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Westport/Isuzu CNG-DI Cleaner than Diesel, More Efficient than CNG

November 2, 2004

Isuzu and Westport recently entered into a new joint venture agreement through which Isuzu will provide Westport approximately $1 million for the design and construction of two next-generation CNG-DI ELF trucks to be delivered in 2005, according to the Green Car Congress. A technical analysis presented by Isuzu at the 9th International Association for Natural Gas Vehicles Conference shows that the mono-fuel CNG-DI engines can be 75 percent cleaner than today’s diesel engines and 25-30 percent more energy-efficient than current natural gas engines. The conventional use of CNG as fuel makes it possible to achieve virtually zero particulate matter (PM) emissions, with a significant reduction in NOx emissions as well. When it comes to the thermal efficiency, however, conventional CNG-powered engines are on par with gasoline-powered engines and slightly less efficient than conventional diesels. Isuzu and Westport wanted to improve thermal efficiency by 25 percent or more over the conventional approach and to achieve at least 75 percent lower emissions than the current ultra-low-emission vehicles. The CNG-DI system promises to be simple, lightweight, low-cost, reliable, and durable. It also has lower noise and less vibration. Isuzu has concluded that a good potential exists for commercial application of this technology. Isuzu and Westport first showed the CNG-DI technology in a 2-ton ELF prototype truck brought to last year’s Challenge Bibendum. The truck won 2 Gold and 1 Silver awards there. The CNG-DI engine in the ELF prototype used a 4.5-liter, in-line four-cylinder engine as the base. Isuzu developed the turbocharger Exhaust Gas Recirculation (EGR) oxidizing catalytic converter and urea SCR catalyst for NOx reduction. Westport and Isuzu jointly developed the electronically controlled common rail injection system and hot-surface ignition system. Isuzu/Westport CNG-DI ELF specifications include:
  • Displacement: 4.5 liter
  • Engine configuration: In-line, 4-cylinder
  • Power: 100 kW (134 hp)
  • Torque: 500 Nm (369 lb-ft)
  • Fuel storage: 2-bottle CNG cylinders (Dynetek)
  • Storage pressure: 250 bar (3,675 psi)
  • Maximum speed: 130 km/h (81 mph)
  • Operational range: 300 km (186 miles) Funding from the New Energy and Industrial Technology Development Organization (NEDO of Japan) and the Japan Gas Association supported the Isuzu/Westport research.
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    Exhaust Gas Recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique that is used in petrol/gasoline and diesel engines.

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