGI BlueEFFICIENCY developing 135 kW (184 hp), with an automatic transmission fitted as standard. This model will also be available with a 6-speed manual transmission and standard-fit ECO start/stop function from June 2010.
Compared to conventional port injection, direct fuel injection allows higher compression and, therefore, improved thermodynamic efficiency, saving motorists money at the pump: the four-cylinder direct-injection engine in the second most powerful CGI model, the E 250 CGI BlueEFFICIENCY, consumes just 7.9-8.2 litres per 100 kilometres, with an output of 150 kW (204 hp) and a peak torque of 310 Nm. Mercedes-Benz equips the Cabriolet featuring this engine with a five-speed automatic transmission as standard.
Six-cylinder engine: CGI technology with spray-guided combustion
The E 350 CGI BlueEFFICIENCY Cabriolet is powered by the world’s first petrol engine to feature spray-guided combustion. The six-cylinder powerplant develops 215 kW (292 hp) and provides a peak torque of 365 Nm from 3000 rpm.
Thanks to the state-of-the-art engine technology, fuel consumption is reduced to 8.8 litres per 100 kilometres (NEDC combined figure). The seven-speed automatic transmission comes as standard. What’s more, the highly economical and environmentally compatible CGI powerplant provides a unique driving experience: it takes the V6 Cabriolet 6.8 seconds to accelerate from 0 to 100 km/h.
Precision-modified eight-cylinder engine
The eight-cylinder unit in the E 500 Cabriolet is the flagship powerplant, providing a blend of high output and torque yield with exemplary refinement and effortlessly superior agility. The extent of the powerplant’s capability is highlighted by the performance figures for the top-of-the-range model, which is equipped with the 7G-TRONIC seven-speed automatic transmission as standard: 0 to 100 km/h in 5.3 seconds.
The key data for the E-Class Cabriolet petrol models:
|E 200 CGI BlueEFFICIENCY||E 250 CGI BlueEFFICIENCY||E 350 CGI BlueEFFICIENCY||E 500|
|Engine/cylinders||Petrol/4 in-line||Petrol/4 in-line||Petrol/V6||Petrol/V8|
|Transmission fitted as standard||5-speed automatic||5-speed automatic||7-speed automatic||7-speed automatic|
|Displacement||1796 cc||1796 cc||3498 cc||5461 cc|
|Rated output||135 kW (184 hp)||150 kW (204 hp)||215 kW (292 hp)||285 kW (388 hp)|
|Rated torque||270 Nm at
|310 Nm at
|365 Nm at
|530 Nm at 2800-4800 rpm|
|Fuel consumption*||7.9 l/100 km||7.9 l/100 km||8.8 l/100 km||11.0 l/100 km|
|CO2 emissions**||185 g/km||185 g/km||206 g/km||257 g/km|
|Emission standard||EU 5||EU 5||EU 5||EU 5|
*NEDC combined fuel consumption;** NEDC