Paper by Dr. Rolf Leonhard Executive Vice-President Engineering Diesel Systems" />

Mobility Solutions

Reducing CO2 emissions with optimized internal-combustion engines Paper by Dr. Rolf Leonhard Executive Vice-President Engineering Diesel Systems

  • at the 60th Automotive Press Briefing in Boxberg, June 2011
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  • June 09, 2011
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press release

Ladies and gentlemen,

The internal-combustion engine will to continue to play a major role in the future of personal mobility, and will have to contribute to the protection of the world’s climate and the conservation of our limited reserves of fossil fuel. That is the conclusion to be drawn from the studies conducted both by our own market researchers and by external specialists into the development of the global automotive market.

Our forecasts tell us that by 2020 annual demand for cars and light trucks will reach 103 million units. Of these, only 3 million will be either all-electric vehicles or plug-in hybrids. A further 6 million will be hybrid vehicles with an electric drive in addition to their internal-combustion engine. In other words, a good 100 million new vehicles powered by internal-combustion engines will be sold in 2020.

Our forecasts also show that 30 million more new cars with internal-combustion engines will be sold in 2020 than the 71 million that were sold last year. In other words, the market for vehicles with internal-combustion engines will grow by a good 40 percent over the next ten years.

CO2-targets only achievable via optimized combustion engines
How then, in spite of this, can we hope to achieve society’s goals of protecting the environment and conserving fossil-fuel reserves? The answer is easy to work out: all-electric vehicles and plug-in hybrids help reduce CO2 emissions by roughly 4 grams per kilometer. So the role of the 97 percent of new vehicles with internal-combustion engines will have to be decisive.
And the pressure on engineers will increase as target figures for CO2 emissions become tighter around the world over the next ten years.

These days, there are either agreed targets or legally binding values for CO2 emissions in many countries all over the globe. In 2009, the average passenger car in Europe had carbon dioxide emissions of 146 grams per kilometer. The European Commission has set its member states the goal of reducing emissions by 11 percent to 130 grams by 2015. By 2020, CO2 emissions should be reduced further to a target of 95 grams, which represents a cut of 35 percent from 2009 levels. The Commission’s target for 2025 is for the average new vehicle to emit 70 grams of CO2 per kilometer. This equates to fuel consumption figures of around three liters of gasoline or 2.6 liters of diesel per 100 kilometers – a good 50 percent less than today’s average. Another way to express the figures is to say that gasoline engines will have to achieve a good 78 miles per gallon and diesel engines 90 miles per gallon. The Commission has also set targets for light trucks up to 3.5 metric tons for 2020: the stipulated figure of 147 grams of CO2 per kilometer represents a reduction of around 30 percent.

Biofuel – different markets, different targets
Depending on regional circumstances, markets vary in the technical focus of their efforts to reduce CO2 emissions. In Brazil, for example, an important role is played by flex-fuel technology. There exists a large production of sugar cane, which is then converted into ethanol. This ethanol serves as an alternative to fuels derived from crude oil. The fact that this fuel is made from renewable raw materials means it has a notable positive impact on carbon footprint.
In the United States, more and more flex-fuel vehicles are being registered that can run on gasoline blends with up to 85 percent ethanol. Other countries and regions also take advantage of this eco-friendly effect by blending biogenic and fossil fuels – with blending levels of between 5 and 20 percent for both gasoline and diesel. In future, synthetic fuels based on organic waste materials will also gain in significance.

Diesel plays a major role in fuel economy
In Europe, car drivers and the automotive industry regard diesel as a solution, with half of all vehicles using this fuel-efficient and hence low-CO2 technology. India is also a strong market for diesel. In the United States, gasoline engines will continue to be the powertrain of choice, with only a small but growing segment of drivers opting for diesel-powered cars. In China, the world’s fastest-growing automotive market, currently over 99 percent of newly registered cars run on gasoline. Three percent of minibuses are diesel-powered, while three-quarters of newly registered light commercial vehicles are fitted with a diesel engine. Overall, we are expecting a shift toward more diesel engines as well as growth in electric vehicles, since the Chinese government is also aiming for low-CO2 mobility – albeit without specifying a preferred technology.

