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Bosch says it has solved diesel NOx problem; as low as 13 mg NOx/km even under RDE; refining existing technologies

Bosch says that its engineers have refined existing diesel technolgoies to reduce emissions of nitrogen oxides (NOx) so significantly that they already comply with future limits. Even in RDE (real driving emissions) testing, emissions from vehicles equipped with the newly premiered Bosch diesel technology are not only significantly below current limits but also those scheduled to come into force from 2020 (Euro 6d).

Because the solution leverages existing technology, there is no need for additional components, which would drive up costs.

There’s a future for diesel. Today, we want to put a stop, once and for all, to the debate about the demise of diesel technology. Bosch is pushing the boundaries of what is technically feasible. Equipped with the latest Bosch technology, diesel vehicles will be classed as low-emission vehicles and yet remain affordable.

—Bosch CEO Dr. Volkmar Denner

Since 2017, European legislation has required that new passenger car models tested according to an RDE-compliant mix of urban, extra-urban, and freeway cycles emit no more than 168 milligrams of NOx per kilometer. As of 2020, this limit will be cut to 120 mg. But even today, vehicles equipped with Bosch diesel technology can achieve as little as 13 milligrams of NOx in standard legally-compliant RDE cycles. That is approximately one-tenth of the prescribed limit that will apply after 2020.

Even when driving in particularly challenging urban conditions, where test parameters are well in excess of legal requirements, the average emissions of the Bosch test vehicles are as low as 40 milligrams per kilometer.

Bosch engineers have achieved this decisive breakthrough over the past few months. A combination of advanced fuel-injection technology, a newly developed air management system, and intelligent temperature management has made such low readings possible, Bosch says.

Overview of temperature management measures for the exhaust system. From the Bosch paper presented at the Vienna Motor Symposium this year. Click to enlarge.

To date, two factors have hindered the reduction of real-world NOx emissions in diesel vehicles, according to Bosch. The first of these is driving style.

The technological solution developed by Bosch is a highly responsive air-flow management system for the engine. A dynamic driving style demands an equally dynamic recirculation of exhaust gases. This can be achieved with the use of a RDE-optimized turbocharger that reacts more quickly than conventional turbochargers.

With a combination of high- and low-pressure exhaust-gas recirculation, the air-flow management system becomes even more flexible. This means drivers can drive off at speed without a spike in emissions.

Equally important is the influence of temperature. To ensure optimum NOx conversion, the exhaust gases must be hotter than 200 degrees Celsius. In urban driving, vehicles frequently fail to reach this temperature. Bosch has therefore opted for a sophisticated thermal management system for the diesel engine.

This actively regulates the exhaust-gas temperature, thereby ensuring that the exhaust system stays hot enough to function within a stable temperature range and that emissions remain at a low level.

NOx emissions can now remain below the legally permitted level in all driving situations, irrespective of whether the vehicle is driven dynamically or slowly, in freezing conditions or in summer temperatures, on the freeway or in congested city traffic.

Bosch’s new diesel system is based on components that are already available in the market. It is available to customers effective immediately and can be incorporated into production projects.

At a press event in Stuttgart Bosch had dozens of journalists, from both Germany and abroad, drive test vehicles equipped with mobile measuring equipment in heavy city traffic, under especially challenging conditions. The results, shown in the chart below, show the performance of the Bosch technology against current and 2020 regulations.


AI can further boost performance. Even with the reported technological advance, the diesel engine has not yet reached its full development potential, Bosch said. Bosch now aims to use artificial intelligence to build on these latest advances.

This will mark another step toward a major landmark: the development of a combustion engine that—with the exception of CO2—has virtually no impact on the ambient air.

We firmly believe that the diesel engine will continue to play an important role in the options for future mobility. Until electromobility breaks through to the mass market, we will still need these highly efficient combustion engines.

—Volkmar Denner

Denner’s target for Bosch engineers is the development of a new generation of diesel and gasoline engines that produce no significant particulate or NOx emissions. Even at Stuttgart’s Neckartor, a notorious pollution black spot, he wants future combustion engines to be responsible for no more than one microgram of NOx per cubic meter of ambient air—the equivalent of one-fortieth, or 2.5%, of today’s limit of 40 micrograms per cubic meter.

