Mercedes-Benz DIRECT HYBRID and BLUETEC HYBRID

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• Mercedes-Benz Advanced Power
• Pioneering drive concepts: Environmentally friendly, economical and dynamic

Mercedes-Benz is presenting two unique drive concepts at the International Motor Show 2005 in Frankfurt. In two concept cars � “DIRECT HYBRID� and “BLUETEC HYBRID� � each based on the new S-Class, the most efficient and environmentally friendly designs from the world of petrol and diesel engines are combined with a hybrid. While offering the maximum environmental compatibility, these vehicles simultaneously guarantee good driving dynamics and ride comfort.

At the start of the 21st century, it is becoming clear that, despite the merit of the fuel cell as a long-term prospect, the internal combustion engine will continue to play a major role over the medium term. It will therefore remain a central focus for the efforts of the Mercedes engineers in the coming years � in both its petrol and diesel forms. In both cases, the objective is to make still further improvements in fuel consumption and environmental compatibility. As a manufacturer of high-quality cars, Mercedes-Benz is shouldering its social responsibility in this respect. Moreover, the company sees a special obligation in the fact that it is a technological leader.

The petrol engine is becoming more economical

In the case of the petrol engine car, the main emphasis of development is on further reducing fuel consumption. Its advantages � high performance and outstanding ride comfort at low costs � will naturally be preserved. Since 2003, petrol engines have been meeting the emissions standards now in effect in Europe and the USA, since this year including the SULEV (Supra Ultra Low Emission Vehicles) standard, and Mercedes-Benz is also well-equipped to deal with forthcoming, more stringent exhaust emissions limits.

Compared with the diesel, the petrol engine still harbours considerable potential for reductions in consumption. With the second generation of the spray-guided petrol direct injection system, the engineers at Mercedes-Benz have achieved a crucial innovation that allows considerable improvements in fuel consumption. Using the current 3.5-litre, 4-valve V6 with fully variable valve timing as the basis, this technology was implemented in the Vision S350 “DIRECT HYBRID.�

Compared with the first-generation direct injection designs, the latest combustion process from Mercedes-Benz offers a significant improvement in fuel consumption and engine performance merely by ensuring the formation of a stable fuel spray through the injection nozzle. For the spray-guided combustion process, engineers developed a special piezo injection valve and a fuel system with a high pressure of 200 bar. The stability of the injection spray � one of the critical aspects of the process � is ensured by a special injection nozzle that opens to the outside and is activated at ultra-high speeds by a piezo crystal. The quantum leap of this innovative process lies in the control of the fuel spray and the extremely rapid timing of the piezo nozzle, which allow the formation of a fuel-air mixture with the ideal flammability. The thermodynamic efficiency improves markedly and enables low fuel consumption with better engine performance. With the innovative direct injection process, the 3.5-litre V6 in the “DIRECT HYBRID� generates an output of 215 kW (292 hp) at 6,000 rpm. Its maximum torque of 365 Nm is already accessible at 2,400 rpm and remains available over a broad range of engine speeds up to 5,000 rpm.

The exhaust treatment for this layered direct injection process takes place in the double-stream exhaust system. A NOx trap system for reducing the nitrogen oxides is also used, in addition to the two bulkhead catalytic converters and controlled recirculation of exhaust gas in each branch. It is thus possible to achieve extremely low exhaust emissions levels, which naturally satisfy the current EU 4 exhaust emissions standards and the forthcoming EURO 5 limit.

The design is rounded out by another technological feature that helps reduce consumption and also contributes to driving enjoyment � the built-in high-torque electric motor.

The built-in electric motor - a boost for the environment, fuel efficiency and comfort

This particular solution is what makes the two concept cars “mild hybrids�. To save space, the electric motor is installed between the engine and the 7G-TRONIC automatic transmission’s converter. Depending on the driving situation, it functions as a starter or a generator. This is particularly advantageous in the heavy traffic of an urban area, because it makes it easy to create an automatic stop-and-go transmission that alone can save three to six per cent of fuel under these circumstances. A quick touch of the accelerator and the electric motor smoothly brings the engine back to life. At the same time, the electric motor supplies a maximum of 250 Nm to the drive power during starting. It thus provides optimal support for the combustion engine which � as a consequence of its operating principle � first builds up its torque as the revs increase. The combination of motor and engine boosts the maximum available torque to 395 Nm and makes the vehicle’s starting characteristics powerful.

The electric motor concept unfolds its greatest potential in heavy stop-and-go traffic. Despite its dynamic acceleration (0 – 100 km/h in 7.5 seconds) the “DIRECT HYBRID� uses just 8.3 litres of petrol per 100 km in the European Driving Cycle. The advantages of this impressive technology package add up to an impressive result: Compared with its predecessor model, the S 350 V6 (W 220), the power has been increased by 19 per cent and the consumption cut by an impressive 25 per cent.

