Vehicle evaluation of neat methanol—compromises among exhaust emissions, fuel economy and driveability

Methanol was evaluated as an alternative fuel in vehicles with spark-ignited, internal-combustion engines. Acceptable driveability was achieved with a methanol-fuelled car equipped with electronic fuel injection (EFI) which was modified to provide proper air-fuel ratios for methanol. the target level for driveability was not achieved with a methanol-fuelled carburetted car modified to provide proper air-fuel ratios for and increased vaporization of methanol. With the EFI car, using the average equivalence ratio (Φa = 0·96) and spark timing designed for the production gasoline car, exhaust emissions and fuel economy with methanol fuelling were compared to those with gasoline. With methanol, compared with gasoline, 60 per cent lower NOx, 3·5 times higher unburned fuel emissions (UBF), and similar CO engine emissions were measured. the air pollution significance of the higher UBF emissions from methanol combustion is unknown because the UBF species (mainly methanol) are different from those from gasoline combustion. A catalytic converter decreased emissions of UBF and CO similarly for both fuels. Fuel economy with methanol—about half that of gasoline on a volume basis—was 7–10 per cent better on an energy basis than that with gasoline. With methanol fuelling, spark timing and Φa were varied from production values to obtain a more acceptable compromise among driveability, exhaust emissions and fuel economy. While fuelling with methanol at Φa = 0·96, using best power rather than production spark timing increased fuel economy 3 to 6 per cent without significantly affecting emissions and driveability. As Φa was leaned to 0·62 while maintaining best-power spark timing engine and tailpipe (after converter) CO emissions decreased, engine UBF emissions increased, NOx and tailpipe UBF emissions were not greatly affected, and driveability deteriorated. With best-power spark timing and the Φa for maximum economy (0·83), driveability was acceptable, and CO and NOx emissions met the 1977 standards. At Φa = 0·83, NOx emissions were reduced below the statutory standard (0·4 g/mile) by retarding spark timing; however, driveability and fuel economy deteriorated. Although the feasibility and benefits of operating vehicles with neat methanol have been demonstrated, not all problems of methanol fuelling (for example, cold start) were addressed. In addition, other alternatives such as obtaining hydrocarbon liquids from coal or using methanol as fuel for stationary powerplants must also be considered to obtain the most efficient utilization of energy resources.