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Spark ignition engines are shown to have difficulty starting on high methanol-content fuels not only because of low fuel volatility but also because of electrical shorting of the ignition by methanol on the spark plugs. Using a concerted approach in which the fuel and ignition systems are optimized for fuel methanol, we have cold started a 2.5L spark ignition engine with port fuel injection down to -29°C on a 10.5 psi Reid vapor pressure M-85 (85% methanol, 15% gasoline). To minimize the amount of spark plug wetting, an exponential decay fuel algorithm is used which quickly generates flammable vapor mixtures while limiting the cylinder wetting. To overcome the spark plug wetting which does occur, ignition systems are used which have peak delivered currents twice as high as present-day automotive inductive ignitions.

Air-assist fuel sprays have been investigated experimentally with exciplex laser-induced fluorescence visualization and computationally with the KIVA-3 code. The exciplex-fluorescence technique provided simultaneous but distinct cross-sectional images of the liquid and vapor fuel distributions under simulated light-load conditions in both an atmospheric-pressure test rig and in a motored two-stroke engine. The computations resolved the flow through the injector passages upstream of and around the poppet, and included the effects of aerodynamic drop breakup, drop collisions and vaporization. Both the measurements and the calculations show that the fuel initially emerges from the injector as a hollow-cone jet. This two-phase jet collapses downstream as entrainment of air produces a low-pressure region beneath the poppet.

A quick and repeatable test procedure has been developed to investigate cold-start spark plug fouling using a single-cylinder test facility which is capable of quickly cooling the engine back to the test temperature. With a constant engine speed of 140 rpm, the fuel flow is controlled for a 5 minute start/idle period, followed by a 5 minute cool-down period with the fuel off. This facility dramatically reduces the cold-soak period of a cold start which would otherwise require hours. Under conditions where carbon fouling occurs, the effects of fuel calibration, fuel properties (aromaticity, vapor pressure, and surfactant additives), and spark properties (energy and gap size) on the number of cold starts, the spark waveforms, and the electrical-shorting mode were investigated. Fuel calibration had the strongest influence. The relative roles of soot and water and of different soot formation mechanisms are discussed.