In a 4-stroke engine, exhaust gas is expelled in a pulsating manner, determined by the exhaust valve's opening and the engine's speed, which can create a continuous flow at higher speeds. Each exhaust valve event generates a pressure wave, and with multiple cylinders, these pulses occur at different timings, normalizing into a more constant flow by the time they exit the exhaust system. The relationship between engine rotations and wheel rotations is direct but complex, influenced by gear ratios in the transmission and final drive. Overdrive gears allow for multiple wheel rotations per engine rotation, optimizing speed without excessive engine strain. Understanding these dynamics is crucial for evaluating engine performance and efficiency, as detailed in engineering texts on internal combustion engines.