Final answer:
Cranking a gasoline engine with a computer-controlled system involves a series of tightly controlled processes that include air-fuel mixture regulation, spark timing, and variable valve timing to ensure efficient combustion and minimize emissions.
Step-by-step explanation:
When cranking a gasoline engine that uses a computer-controlled engine management system, various processes occur simultaneously to ensure efficient combustion and minimize emissions. These systems regulate the air-fuel mixture, ignition timing, and often control variable valve timing to improve the engine's performance and efficiency.
The process begins with the intake stroke, during which air is mixed with fuel. During the compression stroke, this air-fuel mixture is rapidly compressed in a nearly adiabatic process. When the air-fuel mixture is ignited by a spark plug, this triggers a conversion of chemical potential energy into thermal energy, increasing the pressure within the cylinder.
The ensuing adiabatic expansion is the power stroke, delivering most of the power to the crankshaft. Unburnt hydrocarbons and nitrogen oxides can form during combustion, but catalytic converters along with fuel standards significantly reduce these emissions. Finally, the exhaust stroke expels the used gas to prepare for the next cycle of the four-stroke engine.