"Politicians should not restrict our engineers' capability by favoring or disadvantaging a certain technology," asserted Dr. Rolf Bulander, chairman of Robert Bosch Mobility Solutions, at the company's 2017 Mobility Experience technology meeting in Boxberg, Germany. Speaking of the diesel engine as a core power source for passenger vehicles going forward beyond 2025, Dr. Bulander made a robust defense of diesel technology.

“What is amiss when Paris, Madrid, Athens and Mexico City decide to ban diesel vehicles from their streets from 2025?" Dr. Bulander asked. "In our view, this is ecologically misguided—or, at best, environmental protection from a blinkered perspective. Blinkered, if only, because such driving bans ignore diesel’s outstanding efficiency, which is still needed to limit global warming. But, also, blinkered because it underestimates the potential still latent in this technology.”

Bosch spends half its €7B ($8B) annual R&D budget on environmental protection and resource conservation. "We invest a lot in making all powertrains fit for the future,” Dr. Bulander explained. The Boxberg event took place prior to a widely publicized U.K. proposal to restrict sales of new non-electrified vehicles after 2040.

The major automotive regions will not be able to achieve their "very ambitious" CO₂ targets solely on the basis of electric vehicles, which will require continued improvement in combustion-engine emissions performance, he said. "We want to support automakers in their efforts to make nitrogen-oxide driving emissions from diesel vehicles lower than in the test bay,” Dr. Bulander added.

Talking later to Automotive Engineering, fellow board member Dr. Markus Heyn added: “Here in Europe the focus is on cars and we think that is too short-sighted. If you think about car emissions only and don’t include other sources of pollution then banning cars won’t help. It’s not a holistic approach and we think there are better ways of lowering emissions such as improving traffic flow. And, of course, not all urban emissions are created by cars."

Dr. Heyn noted that Bosch engineers are confident that a "10-15% improvement in CO₂ levels can be achieved in combustion engines," and that the company is also looking at other solutions including synthetic (syn) fuels, in cooperation with energy companies.

“It is a viable alternative for us, because electrification does not encompass all mobility segments such as long-haul trucks, ships or planes. If we want to achieve the Paris climate agreement we need to come up with more alternatives than just electrifying passenger cars,” Dr. Heyn said.

He suggested a future whereby ‘syn’ fuel would be gradually blended with conventional fuels, increasing the percentage as costs came down, “It would be best if all countries pursued these alternatives, which doesn’t mean we stop electrification but combine it with a solid approach to ‘syn’ fuels.”

While NOx is an issue for both diesel and direct injection downsized turbocharged petrol engines, Dr. Heyn is confident that available technologies like NOx storage catalysts and SCRs with Real World Driving Emissions (RDE) legislation will “over the course of time” solve the problem, as well as “developing engine concepts that produce less raw emissions.”

Assessing Real World Driving Emissions

RDE comes into force beginning September 2018. The new test protocols are designed to give consumers more realistic figures for both exhaust emissions and fuel consumption.

At the Bosch Mobility Experience 2017 Automotive Engineering had the opportunity to assess the RDE procedure ourselves. The test car was based on a current generation 2.0-L diesel VW Golf that had been downsized to 1.7-L by Bosch and fitted with its own 2000-bar solenoid injection system and an appropriately sized turbocharger. Power is rated at 110 kW (147 hp) and 300 N·m (221 lb·ft) compared to the standard 148 hp and 251 lb·ft. It was fitted with SCR and DPF filters as well as an additional ECU controller and high-and low-pressure EGR systems.

As a Bosch engineer explained, the challenge of measuring exhaust emissions on the fly are manifold: Weather, temperature, humidity and barometric pressure, as well as GPS reckoning to get the milligrams per kilometer. There’s also the issue of test equipment accuracy in the field differing from that used in the laboratory, complicated by constantly changing exhaust gas volumes.

To compensate for this NOx sensors are located at both engine out to gather raw emissions with a second way post-SCR treatment. “This means we have a wide range of values and from that we can extrapolate emission levels once we’re back at base,” an engineer explained.

Our test route around Boxberg covered 40 km (24.8 mi) with an altitude gain of approximately 1600 m/100 km (5249 ft/62.1 mi). It included towns but no autobahn. The blue square boxes on the scatter plot depict the emission figures we achieved during the drive; even the highest at 46 mg/km was slightly over half the EU6 limits of 80 mg/km while the best read only 28 mg/km.

So, does the new RDE test cycle work? On the evidence of a brief test under controlled conditions that answer would appear to be a cautious ‘yes. But it would also seem from the hesitancy displayed by some of the engineers that there is scope for improving the accuracy of the mobile test equipment.