Even if views of which vehicle fuel is best for the environment differ around the world, there is nonetheless only one way forward. The key to reaching the CO2 targets that have been set for 2025 lies in the internal-combustion engine, but increasingly also in hybrid powertrain concepts.

At the 2009 Automotive Press Briefing, Bosch elaborated on this point: over the medium term, the fuel consumption and CO2 emissions of internal-combustion engines will drop by
30 percent – both for gasoline and for diesel engines. In addition, hybrid powertrains offer the chance to reduce consumption and CO2 emissions by a further ten percent. Taken together with the modifications automakers are making to vehicles themselves – including low-resistance tires, lightweight construction, and reductions in drag – this means fuel consumption and CO2 emissions can be reduced in total by around half from today's average level.

CO2-targets for 2020 are reachable
In other words, the European CO2 target for 2020 of 95 grams per kilometer is feasible for vehicles with internal-combustion engines. Bosch offers the automotive industry technology packages with which to achieve the major savings required in both diesel and gasoline engines.

If we consider the standard consumption of new vehicles in the European market more closely, we see that a number of vehicle models are already within the 2015 CO2 limit – including some midsize cars. For instance, in the compact car class, the VW Golf TSI with its 77-kilowatt gasoline engine and 121 grams of CO2 emissions consumes 5.2 liters of fuel per 100 kilometers. The same Golf fitted with a diesel engine manages 99 grams or 3.8 liters. The Volvo C30D also emits 99 grams from its 84-kilowatt engine.

But even in the upper mid-size category, the BMW 5-series manages just 4.9 liters or 129 grams with its 135 kilowatts of engine output.
The gasoline-powered Peugeot 508 emits 144 grams, while the VW Passat emits 138 grams. Toyota’s gasoline hybrids set the standard in the compact class, with CO2 emissions of around 90 grams, depending on the model. Looking at heavier vehicles, new diesel hybrid models have been announced that meet the CO2 targets for 2020 – such as the Peugeot 3008 featuring Bosch hybrid technology.

If we look closely at the figures, we see that gasoline hybrids have standard consumption values that are close to those of comparable diesel vehicles. Both technologies are already capable today of meeting the target levels that are being discussed for 2020.

These interesting examples of current automotive industry products show that our forecasts are realistic. Having said that, most engine designs currently in series production offer plenty of scope for consumption-reducing technologies that ultimately allow the desired fleet limits to be met. And the stock of technical improvement options we described in 2009 is by no means exhausted – even for the particularly low-consumption vehicles I mentioned just now.

Downsizing – the key to saving fuel
In terms of the engine itself, the most effective measure is downsizing. Reducing displacement and the number of cylinders reduces friction losses and means less moving mass. An engine of this kind also has fewer thermal losses. It is the job of engine developers to reduce displacement, and also the number of cylinders where appropriate, while maintaining or increasing engine performance.

An engine's performance can be maintained, even if developers reduce the displacement and the number of cylinders, as long as more air is directed to it per combustion cycle than it is able to draw for itself. This is made possible by turbocharging, which provides the engine with the volume of air needed to ensure clean combustion.

From the end of 2011, Bosch‘s joint venture Bosch Mahle Turbo Systems will produce modern turbocharger systems which are designed specifically for these new gasoline and diesel engine concepts for passenger cars and commercial vehicles. We expect our joint venture to produce one million of these performance-optimized turbochargers in 2015.

The limits to downsizing are not fixed for displacement or for the number of cylinders. In the end, engineers must see to it that they improve efficiency while achieving an acceptable balance between fuel efficiency, cost, driveability, and convenience.

They can go about this through downsizing, which aims to in-crease performance per liter of displacement. In gasoline engines, this must overcome what is known as the knock limit, at which fuel ignites in an uncontrolled fashion and can cause engine damage. Engineers can use gasoline direct injection to cool the combustion chamber and at the same time achieve good scavenging without fuel losses in the gas-exchange cycle. In this way, the knock limit can be pushed toward higher loads and degrees of supercharging. The result is impressive torque figures even at low engine speed, something that was only possible with diesel engines before.

