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Bore Stroke Ratio Formula:
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The Bore Stroke Ratio is a fundamental parameter in engine design that represents the relationship between the cylinder bore diameter and the piston stroke length. It provides insights into engine characteristics and performance potential.
The calculator uses the simple formula:
Where:
Explanation: The ratio indicates whether an engine is oversquare (ratio > 1), square (ratio = 1), or undersquare (ratio < 1), each with distinct performance characteristics.
Details: The bore stroke ratio significantly influences engine characteristics. Oversquare engines (high ratio) typically favor higher RPM operation and horsepower, while undersquare engines (low ratio) favor torque production at lower RPMs.
Tips: Enter bore and stroke measurements in inches. Both values must be positive numbers greater than zero for accurate calculation.
Q1: What is considered a good bore stroke ratio?
A: There's no single "good" ratio - it depends on application. High-performance engines often use oversquare designs (1.1-1.3), while diesel and torque-focused engines use undersquare designs (0.7-0.9).
Q2: How does bore stroke ratio affect engine performance?
A: Higher ratios allow for larger valves and better breathing at high RPM, favoring horsepower. Lower ratios provide better mechanical advantage and piston speed control, favoring torque.
Q3: Can I use millimeters instead of inches?
A: Yes, as long as both measurements use the same units, the ratio will be identical since it's unitless.
Q4: What's the typical range for bore stroke ratios?
A: Most production engines range from 0.7 to 1.3, with modern performance engines trending toward 1.0-1.2.
Q5: Does bore stroke ratio affect engine longevity?
A: Extremely oversquare designs may have higher piston speeds and wear rates, while extremely undersquare designs may have combustion chamber shape challenges. Moderate ratios typically offer best durability.