1. What is Compression Ratio?

The Compression Ratio (CR) is a fundamental specification in internal combustion engines that compares the volume of the cylinder when the piston is at the bottom of its stroke to the volume when the piston is at the top of its stroke.

2. How Does the Calculator Work?

The calculator uses the Compression Ratio formula:

Where:

• \( swept\ volume \) — Volume displaced by the piston (cubic units)
• \( clearance\ volume \) — Volume remaining when piston is at top dead center (cubic units)

Explanation: The ratio shows how much the air-fuel mixture is compressed before ignition, which affects engine efficiency and power.

3. Importance of Compression Ratio

Details: Higher compression ratios generally lead to greater thermal efficiency and power output, but may require higher octane fuels to prevent knocking. Typical values range from 8:1 to 12:1 in gasoline engines.

4. Using the Calculator

Tips: Enter both swept volume and clearance volume in the same cubic units (cc, liters, etc.). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical compression ratio for gasoline engines?
A: Most modern gasoline engines have compression ratios between 9:1 and 12:1. High-performance engines may go higher.

Q2: How does compression ratio affect fuel requirements?
A: Higher compression ratios typically require higher octane fuels to prevent premature combustion (knocking).

Q3: What's the difference between static and dynamic compression ratio?
A: Static CR is what this calculator measures. Dynamic CR accounts for valve timing and is typically lower.

Q4: Why do diesel engines have higher compression ratios?
A: Diesel engines rely on compression ignition, typically needing ratios of 14:1 to 22:1.

Q5: Can I increase my engine's compression ratio?
A: Yes, through modifications like milling the head or using different pistons, but this requires careful planning and fuel considerations.