Even the economical diesel still has potential
In diesel engines too, the potential of downsizing has still not been exhausted. As charge-air pressure through the turbocharger rises, our developers need to increase the injection pressure of the common-rail system as well. This higher injection pressure brings many benefits. It means more diesel fuel can be injected in the same time, which allows a better power yield because the specific power of the diesel engine increases. Alternatively, engine developers can reduce the diameter of the nozzle holes in the injectors while maintaining engine power. When combined with multiple pre-and post-injections, this improves mixture formation in the combustion chamber, saves fuel, and leads to cleaner exhaust emissions. This is a particularly effective way of reducing nitrogen-oxide emissions.

Engineers also take advantage of higher injection pressure in order to prevent rising cylinder pressures and peak exhaust gas temperatures at high levels of turbocharging from placing greater strain on the engine design.

Bosch will start series production of the first 2,200 bar common-rail system for passenger cars later this year. And Bosch engineers are already working on a 2,500 bar common rail. Even at these high injection pressures, we are not encountering any technological barriers, although the engineers are having to display ever finer technical prowess to achieve these advances without increasing space and weight and without losing hydraulic efficiency.

Today’s passenger cars already comply with the Euro-6 standard for 2015
Even if injection pressure in common-rail systems rises further, this pollution-reducing measure is by no means necessary in all engines. In addition to diesel particle filters, engineers can now turn to systems that reduce nitrogen oxide emissions. The first passenger car systems have been in series production since 2008 in the United States and since 2009 in Europe. These diesel vehicles already comply with the Euro 6 standard that will apply from 2015.

These DeNOx systems allow compliance with future higher emissions requirements at injection pressures of 1,600 bar. As use of common-rail systems increases in Asian growth markets, which demand particularly robust but affordable solutions, we will equip systems in China and India with injection pressures between 1,400 and 1,800 bar.

In diesel passenger cars, NOx exhaust gas treatment can also be used to reduce the fuel consumption of the internal-combustion engine by up to 5 percent.

Bosch engineers are increasingly complementing all the technical measures being applied directly to gasoline and diesel engines with more efficient auxiliary systems. Additional CO2 improvements can be achieved by making systems demand-driven – so that they are only operated or used when they are really needed. Electrically driven water pumps, electric power steering, and generators that recharge the battery primarily when coasting serve to improve the vehicle’s overall efficiency. One particularly effective example is the Bosch start-stop system. It stops the engine at a red light and restarts it reliably when the lights turn green. In the New European Driving Cycle, this achieves a saving of some 4 percent, and as much as 8 percent in urban driving.

Tomorrow’s technology already available today
Bosch today offers the automotive industry a whole series of components and systems that contribute significantly to more economical driving and reduced CO2 emissions. For this reason, vehicles are already in production with modern internalcombustion engines that come very close to policymakers’ targets. In other words, the fleet consumption targets for 2020 are reachable with modern technology.

Based on typical annual mileages for Europe and today's fuel prices there, a comparison of the fuel consumption of the average car in 2010 with a car built in 2020 shows fuel cost savings over three years of operation of between 1,000 and 1,500 euros. In other words, drivers’ operating costs are likely be reduced by more than enough to cover the cost of all the extra technology they will have to buy in 2020 to make their cars more economical. If we consider a normal vehicle service life of some 12 years, this amounts to fuel savings of 4,000 to 6,000 euros and a reduction in CO2 emissions of between 6 and 11 metric tons.

Looking beyond the range of technologies that already exist for reducing fuel consumption and CO2 emissions, Bosch engineers are busy looking for ways to tap further savings potential – both in gasoline and in diesel engines. In both diesel and gasoline engines, they are studying measures such as combustion control using combustion chamber pressure sensors.
Or they are looking at variable valve control for diesel engines, not just for gasoline engines as is the case today. Work could also be done on transmissions to increase the efficiency of the automotive system, on energy recovery from exhaust heat, or on reducing the need for cooling.

Thank you for your attention.

RF00116 - June 09, 2011

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