Understanding Stroke
* Stroke is the distance that the piston travels from its highest point (top dead center, TDC) to its lowest point (bottom dead center, BDC) in a single cycle.
* It's one of the key dimensions that determine an engine's displacement (volume of air/fuel mixture an engine can displace in a single cycle).
Methods to Measure Stroke
1. Direct Measurement:
* Using a ruler: If you have access to the engine's crankshaft, you can directly measure the distance between the two extreme positions of the crankpin, which is essentially the stroke.
* Using a dial indicator: This is a more precise method. Mount the dial indicator on the engine block so its stylus contacts the piston crown. Rotate the crankshaft by 180 degrees (one full stroke) and note the difference in the dial indicator readings.
2. Using Engine Specifications:
* Service manuals and technical specifications: These resources will typically list the engine's stroke.
* Online databases: Websites like EngineLabs or manufacturer websites often provide detailed engine specifications, including stroke.
Important Considerations:
* Engine type: The method you choose will depend on the engine type. Accessing the crankshaft might be easier on some engines than others.
* Safety: Always follow proper safety procedures when working on engines.
* Accuracy: For the most accurate measurement, consult official sources and use precise tools.
Example:
Let's say you measure the distance between the two extreme positions of the crankpin to be 90 millimeters. This would indicate a stroke of 90 millimeters.
Formula for Engine Displacement:
Once you know the stroke, you can calculate the engine's displacement using this formula:
* Displacement = π * (bore/2)² * stroke * number of cylinders
Where:
* π = 3.14159
* bore = diameter of the cylinder
* stroke = the distance the piston travels from TDC to BDC
* number of cylinders = the number of cylinders in the engine
By understanding stroke, you can gain insights into an engine's performance characteristics, such as its torque output and power delivery.
