The objective of research is investigated the suitable ethanol combustion characteristic of partially premixed combustion (PPC) in a compression ignition (CI) engine. The first part investigates effects of start of fuel injection timing (SOI) on combustion, emissions and efficiency. Results was carried out at full load with single fuel injection on high compression ratio (CR) 28. Results have shown that ethanol combustion characteristics is intensified and a prolonged ignition delay promotes in higher fraction of premixed controlled combustion phase than decreasingly late combustion phase as well as early SOI. The compromise operating condition is suitable at 11 CAD BTDC. The second part investigates effects of engine operating parameters on combustion, emissions and efficiency. Results was carried out at half load with single fuel injection on CR18. The various SOI effect, results have shown that combustion characteristics are increase intensified level as well as early SOI. But SOI early more than suitable range SOI, these combustion are no significant. The various SOI is too long mixing duration similar to HCCI combustion, which is suitable at 128 CAD BTDC to acceptable in high efficiency and less emission. Due to mixing duration is a proper to perform worthiness ignition. But the stratified mixture are still close to stoichiometric ratio, which promotes reaction to ignite. The various EGR ratio effect, results have shown that combustion characteristics are increase intensified level as well as increase EGR ratio. EGR ratio less than 45% is uncontrolled operating condition. The shortage of oxygen in EGR ratio 61% that mixture is over stoichiometric ratio to very rich. According to the results, it can be concluded that suitable EGR ratio is 45% with lean mixture. The various fuel injection pressure effect, results have shown that combustion characteristics are increase intensified level as well as increase fuel injection pressure. So compromise ethanol combustion were carried out clearly improving efficiency and less emission better than diesel combustion.