Isuzu will put $1.3 million into a one-year project aimed at a 25 percent improvement in fuel economy over current spark-ignited CNG engines. The CNG-DI technology offers ultra-low emissions and improved fuel economy.
CNG-DI uses late-cycle high-pressure injection of CNG into the combustion chamber in a similar fashion to the diesel cycle. Natural gas has a higher ignition temperature than diesel fuel, so a glow plug is used to achieve ignition. A CNG-DI injector is shown at right.
The Japanese government is supporting the move to CNG in vehicles as a substitute for diesel engines, in an effort to cut particulate and greenhouse gas emissions. The government is subsidizing both CNG vehicles and CNG fuel prices that are 54 percent less than gasoline and up to 38 percent less than diesel on an energy-equivalent basis. There are currently more than 24,000 natural gas vehicles in Japan.