Why does the engine speed increase as soon as the car steps on the accelerator? What is the principle?

After stepping on the accelerator, the throttle opening will increase, and the increase of throttle opening will increase the air flow into the air intake. At this time, the combustion heat release of the combustible mixture will also increase, thus increasing the work done by the gas on the piston and increasing the engine speed.

Extended data

Throttle, also known as "throttle" and "throttle". Refers to the control device that controls the engine power (thrust). On the piston aero-engine, the throttle valve controls the opening of the carburetor to control the filling amount of the cylinder, thus determining the output power of the engine. On the gas turbine engine, the throttle valve controls the metered fuel flow of the fuel regulator, thus determining the thrust generated by the engine. The position of the throttle is controlled by the driver operating the throttle lever in the cockpit, and it is transmitted to the carburetor or fuel regulator on the engine through control system components such as pull rod, rocker arm, torsion tube, steel cable, pulley and sector wheel. On an airplane, the throttle lever is always pushed forward to increase power (thrust) and pulled back to decrease power (thrust).