Effect of compression ratio on the performance and combustion of a biogas fuelled spark ignition engine

► Experiments were conducted on a biogas fuelled SI engine at various equivalence ratio and number of compression ratios. ► Improvement in brake power and brake thermal efficiency with increase in compression ratio. ► Lean misfire limit is extended with increase in compression ratio. ► Enhanced compression ratio decreases hydrocarbon and carbon monoxide emission level and increase in NO emission. ► The reduction in ignition delay and higher heat release rate with increase in compression ratio.