For Bosch diesel claim, technical details to come

Photo credit: REUTERS

Has Bosch really cracked the code and figured out how to take harmful diesel emissions off the table by simply tweaking the turbocharger and by closely controlling the temperature of the air entering the engine?

Bosch CEO Volkmar Denner on Wednesday claimed engineers have developed technology that reduces nitrogen oxides emissions to as low as 13 milligrams per kilometer, or roughly 21 milligrams per mile -- a level that would easily meet the toughest diesel regulations on the books in the U.S. and Europe well into the next decade.

On one hand, no supplier has more expertise with diesel fuel, engines and emissions systems than Bosch. If there is a formula to make a diesel run so clean that it's no longer an issue for environmental regulators, it would not surprise me if Bosch found it. Bosch has been developing fuel injection systems since at least the 1930s.

On the other, Bosch's software is at the heart of the sweeping diesel emissions violations that surfaced in Volkswagen vehicles and has spread to other automakers. Bosch's culpability in the mess isn't yet clear, but the company has set aside $1.5 billion to deal with potential fines.

Michael Krueger, chief engineer for Bosch diesel engines, told me company engineers outfitted a fleet of 22 Volkswagens with proprietary 1.7-liter diesel engines equipped with super-responsive turbochargers and modifications to the engine's exhaust gas recirculation system that keeps the temperature of air entering the engines at 392 degrees Fahrenheit.

Those vehicles were tested in real-world driving situations in Stuttgart. Emissions ranged from a low of 13 milligrams of NOx per kilometer to 40 milligrams per kilometer in spirited driving -- both levels well under current U.S. and European limits.

Krueger told me changes to the test vehicles included equipment that is standard-issue on today's diesel vehicles. The turbocharger, he said, has been made more responsive than those used today. It has a smaller, low-friction turbine wheel that spins up to speed extremely quickly. The diesel fuel injection system's pressure is 31,900 pounds per square inch.

The exhaust gas recirculation system has low- and high-pressure circuits and keeps the temperature of the air allowed into the engine at 392 degrees Fahrenheit. There are some changes to the engine's software, and the cars were fitted with a system that injects urea into the exhaust to transform NOx into water and nitrogen.

Bosch claim
Bosch claims that its new diesel technology meets the strictest EPA regulations for NOx emissions, ranging from a low of 13 mg per kilometer to 40 mg per kilometer, depending on driving style. Below is the EPAs Bin classifications for NOx emissions.
Bin NMOG+NOx mg/mi
Bin 70 70
Bin 50 50
Bin 30 30
Bin 20 20
Bin 0 0

Automakers and suppliers, diesel engine manufacturers and research entities such as the Oak Ridge National Laboratory have spent billions over the years working to develop technologies that clean up diesel exhaust emissions. On the surface -- and to me at least -- Bosch's solution sounds overly simple.

Big breakthroughs are still possible with internal combustion engines. Toyota has raised the thermal efficiency of many of its new engines to more than 40 percent. Nissan's variable compression turbo four solves a problem engineers have been working on for nearly a century.

I will be checking with experts in diesel emissions and engine manufacturers asking them to vet Bosch's latest claims. Now, the early word on the street is that Bosch has not released enough technical details for a credible independent assessment.

But on Thursday in Vienna, Bosch published a paper detailing how it tested the system. We don't usually post these papers here -- they can be pretty dry -- but this one looks interesting.

If you have a strong background in engines and emissions, please read the paper and leave a comment below with your thoughts on Bosch's claims.

You can reach Richard Truett at

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