A little more
understanding.
A little fuel. A precisely timed spark. Meet the remarkable choreography that turns combustion into movement. Inside a gasoline engine, controlled combustion pushes a piston. A clever linkage turns that back-and-forth motion into rotation. Drag the cutaway to look closer.
How it works
Inside a gasoline engine, controlled combustion pushes a piston. A clever linkage turns that back-and-forth motion into rotation. Drag the cutaway to look closer. Separate the engine, then select a component. Six simple ideas work together with extraordinary precision. Follow one cylinder through a complete cycle. Two crankshaft revolutions create one power stroke. Slow it down, pause, or choose a phase. Fuel stores chemical energy. Combustion raises gas pressure, which pushes the piston. The crankshaft and transmission carry that work to the wheels. At 3,000 revolutions per minute, a four-stroke cylinder completes 25 cycles each second. Most of the action is too fast to see.
Dive deeper
The geometry of reciprocating motion
The piston is constrained to a line while the crank pin follows a circle. With crank radius r, rod length l and crank angle θ measured from top dead center, piston displacement x follows the slider-crank relationship. The rod must be longer than the crank radius. The visualization uses this geometry rather than an independently animated piston.
x = r(1 − cos θ) + l − √(l² − r² sin² θ)Work, pressure, and the ideal Otto cycle
The net indicated work is the area enclosed by a pressure–volume loop. An ideal Otto cycle approximates compression and expansion as isentropic, with constant-volume heat addition and rejection. Real combustion has finite duration; heat transfer, pumping and friction reduce useful shaft work. This diagram illustrates timing and mechanism, not a calibrated thermodynamic simulation.
W = ∮ p dV · cycles/s = RPM ÷ 120What the cutaway simplifies
Valve opening is shown by stroke, ignition at top dead center, and one representative cylinder. Real engines open valves before or after these boundaries and usually initiate the spark before top dead center. The playback takes several seconds per cycle so you can inspect motion; it is not the displayed example operating RPM.
Interesting facts
4 — strokes per cycle. Intake, compression, power, exhaust.
720° — of crankshaft rotation. Two full revolutions for one cycle.
25 — cycles per second. Per cylinder at an illustrative 3,000 RPM.
Good questions.
Is this how every car engine works?
This is a simplified spark-ignition, four-stroke gasoline engine. Diesel engines ignite fuel through compression heating; electric vehicles use motors. Real engines may have multiple cylinders, variable valve timing, turbochargers and direct injection.
Why are there four strokes but only one power stroke?
The cylinder must first take in fresh charge and compress it. Combustion supplies the expansion stroke. A final stroke pushes exhaust out so the sequence can repeat. Rotational inertia and other cylinders help carry the crank through the remaining strokes.
Does the fuel explode instantly?
Normal spark-ignition combustion is a rapidly propagating flame, not an instantaneous detonation. The glow shown here indicates energy release; it does not model detailed flame chemistry.