Evaluation of AIr-Fuel Ratio and Vehicular Emissions of Different Efi Petrol Vehicles in Lahore, Pakistan

This study investigates the impact of air fuel ratio on EFI based petrol vehicles emission by On-Board Diagnostics (OBD) in Lahore, Pakistan. Vehicular Emission tests like CO, HC, NO, SO2, and CO2were performed using advanced analyzers at authorized workshops. It was observed that whenever the sum of Long-Term Fuel Trim (LTFT) and Short-Term Fuel Trim (STFT) values and Carbon Monoxide (CO) emissions, with vehicles having LTFT + STFT values between -10 and +10 consistently passing emission tests. Euro V vehicles showed the lowest emissions (CO <100 ppm, negligible HC), Euro IV vehicles had moderate emissions (CO ≤300 ppm, HC ≤2000 ppm), while Euro II vehicles, especially older models, exhibited the highest (CO ≤12000 ppm, HC ≤6000 ppm). OBD scanners can serve as an efficient preliminary screening tool to streamline emission testing in regions with limited infrastructure.