The injection timing variation has a robust effect on emission formation in direct combustion diesel engine with thermal barrier coating. The piston head and cylinder were coated with Zirconium at 40 micron thickness. Low Heat Rejection (LHR) engine has high heat with standing capacity inside the combustion chamber, so the in-cylinder temperature is very high in part load and full load condition, which leads to increase the NOX emission. In the present investigation neat Jatropha oil methyl ester (JME) as well as the blends of varying proportions of Jatropha methyl ester and diesel were used to run a LHR-CI engine with standard injection timing and retarded injection timing. Significant improvements in engine performance and emission characteristics were observed for JME fuel. The addition of JME to diesel fuel has significantly reduced HC, CO emissions but it increases the NOX emission slightly with standard injection timing. The NOX emission was decreased with retarded injection timing with negligible effect on fuel consumption rate. Similar trend in brake thermal efficiency and exhaust gas temperature were observed with retarded injection timing, while maximum cylinder gas pressure and ignition delay were decreased.

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