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The use of compressed natural gas (CNG) as a fuel for small vehicles presents challenges associated with the vehicle cost, system packaging, and vehicle range. The University of Tennessee with primary support from the Saturn Corporation has adapted a Saturn SL1 to dedicated CNG operation with the objective being to do so with a minimal impact on the production of the base vehicle. The adapted vehicle meets the California ULEV emission values at low mileage, achieves a gasoline equivalent fuel economy of 21 km per liter (49 miles per gallon) at a steady speed of 90 km/hr (55 miles per hour), and has a range (at 90 km/hr) of over 400 km (240 miles) when fueled with an initial tank fill of 24.8 MPa (3,600 psig). As expected, wide-open throttle performance of the adapted vehicle was degraded from the gasoline baseline vehicle. The vehicle design features are compared with two similar pre-production vehicles that have been described in the literature.

Tests were conducted using an ASTM Aviation Supercharge CFR engine to determine whether high levels of fuel-bound nitrogen lead to increased nitric oxide emissions in a supercharge engine. Fuel nitrogen levels were formulated by doping several different fuels with pyridine. The results of the testing on this particular engine indicate that the effects of fuel nitrogen on nitric oxide emissions were so small that they were masked by the uncertainties associated with the experimental procedures used. Comparisons with the results from other researchers suggest that the results of this study are probably associated with stratification of the fuel-air mixture. It is recommended that additional tests be conducted to investigate the effects of fuel-air mixing on fuel nitrogen conversion. The purpose of this study was to determine how the nitrogen content of liquid fuels affects the nitric oxide emissions from a spark ignition engine. The study was motivated by concerns that future fuels may contain higher levels of nitrogen than the fuels they will replace - particularly if these future fuels are derived from coal or oil shales.