.
S.No. | Four stroke engine |
Two stroke engine |
1.
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It has one power stroke for every two revolutions of the crankshaft.
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It has one power stroke for each revolution of the crankshaft.
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2.
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Heavy flywheel is required and engine runs unbalanced because turning
moment on the crankshaft is not even due to one power stroke for every two
revolutions of the crankshaft.
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Lighter flywheel is required and engine runs balanced because turning
moment is more even due to one power stroke for each revolution of the
crankshaft.
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3.
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Engine is heavy
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Engine is light
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4.
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Engine design is complicated due to valve mechanism.
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Engine design is simple due to absence of valve mechanism.
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5.
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More cost.
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Less cost than 4 stroke.
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6.
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Less mechanical efficiency due to more friction on many parts.
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More mechanical efficiency due to less friction on a few parts.
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7.
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More output due to full fresh charge intake and full burnt gases
exhaust.
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Less output due to mixing of fresh charge with the hot burnt gases.
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8.
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Engine runs cooler.
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Engine runs hotter.
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9.
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Engine is water cooled.
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Engine is air cooled.
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10.
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Less fuel consumption and complete burning of fuel.
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More fuel consumption and fresh charge is mixed with exhaust gases.
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11.
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Engine requires more space.
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Engine requires less space.
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12.
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Complicated lubricating system.
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Simple lubricating system.
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13.
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Less noise is created by engine.
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More noise is created by engine.
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14.
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Engine consists of inlet and exhaust valve.
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Engine consists of inlet and exhaust ports.
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15.
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More thermal efficiency.
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Less thermal efficiency.
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16.
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It consumes less lubricating oil.
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It consumes more lubricating oil.
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17.
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Less wear and tear of moving parts.
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More wear and tear of moving parts.
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18.
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Used in cars, buses, trucks etc.
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Used in mopeds, scooters, motorcycles etc.
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