010-180°
Intake
The piston drops and the intake valve opens. The growing space draws in air, with fuel mixed into it.
See inside a working engine.
A four-cylinder engine you can turn in your hands. Watch the pistons, valves and crankshaft run through the four-stroke cycle while coolant, oil and air move through the systems around them. Click any part to find out what it does.
Inline-41-3-4-24-stroke · 720°8 · 2 per cylinder
Systems
Inline-four teaching model
Spin the engine, scroll to zoom, and click any part in the view to read what it does. Or pick one from the systems list.
- Layout
- Inline-4
- Firing order
- 1-3-4-2
- Cycle
- 4-stroke · 720°
- Valves
- 8 · 2 per cylinder
Loading the engine…
Focus
Cycle position
0°
IntakeCompressionPowerExhaust
Intake · cylinder 1
Firing12341-3-4-2
Plug into the car
Read the engine that is actually in front of you. An ELM327 OBD-II adapter talks to the diagnostic port under the dashboard; once it is connected, the 3D engine above follows your real revs while live sensor values stream in beside it.
OBD-II live link
Bluetooth or USB adapter
Bluetooth needs Chrome on Android, or Chrome or Edge on a computer. iPhone browsers cannot open a Bluetooth adapter — but the 3D explorer above works on iPhone as it is.
- 1 Plug an ELM327 adapter — Bluetooth or USB — into the OBD-II port under the dashboard, ignition on.
- 2 Connect, then allow the adapter when the browser asks. A Bluetooth adapter asks you to pick it from a list.
- 3 The car's own USB sockets only charge phones and carry audio — they carry no engine data.
Your car
Every car answers a request for its VIN — the identity code stamped into the body. Decode it and you get the car itself: make, model, year, and the exact engine, down to how many cylinders it has and how they are arranged.
Vehicle identity
Paste the 17-character VIN from the windscreen or door jamb — or connect an adapter in the live link panel and it is read from the car for you.
0/17
The four-stroke cycle
One complete cycle takes two full turns of the crankshaft — 720 degrees — and each of the four cylinders is somewhere different in it at any moment. That overlap is what keeps the engine turning smoothly.
02180-360°
Compression
Both valves shut and the rising piston squeezes the charge into a small space. Squeezing it is what makes the burn so forceful.
03360-540°
Power
The plug fires. Expanding gas slams the piston down and the rod turns the crankshaft. This is the only stroke that makes work.
04540-720°
Exhaust
The exhaust valve opens and the rising piston pushes the burnt gases out into the manifold.
Keep it serviced
Fault codes only appear once something has already gone wrong. The parts that wear out quietly — oil, filters, belts, brake fluid — are tracked by date and mileage instead.