Performance Analysis of Four-Stroke Multi-Cylinder Petrol Engine Using Alternate Fuels

The progressive exhaustion of conventional fossil-fuel reserves, combined with increasingly stringent emission legislation under Euro 6 and Bharat Stage VI (BS-VI) norms, has created an urgent imperative to develop and validate alternative fuel pathways for spark-ignition (SI) engines. This paper presents a rigorous experimental investigation of the performance and emission characteristics of a four-stroke, four-cylinder water-cooled petrol engine fuelled with four configurations: neat gasoline (baseline), 10% ethanol–gasoline blend (E10), 20% ethanol–gasoline blend (E20), and a compressed natural gas (CNG) pilot blend. Dynamometer tests were conducted at 1500 rpm across four discrete load conditions (25%, 50%, 75%, and 100% of rated load). Measured performance parameters include Brake Thermal Efficiency (BTE), Brake Specific Fuel Consumption (BSFC), Mechanical Efficiency, and Volumetric Efficiency. Exhaust emission constituents—HC, CO, CO₂, and NOₓ—were quantified using a calibrated five-gas analyser in accordance with ISO 8178. The Morse test was used to determine Indicated Power independently for each cylinder. Results demonstrate that E20 achieves the highest BTE of 33.2% at full load, a 10.3% relative improvement over the petrol baseline (30.1%), with BSFC concurrently reduced from 275 g/kWh to 245 g/kWh. HC emissions decrease by 27.6% and CO by 31.6% with E20, while NOₓ rises marginally by 7.2%. CNG blend delivers the lowest CO (1.68% vol) and NOₓ (810 ppm) but at a volumetric efficiency penalty. Uncertainty analysis confirms BTE values within ±1.32% at 95% confidence. E20 is substantiated as a viable drop-in alternative fuel requiring no hardware modification, aligned with India’s EBP 2025 mandate.