A comparative study on operating range and combustion characteristics of methanol/diesel dual direct injection engine with different methanol injection timings

•Operating ranges at different SOIMs are identified respectively.•Methanol/diesel dual direct injection strategy could simultaneously achieve high fuel economy and low emissions.•Systematic analysis of combustion characteristics under various methanol injection strategies.•Injecting methanol at − 60 °CA aTDC results in lower CO and HC emissions under high engine load and ESR conditions.