15/10/2025
🔹 Title: Shaft and Valve Synchronization (Engine Adjustment or Cycle)
🧩 Major components observed:
Camshaft (central, at bottom of swings):
It's the shaft that controls the opening and closing of the valves.
Spins at half the speed of the stork (1 lap of the tree = 2 laps of the stork, or 720°).
Swings (top of tree):
It's the levers that transmit the movement of the levers to the valves.
Each lever pushes a swing, opening the corresponding valve.
Valves:
IN (Intake) = Intake Valve (allow air/fuel mixture to enter).
EX (Exhaust) = Exhaust Valve (let the burned out gases out).
Stork (lower right, with hand):
It's the axle that turns the linear movement of the piston into rotation.
In the picture, the hand makes it rotate 360° (a full turn).
Turn Direction and Force (F):
Arrow F → indicates the sense of the rotation of the crankshaft and, therefore, the advancement of the engine cycle.
⚙️ What does the image show step by step:
🅰️ Top part — Starting position
Valves marked with IN and EX indicate which ones are open.
The camshaft is in a starting position where:
Some intake valves are opening.
Other exhaust valves going off.
This typically occurs during the valve crossing phase (when the piston is between exhaust and intake).
🔸 Valve crossing occurs when both valves (intake and exhaust) are slightly open at the same time, which improves the efficiency of filling the cylinder with fresh mix.
°️ Motion — 360° Spin
Hand spins the stork one full spin (360°).
The camshaft, when synchronized with a 2:1 ratio, rotates 180°.
This completely changes the position of the levers → and therefore, the valves that were open will now be closed, and vice versa.
💡 Each 360° of the crankshaft (one lap) equals half a cycle of the engine, as a full cycle requires 720° (two crankshaft laps).
🅲 Bottom — Opposite position
After turning 360°, you notice that:
Valves that were open before are now closed.
The ones that were closed, now open.
This demonstrates the alternation of intake and exhaust times on the cylinders.
Also seen the typical working sequence of a 4-cylinder engine in line, where the cylinders work in opposite pairs:
Cylinder 1 and 4 in sync.
Cylinder 2 and 3 in sync, but unphased 180°.
🔄 Set operation explained:
Each valve opens and closes at precise moments coordinated with the crankshaft:
Engine timing. Intake valve. Exhaust valve. Piston movement
Admission Open Closed Piston Lower
Compression Close Piston Goes Up
Combustion (expansion) Close Close Piston Low
Exhaust Closed Open Piston Goes Up
In a 4-cylinder engine, while one cylinder is in intake, one can be in compression, one in combustion and the last in exhaust.
This way the balance and continuous flow of power is maintained.
agr Practical use of this diagram
This type of graph is used for:
Adjusting Valve Slackness (in engines with mechanical tackles).
Verify timing of the cam shaft to the stork (timing).
Diagnose improper opening faults, valve noise or loss of compression.
Calibrate the engine during maintenance (e.g. 0.20mm exhaust, 0.15mm intake according to the model).
🧠 Technical trivia
A common crankshaft spins at half the speed of the crankshaft thanks to the belt or timing chain.
If this synchronization is lost (by jumping teeth or loose chain), the engine may lose compression or damage valves and pistons.
In modern engines, systems like VVT (Variable Valve Timing) modify valve opening timing electronically for greater efficiency.
✅ In summary:
This image schemetically depicts the synchronized movement of the shaft and intake and exhaust valves on an internal combustion engine.
Each 360° turn of the crankshaft changes the position of the valves, showing alternating behavior between IN (inlet) and EX (exhaust).
After 720° (two full laps of the stork), the cycle repeats, completing the 4-stroke cycle.
