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The Independent Automotive Aftermarket Federation

Bosch: The future for diesel

Date: 10-Mar-2020

How do you solve one of the most pressing problems facing towns and cities? How do you satisfy the population’s desire for cleaner air? And how do you achieve that without restricting the mobility of city dwellers through driving bans? Air quality in towns and cities is a major challenge for all concerned nowadays.

Thanks to new test procedures and engineering ingenuity from Bosch, a decisive technological breakthrough has now been achieved with regard to improving air quality.

The new, enhanced diesel technology will result in a further shift in the limits of what has been feasible so far, leading to a sustained reduction in nitrogen oxide emissions. This technological breakthrough can make the diesel about as clean as a gasoline engine. It means diesel is therefore still an affordable alternative for urban traffic and in the future will be an ecologically sound one too.

The arguments in diesel's favour are:

  • Diesel engines reduce the impact on the climate.  A diesel engine that conforms to the Euro 6 emissions standard emits some 15% less CO2 than a comparable petrol engine.
  • The lower fuel consumption of diesel engines conserves resources and saves frequent drivers money.
  • Diesel remains absolutely essential for achieving the EU's climate targets.  Without diesel, it will be hard to achieve the fuel-efficiency and emissions targets that the EU has set itself for 2020 and beyond.
  • Since the introduction of particulate filters, diesel emissions have effectively ceased to be a factor in particulate pollution in cities.
  • Vehicles that are equipped with state-of-the-art diesel technology will have no discernible negative impact on the amount of nitrogen oxides in city air - regardless of the driver's style of driving or the vehicle's engine temperature.

The air quality in our cities depends on a number of factors.  Combustion engines impair the air quality in cities to a small extent. Emissions are also a by-product of the day-to-day operation of power stations and industrial facilities, to name just two sources. Diesel technology has reached a very high level of development, making the diesel engine one of the lesser factors that contribute to CO2 and particulate pollution. Bosch is working on reducing diesel’s contribution still further. Nitrogen oxide pollution will in the future likewise hardly be attributable to diesel. 

Driving in everyday situations is multifaceted and includes acceleration, gradients, stop-and-go traffic, and high speeds, etc. The European test procedure that has been applicable since September 1, 2017 within the scope of Euro 6d takes into consideration precisely these kinds of driving situations. In the past years, Bosch has actively supported the introduction of this procedure. After all, staying true to its guiding principle of “Invented for life”, Bosch is highly committed to using technologies that conserve our natural resources to the greatest extent possible.

The test specifications include the following:

Drive duration: 90-120 minutes
Route: 1/3 city driving (< 60 km/h), 1/3 highway with speeds of 60-90 km/h, and 1/3 freeway with speeds of 90-145 km/h
Cumulative elevation gain over the test route: < 1,200 m / 100 km

Ambient temperatures: between -7 °C and 35 °C

It quickly became apparent that on-the-road testing leads to more effective solutions. At Bosch, the many new insights have accelerated technological development significantly. Bosch engineers have succeeded in achieving average NOx emissions of 13 mg/km during drives on roads with urban, rural, and freeway elements. With the current state-of-the-art exhaust technologies from Bosch, vehicles are capable of emitting only very little NOx while still preserving the diesel engine’s renowned efficiency. Bosch has been able to demonstrate ways in which the entire powertrain system can be optimized, achieving results that even exceed Bosch’s own expectations. Bosch makes this possible with, for instance, a rapid-response air management system and sophisticated thermal management of the exhaust-gas treatment system. Regarding the air management system: the more dynamic the driving style, the more dynamic exhaust gas recirculation must be as well. Turbochargers that respond more quickly than before meet these requirements. The combination of high- and low-pressure exhaust gas recirculation makes the air management system even more flexible. And regarding the sophisticated exhaust-gas treatment system: Bosch has found a solution in which the starting temperature barely has an effect on emissions anymore.

Up to now, an issue had existed where – under certain driving conditions – the temperatures in the exhaust system could sometimes drop to a level that was too low, which meant that proper functioning could no longer be fully ensured. By establishing a smart link between the engine and exhaust-gas treatment system, it is now possible to take corrective action with foresight. This ensures the exhaust system stays warm enough and can do its job reliably, even in city driving.

An external engineering company analyzed the emissions data collected at the Neckartor in Stuttgart, one of the most critical spots in the whole of Germany. After applying a variety of computational models, it came to the following compelling conclusion: if diesel vehicles equipped with the latest technologies replaced the current diesel fleet, the diesel engine would only be responsible for a negligible portion of the relevant ambient air contaminants.

Bosch has therefore come closer to achieving the goal of a combustion engine that no longer significantly pollutes the air. And that is a revolution for the now more than one-century-old diesel technology.

In terms of the comprehensive well-to-wheel carbon footprint, the combustion engine and electric drive are not as far apart as is generally assumed. One advantage of this approach would be that non-fossil fuels, like paraffinic fuels, can be taken into consideration too. These fuels are made from animal and vegetable waste. Already today, they can be used as an additive of up to 30% volume in blended fuels and could reduce the carbon footprint by up to 25%. As a result, when considered well-to-wheel, the carbon footprint of a modern diesel vehicle would be almost halved with such fuels – from the current 110 g/km to 60 g/km. In the well-to-wheel analysis for electric vehicles, the production of the electric power is also included in the carbon footprint calculation.

Based on the mix of energy sources currently used in Germany for electric power generation, a compact electric car similarly has a carbon footprint of 80 g/km – and when viewed in terms of the European mix, the footprint is still 40 g/km.

It is evident that both technologies are ready for a more environmentally friendly future; although to achieve that, more renewable power is needed for the electric drive and more reduced-carbon fuels are required for the combustion engine. With synthetic fuels there is even the prospect of running the combustion engine with a net zero carbon footprint. Bosch will continue to press ahead with the development of environmentally friendly powertrain systems to further improve air quality.

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