Bosch calls for renewed focus on CO2 and well-to-wheels evaluations. Denner also called for a renewed focus on CO2 emissions. Denner said that consumption tests should no longer be conducted in the lab but rather under real driving conditions. This would create a system comparable to the one used for measuring emissions.

Moreover, he added, any assessment of CO2 emissions should extend significantly further than the fuel tank or the battery—a full well-to-wheels lifecycle approach.

We need a transparent assessment of the overall CO2 emissions produced by road traffic, including not only the emissions of the vehicles themselves but also the emissions caused by the production of the fuel or electricity used to power them.

—Volkmar Denner

He added that a more inclusive CO2 footprint would provide drivers of electric vehicles with a more realistic picture of the impact of this form of mobility on the climate. At the same time, the use of non-fossil fuels could further improve the CO2 footprint of combustion engines.



Albeit that the results from Bosch might seem impressive, there is really no new technology involved here; just a consequent optimisation and the use of available state-of-the-art technology. Having said that, we know that there is new technology in the pipeline that will bring further improvements.

We should also note that the level of 80-90% (or >90%) reported by Bosch is no better than the last results by others (e.g. ADAC and ams-magazine) on Euro 6d-TEMP cars and even the latest (and best) Euro 6c and Euro 6b cars. I also receive similar information from other on-going projects that have so far not been published.

One could conclude that diesel cars now are very clean in all respects, not only do they have lower CO, HC, PM/PN and unregulated emissions components that pose health hazard than gasoline cars; but now diesel cars also have similar low NOx as gasoline cars do have. In addition, diesel cars still have a substantial CO2 advantage over gasoline cars. Now we can just hope that legislators and the public become aware of these facts. It is time to re-evaluate the diesel car.


Good news for European car manufacturers if this is real.
It is unusual to hear statements like, they have "solved the NOX problem."

How much extra will this cost?
When will it be available on new cars?
Will it be retrofittable ?
Can they fit the necessary hardware soon, even if the software takes longer?
How reliable will it be?


Put this on the 300,000 VW diesels they bought back in the U.S.


It depends on what we compare to. There are several cars already on the market with this hardware but I cannot assess the level of software optimization on those cars. There is would be no additional hardware cost on those cars; only the cost for software development. Several of the newest production cars have NOx levels on the similar level as Bosch showed, so you could make your own assessment as to how much of this technology they use. BMW has shown similar NOx levels w/o LP-EGR but with a NOx storage catalyst instead and SCR, as in the Bosch case. With all mentioned hardware combined, there would be an option for further improvement.

All hardware has been available and in production since about 2016 (earlier for most components).

Retrofit? Yes, in theory, but car manufacturers prefer to sell new cars and if these fulfil (previous legislation), why would the manufacturer make the effort. Software updates are more likely and could be handled during normal maintenance. VW would not risk confidence and customer satisfaction by trying to retrofit the cars they bought back. They will most likely be scrapped.

Many cars certified according to Euro 6d-TEMP from September 1 last year and all models to be introduced after September 1 this year will most likely have some, or all, of this hardware.

Reliability of single components have been proven since several years; for the whole concept, I would say that we would have heard about significant reliability problems if there would have been any in the last two 2 years. Anyhow, radical change (if any) of software control (e.g. rate of EGR) under extreme ambient conditions must be demonstrated in field tests prior to production.


Ideally there would not be the need to continue building diesels, or ICEVs for that matter. However, clean cars are not at the right cost point yet, so we must suffer longer as the car companies string out the transition to meet their profit numbers.


Building clean(er) ICE cars that cost much less and use less rare elements than EVs is a really good idea.


I found the complete paper from Bosch. Usually, the conference organizer asks a fortune for the whole package of conference proceedings.


Here is a better report on it.
They say it will take 2 years to get into cars.
However, it looks like various companies are fixing it bit by bit anyhow, but this demonstrates how far they could go.

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