Experimental Studies on a Small-Bore Port Fuel Injected SI Engine Operated on Neat Methanol and Comparison with Gasoline

In many Asian countries a significant automobile market share is held by two and three wheelers. Generally, cost and simplicity considerations limit the performance and emission levels of small engines. Methanol is an excellent alternative fuel for SI engines due to its high-octane number, high flame speed, presence of oxygen in its molecule and thus can be used to enhance the performance of small engines. However, use of neat methanol in SI engines poses constraints due to low energy density and poor vaporization characteristics. Also, the effectiveness of methanol as a fuel has still to be thoroughly investigated in small-bore SI engines in order to assess its potential. In this work, a small-bore 200cc three-wheeler automotive engine was modified to operate in the port fuel injection mode with neat methanol as the fuel. Experimental studies on the engine were conducted initially at different loads at stoichiometric conditions and performance, combustion and emissions were compared with operation on gasoline under similar conditions. The effect of air fuel ratio was also studied with the two fuels in order to identify the prospects of operating the engine with lean mixtures. The engine showed improved brake thermal efficiency and lower CO2, THC, and NOx emissions with methanol as compared to gasoline. The combustion characteristics including cycle by cycle variations have also been compared. Detailed experimental results are presented and discussed in this paper.