4-Stroke Engine & Otto Cycle
Watch intake, compression, power and exhaust strokes with valves, spark and a pressure-volume diagram.
Press Play or drag the crank wheel round. Follow intake, compression, power and exhaust, and watch the pressure–volume loop being drawn.
About the 4-Stroke Engine & Otto Cycle
Free 4-stroke engine & otto cycle. Watch intake, compression, power and exhaust strokes with valves, spark and a pressure-volume diagram. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for engineering, the 4-stroke engine & otto cycle runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Watch intake, compression, power and exhaust strokes with valves, spark and a pressure-volume diagram. Use it to explore engineering ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the 4-Stroke Engine & Otto Cycle
- Use the controls to change Engine speed. The simulation reacts instantly.
- Press "Play / Pause", "Step 90°" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Step through the strokes one at a time.
- Drag the crank wheel by hand.
- Watch when the valves open and the spark fires.
Key ideas you can learn
- Four strokes make one cycle: intake, compression, power, exhaust.
- The crankshaft turns twice for each cycle.
- Only the power stroke makes work.
- The area inside the P–V loop is the work per cycle.
Where this is used in the real world
Cars, motorbikes, lawnmowers and generators use four-stroke engines.
Who is this simulation for?
Engineering and technology students, makers, robotics clubs and teachers of design and technology. It gives a hands-on feel for how machines behave before you build a real one.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What are the four strokes?
Intake, compression, power and exhaust.
Why does the crankshaft turn twice per cycle?
Each stroke is one up or down motion of the piston, half a turn, and there are four strokes.
Is the 4-Stroke Engine & Otto Cycle free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the 4-Stroke Engine & Otto Cycle work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.