Environmental and economic factors are contributing to a new market for vehicular engines fueled by natural gas. Development of a state of the art electrically controlled natural gas fueled engine is detailed in this paper. The engine is a lean burn, turbocharger-intercooled engine controlled by a full authority electronic control system. This system controls fuel metering, spark timing, boost pressure, throttle valve and governing. The control system features closed-loop adaptive learn fuel control with feed back provided by a universal exhaust gas oxygen sensor. The development of the engine includes development of the control system and other engine component as well as substantial amount of steady state and transient control system calibration work. Reliability was also proven by both intensive bench tests and field operations. This R&D led to a final engine calibration which provides good efficiency and transient response while meeting Korea proposed ULEV and USA LEV emissions levels.