Cold Starts Using M-85 (85% Methanol): Coping with Low Fuel Volatility and Spark Plug Wetting 910865
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.