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Bore to Stroke Ratio Formula:
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The Bore to Stroke Ratio (BSR) is a fundamental parameter in engine design that compares the cylinder bore diameter to the piston stroke length. It helps determine an engine's characteristics and performance potential.
The calculator uses the simple BSR formula:
Where:
Explanation: The ratio provides insight into whether an engine is oversquare (BSR > 1), square (BSR = 1), or undersquare (BSR < 1), each with different performance characteristics.
Details: BSR affects engine characteristics including power band, torque delivery, RPM capability, and engine size. Oversquare engines typically favor higher RPM operation, while undersquare designs favor low-end torque.
Tips: Enter bore and stroke measurements in millimeters. Both values must be positive numbers greater than zero for accurate calculation.
Q1: What is considered a good bore to stroke ratio?
A: There's no single "good" ratio - it depends on application. High-performance engines often have ratios around 1.1-1.3, while economy engines may have ratios around 0.8-1.0.
Q2: How does BSR affect engine performance?
A: Higher ratios (oversquare) typically allow higher RPM operation and horsepower, while lower ratios (undersquare) favor torque production at lower RPMs.
Q3: Can BSR be used to determine engine displacement?
A: No, BSR alone doesn't determine displacement. Displacement is calculated using both bore and stroke measurements along with the number of cylinders.
Q4: Are there limitations to the BSR concept?
A: While useful, BSR is just one design parameter. Other factors like valve timing, combustion chamber design, and forced induction significantly impact actual engine performance.
Q5: What's the typical BSR range for production engines?
A: Most production engines have BSR values between 0.8 and 1.2, with modern engines trending toward higher (oversquare) ratios for efficiency.