A Lean-Burn, Sub-Compact Natural Gas Vehicle 961676
This study evaluates a prototype, light-duty natural gas vehicle using lean-burn technology. Emissions and fuel economy for lean-burn operation are compared to that of stoichiometric operation. The vehicle is a sub-compact, 1991 Chevrolet Turbo Sprint. Multi-port natural gas injection was used to fuel the engine at a relative air/fuel ratio of 1 4.
The main analysis evaluates emissions and fuel economy of lean-burn operation using California Air Resources Board specified emission-testing fuel. Comparisons are made to stoichiometric natural gas and gasoline operation. As well, engine-out versus tail-pipe emissions are presented, along with a brief analysis of emission sensitivity to fuel composition.
Lean-burn results show a 33 3% improvement in fuel economy over Transport Canada's gasoline results and a 9 5% improvement over stoichiometric operation on natural gas. Emissions of CO and NMOG for lean-burn operation were encouraging however, Nox levels were over 30 times greater than for stoichiometric operation and 3 5 times higher than the U.S. Federal Tier 1 Nox limit.
Stoichiometric operation demonstrated the potential to meet ultra-low emission vehicle standards. As well fuel economy measured 21 7% higher than that measured by Transportation Canada on gasoline.