Learn
Otto Cycle
The Otto Cycle is the thermodynamic cycle behind every petrol engine from motorcycles to cars to generators.
This interactive simulation lets you drag a crank angle slider through all four strokes intake, compression, power, and exhaust while watching the piston move and a PV diagram trace itself in real time.
Adjust the compression ratio from 4:1 to 14:1 and see how efficiency, peak pressure, and peak temperature change instantly. Every state point is calculated using actual isentropic relations (PVγ = constant) and constant volume heat addition.
Built for mechanical engineering students, GATE and interview prep, and anyone who wants to understand what happens inside an engine at one degree at a time.
Try this simulation yourself
Drag the crank angle slider slowly from 0° to 720° — watch the piston move and the dot trace the complete PV diagram in real time
Intake (0–180°) — piston drops, intake valve opens (blue), air-fuel mixture enters. Dot moves along the bottom of the PV diagram at constant pressure
Compression (180–360°) — both valves shut. Piston rises, gas gets squeezed. Watch pressure climb from 101 kPa to over 1800 kPa on the orange curve
Power (360–540°) — spark flashes at TDC. Pressure spikes vertically on the PV diagram (combustion). Then the red expansion curve pushes the piston all the way down. This is the work output
Exhaust (540–720°) — exhaust valve opens (purple), piston pushes burned gas out. Pressure drops back to atmospheric
Now drag the compression ratio slider — watch efficiency change from 42% at 4:1 to 65% at 14:1. The PV diagram stretches taller as peak pressure increases
The shaded area inside the PV cycle = net work output per cycle. Bigger area = more power per stroke