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Before Top Dead Center (BTDC)
- Definition: BTDC refers to the position of the piston in an engine’s cylinder as it moves upward in its stroke, just before it reaches the highest point, known as Top Dead Center (TDC).
- Position: It occurs just before the piston reaches the top of its travel.
- Significance:
- This position is critical in the context of engine timing and operation.
- Timing events such as ignition or fuel injection are often referenced to positions like BTDC to ensure efficient combustion and engine performance.
- Usage:
- In spark-ignition engines, the ignition of the air-fuel mixture is often timed to occur slightly BTDC to allow complete combustion by the time the piston reaches TDC, maximizing power output.
- Valve timing, particularly the closing of the intake valve, may also be referenced to BTDC to optimize the engine’s volumetric efficiency.
- Application: Accurate identification and use of BTDC is essential for engine tuning, performance optimization, and ensuring smooth engine operation.
- Measurement: BTDC is typically measured in degrees of crankshaft rotation before the piston reaches TDC.