Last week, I had the privilege of presenting our light-duty diesel engine’s latest performance and emissions results at the SAE High Efficiency IC Engine Symposium and SAE World Congress. It’s always an honor to share our work with automotive executives, analysts, academics and engineers. And, it’s even more meaningful when those same individuals realize the potential our engine has to revolutionize passenger and commercial vehicle transportation.

The Achates Power 2.25L light-duty engine has a stroke of 166.65 mm, a bore of 75.75 mm and a stroke-to-bore ratio of 2.2.

The focus of the two presentations was a detailed benchmark studycomparing our opposed-piston architecture to a next-generation diesel engine equipped with the most advanced technologies. This 2.8L, four-cylinder, four-stroke engine is part of a U.S. Department of Energy (DOE)-funded project that is being developed to show the potential of meeting upcoming emissions regulations. The goal of the DOE project is to develop the engine to meet emissions levels within reach of Tier 3 or LEV III emissions regulations. By 2025, these standards will require OEMs to have a fleet average emissions level of 0.030 g/mi NMOG+NOx (non-methane organic gas+nitrogen oxide) for all light-duty vehicles below 8,500 lbs. gross vehicle weight. When comparing our engine design to the DOE-funded engine, we successfully demonstrated:

    • A 30% fuel economy improvement without hybridization or other costly vehicle enhancements
The Achates Power engine has an extremely flat brake-specific fuel consumption (BSFC) map, illustrating that its high efficiency also extends to low loads.
      This improvement—which is the average of both LA-4 (city) and highway driving cycles—is even more significant than what Achates Power has already shown for medium- and heavy-duty applications. The reason: the lower the speed and load operating modes (characteristic of light-duty applications) and the lower the engine-out NOx (required to achieve Tier 3 emissions standards), the greater the fuel efficiency advantage delivered by our opposed-piston engine.

    • The potential to meet the fully phased-in Tier 3 standards

In addition to a significant fuel economy gain, the Achates Power engine also demonstrated improvements in NOx and Soot. The NOx, particulate matter (PM) and hydrocarbon (HC) levels achieved with the Achates Power architecture meet the engine-out targets that the DOE project team estimated would allow the vehicle to attain the fully phased-in Tier 3 emissions with the appropriate aftertreatment. In the LA-4 driving cycle, the Achates Power opposed-piston engine produced NOx levels of 0.47 g/mi while the benchmark engine produced 0.82 g/mi. In the highway driving cycle, the gap between the two increased—0.34 g/mi of NOx for the Achates Power engine and 0.94 g/mi of NOx for the DOE-funded engine.

The Achates Power cycle average is based on a 10-mode weighted calculation, the same calculation used to predict the cycle fuel economy and emissions results of the DOE-funded engine. Achates Power is only measuring soot with an AVL415S smoke meter and not total PM, but close correlation was established and is presented in the technical paper.
    • Exceptional exhaust temperature management for catalyst light-off

As described in an earlier blog, the Achates Power opposed-piston engine features a patent-pending temperature control strategy for reaching higher exhaust temperatures during catalyst light-off than are possible with conventional, four-stroke diesel engines. This is especially important since more than 50% of the tailpipe emissions in an FTP-75 test are produced in the first 200 seconds of operation after a cold start with a conventional diesel engine.

    • Excellent vibration characteristics

Noise, vibration and harshness (NVH) are critical for any application, but they are especially important to light-duty vehicles like the one studied. The magnitude of the Achates Power engine’s vibration forces—the focus of a future blog post—are significantly lower than those of a modern, four-stroke gasoline V6 engine. Since the DOE-funded four-cylinder diesel engine would not provide a useful comparison (as the balance shafts effectively cancel all forces and moments internally), we benchmarked our design against the award-winning Honda 3.5L SOHC 60° V6. While the vibration moments of our engine are not perfectly balanced, they are several orders of magnitude below Honda’s design.

    • Seamless integration into existing vehicles

The Achates Power engine was evaluated for packaging into a light-duty pickup truck. Despite having different dimensions than the benchmark, there are no packaging concerns nor are vehicle modifications required. This study clearly demonstrates that the final CAFE 2025 light-truck fuel economy regulation has the potential to be met, and exceeded, by simply applying Achates Power technology. Using our opposed-piston engine, OEMs can comply with the regulations—and they can do so without additional investment in other vehicle technologies. With a game-changing solution like ours—one that meets the toughest global emissions standards, delivers significant fuel savings, fits into existing vehicles and delivers a smooth ride—OEMs have a clear path forward, and one that does not add cost compared to a conventional light-duty diesel engine. I’m sure you cannot wait to learn which companies will introduce our opposed-piston engine to their fleets first. Stay tuned to this blog and we will continue to highlight our customers’ announcements as they make them. For a short summary of the SAE World Congress paper, click here. You can also find the complete technical paper on the SAE website.

Clean Diesel Engine Emissions Engine Design Fuel Efficiency Standards

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