By reversing its function, the electric motor can also regain a portion of the vehicle’s kinetic energy during phases of coasting without acceleration and when engaged in regenerative braking. This energy is stored in a new type of rechargeable high-performance battery using lithium ions. Energy storage devices of this type are distinguished by their high power density, and can charge and discharge electrical energy extremely rapidly. At the same time, Mercedes-Benz is also investigating the use of high-performance capacitors known as ultracaps. Both of these energy storage devices can contribute a few percentage points towards fuel savings, depending on the application profile.

Diesel with “BLUETEC� and hybrid unites driving pleasure, economy and ecology

The latest concept car, the “BLUETEC HYBRID,� also presented by Mercedes-Benz in an S-Class at the IAA, even goes a step further. This vehicle unites a maximum of emissions reduction technology with the diesel’s typical advantages of economy and agility and the consumption technology of a mild hybrid. Like the “DIRECT HYBRID� petrol variant, the “BLUETEC HYBRID� uses an additional 6 kW/8.2 hp electric motor, which serves both as starter and as starting booster. It can also be used for regenerating power from kinetic energy. The basic drive of the “BLUETEC HYBRID� is the 3 litre V6 diesel engine, a variant of the 320 CDI with 173 kW/235 hp of output and a maximum torque of 540 Nm that is already available at between 1,600 and 2,400 rpm. “BLUETEC� offers a technology with which the diesel can also meet future emissions values in Europe, the USA and Japan. This technology package can achieve consumption figures of 7.7 litres /100 km in the European Driving Cycle. Compared to the S-Class predecessor model (S 400 CDI/W220) which was itself unusually economical, this represents a further saving of 20 per cent for comparable power and torque. Driving pleasure, economy and ecology are the distinguishing features of this concept car and will not cause contradictions at Mercedes.

“BLUETEC� � the world’s cleanest diesel

Thanks to its future-oriented research and development with “BLUETEC� technology (selective catalytic reduction, SCR), Mercedes-Benz is excellently equipped to meet future emissions requirements in Europe, Asia and the USA. “BLUETEC� has already been fitted to more than 5,000 Mercedes-Benz commercial vehicles such as the Actros und the Axor in customer’s fleets. “BLUETEC� has reduced their emissions of nitrogen oxides by around 80 per cent. This means that these vehicles already fulfil the EURO 5 exhaust gas standards, which will first become binding in 2009 for trucks. The precondition for this is the targeted and measured addition of “AdBlue� � an aqueous carbamide solution � into the exhaust line. This reacts with the nitrogen oxides in the catalytic converter to form ammonia (NH3) as an intermediate product which then is converted into the harmless natural products of water and nitrogen. In Europe, the supply network for “AdBlue� already includes 400 filling stations. Mercedes-Benz now intends to utilize the vast potential of this technology for diesel passenger cars too, and is currently carrying out tests on such vehicles worldwide. “BLUETEC� is available now and is currently the best technology for reducing emissions of nitrogen oxides � it can even be used to meet the planned stricter emissions guidelines in California.

The AdBlue must be metered precisely according to the driving situation in order to always achieve the maximum catalytic converter conversion rates. The customer, however, doesn’t need to worry about that. In order to guarantee keeping within the NOx exhaust emissions limits over the normal service interval, a 22-litre tank has been built into the spare-wheel well of the S Class. Average AdBlue consumption is around 0.1 litre per 100 kilometres. Should the supply run out before the next service, a signal in the instrument cluster warns the driver to visit a service station in plenty of time. This tank is therefore sufficient for the driving distance between two service intervals and the service personnel simply fill the tank up automatically when the car goes in for its next service.

Mercedes-Benz has set itself the objective of building the world’s cleanest diesel, and christened it “BLUETEC.� Diesels should be as clean as petrol engines as far as emissions are concerned, and thus ready for future emissions regulations worldwide. The company is following a three-stage plan to accomplish this:

• Internal measures to make the combustion process as efficient and clean as possible.
• Oxidation catalytic converters lower the carbon monoxide and hydrocarbon emissions and particulate filters cut the particulate emissions to a barely measurable level.
• “BLUETECâ€ÂÂÂ� technology will reduce emissions of nitrogen oxides â€â€ÂÂ� the last remaining exhaust gas constituent that is still present in higher levels than in petrol engine exhausts â€â€ÂÂ� by 80 per cent.

This can fulfil even the strictest exhaust emission limits currently under discussion and so secure the future of the diesel drive in markets such as the USA and Japan.