Research on alternative fuels like LPG has shown the marked difference against its counterpart gasoline
fuels due to its fast burning characteristics and combustion stability. Monitoring of combustion process is
inevitable as it forms the basis for vibration and noise characteristics of the engine. Conventional methods
of combustion monitoring with the help of intrusive in-cylinder pressure sensor is suitable for analyzing the
combustion process in the laboratory on test cell and may not be viable for the onboard diagnostics during
vehicle motion. The main objective of the current work is to measure the vibration and noise data and
correlate them to the LPG fueled engine combustion process to find the feasibility of devising a non-intrusive
diagnostic technique. Hence, along with the in-cylinder pressure, the noise and vibration data are acquired
simultaneously at different locations for different operating conditions and the critical orders are identified
with and without fuel running the engine through order tracking.