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For better power output and fuel economy of a four stroke cycle ignition engine, the ignition timing should preferably be set to the minimum spark advance for best torque (MBT). It is found that when the ignition timing is set MBT, the crank angle of the maximum combustion pressure (θpmax) usually lies between 12 and 14 deg after top dead center (ATDC) regardless of any engine specifications or operating factors. Therefore, the ignition timing can be controlled to be MBT by using the θpmax. This paper describes the relationship between the θpmax and MBT by both experimental results and numerical calculations, and MBT control system utilizing θpmax. And the test results by using this system are also described.

Pre-ignition phenomena of methanol fuel (M85) and unleaded premium gasoline were studied with use of the post-ignition technique. The combustion pressure as well as a signal from the pre-ignition detector were analyzed. It was found that methanol fuel is more susceptible to pre-ignition compared to gasoline fuel. Large cycle-by-cycle variations are present with combustion by surface ignition at the time of pre-ignition. This was caused by wide variations in the 0% mass fraction burned point. Since ionization signals from the pre-ignition detector prior to spark ignition indicate the 0% mass fraction burned point by surface ignition, prediction of pre-ignition is possible with use of the post-ignition technique. Platinum tipped spark plugs were found to be highly susceptible to pre-ignition with methanol fuel.