5.2 Gasoline engines The heat engine we now have in almost all of our motor vehicles are internal combustion engines Gasoline is vaporized and mixed with air to form a combustible mixture inside a closed chamber The mixture is compressed to about 6 to 10 times atmospheric pressure, then ignited with an electric spark On ignition, the fuel explodes, forming hot gases( co2, h2o, n.. The resulting hot gases(1000 oC) expand with great force against the piston, causing the crankshaft to rotate Figure 3.9 The four strokes of a four About 25 of the chemical energy in the spark-ignited internal combustion engine fuel can be converted to mechanical (a) compression, (b) combustion energy in a modern gasoline engine (c)exhaust, and(d) fuel-air intake5.2 Gasoline Engines Figure 3.9 The four strokes of a four spark-ignited internal combustion engine: (a) compression, (b) combustion, (c) exhaust, and (d) fuel-air intake. • The heat engine we now have in almost all of our motor vehicles are internal combustion engines. • Gasoline is vaporized and mixed with air to form a combustible mixture inside a closed chamber. • The mixture is compressed to about 6 to 10 times atmospheric pressure, then ignited with an electric spark. • On ignition, the fuel explodes, forming hot gases (CO2 , H2O, N2 …). • The resulting hot gases (1000 oC) expand with great force against the piston, causing the crankshaft to rotate. • About 25% of the chemical energy in the fuel can be converted to mechanical energy in a modern gasoline engine