The ignition delay of diesel without and with IJP operations, 40LFPO, 40LFPO10DMC and 40LFPO10DMC + IJP operations with brake power is depicted in Fig. 7. The duration measured in crank angle, between the beginning of injection and ignition of the fuel is called as the ignition delay. The ignition ability of a diesel engine is mainly influenced by the chemical and physical properties of the fuel [34]. It can be observed from the figure that the ignition delay decreases with the increase in the load which is due to the increase in the cylinder temperature. Generally, the ignition delay is decreased by fuel atomization, oxygen concentration, fuel quality and swirl motion, etc. inside the combustion chamber. The ignition delay of 40LFPO is longer compared to that of diesel, diesel + IJP, 40LFPO10DMC with and without internal jet piston, due to its lower cetane number and higher density. By inducing turbulence, the ignition delay of the diesel operation is marginally reduced throughout the load spectrum.