COMPARISON BETWEEN SI AND CI ENGINES (GENERAL COMPARISON):
COMPARISON BETWEEN SI AND CI ENGINES (MERITS AND DEMERITS):
Spark Ignition Engines (SI)
Merits: Otto cycle is employed in petrol engine. Otto cycle is more efficient for a given compression ratio.
Operating speed is more. Speed range is 3000 to 6000 rpm
Starting is easy, since cranking effort required is less
Merits: Initial cost and maintenance cost are less
Produces less noise.
Weight per unit power is less
Specific fuel consumption is more.
The fuel used is petrol. It is costlier than diesel. It is volatile and fire hazard is more
Compression Ignition Engines (CI)
Demerits: Diesel engines works on diesel cycle. Diesel cycle is less efficient than Otto cycle for a given compression ratio.
Operating speed is less. Speed range is400 to 3500 rpm.
Starting is difficult since more cranking effort is required.
Demerits: More initial and maintenance costs since the construction is heavy and sturdy.
Produces more noise.
Weight per unit power is more.
Specific fuel consumption is less
The fuel used is diesel. It is cheaper than petrol. It is less volatile and fire hazard is less.
• Heat Engine is a machine which converts heat energy supplied to it into mechanical work.
• Heat energy is supplied to the engine by burning the fuel.