Mazda Recognized for Breakthrough in Diesel Particulate Filter Combustion Analysis - Holds Promise to Recover Fuel Economy Lost to Cleaner Emissions
By: Mike Levine Posted: 04-23-08 23:27 PT
© 2008

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We may be driving the cleanest burning heavy duty (HD) diesel pickups ever built but one of the most common complaints since the beginning of last year is their poor observed fuel economy, versus earlier diesel trucks. Repeat buyers are reporting negative differences of up to 3 miles-per-gallon. And earlier this month our road tested F-450 achieved only 9.5-mpg.

It's difficult to quantify how much the average fuel economy has decreased in HD pickups, because three-quarter-ton and up trucks aren't required to display EPA mileage figures on their window stickers, like half-ton trucks.

The reason for the mileage drop is new emissions hardware necessary to meet the U.S. federal government's strict Tier 2 Bin 5 regulations. The standards went into effect on January 1, 2007. They call for a ten-fold reduction in soot and two-fold cut in nitrogen oxide (NOx) over the previous regulations.

Focusing on the soot side of the clean diesel equation, new oil burning HD pickups from Chrysler, Ford and General Motors use a diesel particulate filter (DPF) to trap engine soot before it can leave the tailpipe (see picture at top). But these filters slowly fill up, restricting exhaust flow. A process called 'regeneration' is used to incinerate the soot - cleaning out the particulate trap for another cycle. During regeneration the engine injects metered amounts of diesel fuel into the DPF to temporarily spike the temperatures high enough to burn off all the soot. In the case of GM's Duramax 6.6-liter V8 diesel, that engine uses up to 6/10 of a gallon of fuel to regenerate the DPF. Depending on a truck's duty cycle, regeneration can happen as often as every 250 to 300 miles. Hence the drop in fuel economy.

There are other reasons for the drop in economy, like a change in diesel's composition. Oil companies have to produce ultra low sulfur diesel (ULSD / 15 parts-per-million sulfur) that won't gum up DPFs like the old low sulfur diesel (LSD / 500 parts-per-million sulfur) would. ULSD has slightly less energy content per gallon versus LSD. But these fuel economy losses are marginal compared to the mileage lost to DPFs.

Mazda Motor Corporation has been taking a close look at catalytic materials used in regeneration, with the goal of reducing the time needed for the process to cut fuel consumption. Catalytic materials help speed up or enable chemical reactions (think catalytic converter). As an added bonus, CO2 emissions could also be lowered. This analysis effort, documented in a technical paper written by Mazda engineers, has been recognized by the Society of Automotive Engineers of Japan.

While all heavy duty pickups stand to gain in fuel economy from this new analytical approach, it could be Ford's Super Duty that gains the most first. Ford owns 33% of Mazda. Perhaps it's already being used to help design the DPF for Ford's upcoming 4.4-liter V8 diesel, or the next generation Power Stroke V8 that will replace the current 6.4-liter built by Navistar.

Mazda's Press Release is Below:

Hiroshima, Japan - Mazda Motor Corporation has announced that it received the Outstanding Technical Paper Award at the 58th annual Society of Automotive Engineers of Japan awards presentation for its analysis of the combustion mechanism of catalysts in diesel particulate filters.

Mazda has been conducting research into combustion mechanisms to eliminate particulate matter, mainly soot, from diesel engine exhaust emissions. The Hiroshima-based company developed an original analytical method which demonstrated that the oxygen exchange characteristics of catalysts play an important role in accelerating the combustion of particulate matter. This work will aid development of highly efficient diesel particulate filters (DPF) in the future. Additionally, the newly developed analytical method can be applied not only to automobile diesel engines, but also to general purpose diesel engines. The award recognizes these achievements, which provide tangible development guidelines for a wide range of future diesel engine technologies.

Diesel engines are popular mainly in Europe because they have better fuel economy than gasoline engines and produce fewer CO2 emissions, which are commonly regarded as a major cause of global warming. However, a treatment process (combustion) is necessary to remove the particulate matter (soot) that is produced in the exhaust. To promote combustion of the particulate matter, the exhaust gases must be heated sufficiently. This requires extra fuel and is one of the causes of impaired fuel economy.

Mazda will leverage its new analytical method to find ways of accelerating particulate matter combustion in order to significantly reduce exhaust processing times. By developing this technology, Mazda intends to cut fuel consumption and achieve cleaner exhaust emissions with less CO2.

The Society of Automotive Engineers of Japan has conducted an awards program since 1951 as a means of encouraging the advancement of automotive engineering and technologies. Its Outstanding Technical Paper Award recognizes individuals and their collaborators for outstanding research in the field of automotive technology.

About the Outstanding Technical Paper Award

Awarded for:
“Study on low temperature oxidation of diesel particulate matters by oxygen storage component for the catalyzed diesel particulate filter”

Kenji Suzuki, Technical Research Center, Mazda Motor Corporation

Kouichiro Harada, Technical Research Center, Mazda Motor Corporation
Hiroshi Yamada, Technical Research Center, Mazda Motor Corporation
Kenji Okamo, Technical Research Center, Mazda Motor Corporation
Akihide Takami, Technical Research Center, Mazda Motor Corporation

The Society of Automotive Engineers of Japan confers six awards each spring, namely: the Asahara Science Award, the Asahara Award of Merit in Technology, the Outstanding Technical Paper Award, the Technological Development Award, the Scientific Contribution Award and the Technological Contribution Award. The award ceremony is due to take place during the society’s spring conference at the Pacifico Yokohama Convention Center on May 22, 2008.

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