Four-Stroke Engine Laboratory

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0° · Intake · intake 2% open · exhaust 2% open

Intake

Crank
Cam
Stroke

~40× slower than a 800 rpm idle

0° · IntakeSpeed

Watch all four strokes — to doLet it run: intake, compression, power, exhaust.
Jump to the power stroke — to doUse the “Power” stroke button.
Select the piston — to doClick it in the scene or in the Parts tab.
Explode the engine — to doUse the exploded-view button in the toolbar.

Stroke 1 of 4 · 0–180° crank

Intake stroke

The piston moves down and the intake valve is open, so fresh air and fuel are drawn into the cylinder — like pulling back a syringe plunger.

Valve overlap

Overlap — and round again

At the very top, for a moment both valves are slightly open. The last exhaust leaving helps pull in the new charge, and the cycle starts again.

Live state
Crank angle
Camshaft anglehalf crank speed
Piston
Intake valve
Exhaust valve
Spark
Cylinderconceptual
Pressureillustrative model

Dimensions, valve timing, spark timing and the pressure curve are illustrative teaching values, not data for any real engine. Gas colours and the combustion glow are a conceptual visualisation, and valve lift is drawn 1.5× real size so it is easy to see.