Criteria S.I. Engine (Petrol or Spark Ignition Engine) C.I. Engine (Diesel or Compression Ignition Engine) Working Cycle Works on Otto Cycle or Constant Volume Cycle. Works on Diesel Cycle. Mixture During Suction Stroke Takes a mixture of air and petrol during the suction stroke. Takes only air during the suction stroke. Fuel Used Uses petrol as fuel. Uses diesel as fuel. Compression Ratio Has a compression ratio that varies from 6 to 10. Has a compression ratio that varies from 16 to 20. Engine Weight and Cost S.I. engines are lighter and cheaper. C.I. engines are heavier and costlier. Initial Cost Initial cost is lower compared to C.I. engines. Initial cost is high due to high compression ratio. Starting Starting is easy. Starting is difficult, especially in cold conditions. ...
Internal Combustion Engines (IC) External Combustion Engines (EC) Combustion of fuel takes place inside the cylinder. Combustion of fuel takes place outside the cylinder. They are simple in nature. They are complex in nature. Initial cost is low. Initial cost is high. They have high thermal efficiency. They have low thermal efficiency. Less water is required for heat dissipation. More water is required for heat dissipation. Starting is easy. It takes time to start. These engines require less space. Require large space. Lower ratio of weight to power output. Higher ratio of weight to power output. Used in automobiles, aircraft, etc. Used for large-scale power generation, e.g., steam engines, steam turbin...