FOUR-STROKE ENGINE Single-cylinder petrol cutaway. Slow motion, 7.5 rpm. CRANK ANGLE 0° CAM ANGLE 0° CYCLE 1 OF 2 STROKE 1 OF 4 INTAKE Piston moves down. The intake valve is open and fresh air-fuel mix flows in. The intake valve closes just after the bottom. The rising piston squeezes the charge. Hot gas expands and pushes the piston down. Only this stroke delivers power. The exhaust valve is open. The rising piston pushes burnt gas out. The camshaft turns at half crank speed: 360° of cam for 720° of crank. Each valve is pushed open by its cam lobe and closed by its spring. One power stroke every two crank turns. The flywheel carries the other three. Both valves are open together for only about 20°, at the end of exhaust and the start of intake. Valve and spark angles are typical values. Real engines vary. Geometry, flow and burn are simplified. 0° 180° 360° 540° SPARK IN EX ONE LAP = 720° CRANK = 360° CAM CRANK 2 : CAM 1 INTAKE CLOSES 45° AFTER BOTTOM SPARK 30° BEFORE TOP EXHAUST OPENS 45° BEFORE BOTTOM OVERLAP: BOTH OPEN, ONLY 20° INTAKE CLOSES 45° AFTER BOTTOM SPARK 30° BEFORE TOP EXHAUST OPENS 45° BEFORE BOTTOM OVERLAP: BOTH OPEN, ONLY 20° Fresh charge Compressed charge Flame front Burnt gas Dial arcs: valve open
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Seven and a half rpm, slow motion: one full cycle is two crank turns (720°) and the camshaft turns once. Valve and spark angles are typical values; real engines vary, and geometry, flow and burn are simplified.

What this page is: a repackaging, by the owner's assistant, of the finished animation files that an AI agent built (the same drawing, timing and engine code as the video), wrapped with a Play/Pause button and a time slider. The video on the main page is the reference. The player uses the fonts on your own device, so letter shapes differ slightly from the video.

Back to the page with the video, the build details and the prompts