1. What is a Compression Ratio Calculator?

Definition: This calculator determines the compression ratio of an engine based on swept volume and clearance volume.

Purpose: It helps engine builders and performance enthusiasts calculate the compression ratio which affects engine efficiency and power output.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( CR \) — Compression Ratio (unitless)
• \( swept \) — Swept volume (cc)
• \( clearance \) — Clearance volume (cc)

Explanation: The total cylinder volume at bottom dead center (swept + clearance) is divided by the volume at top dead center (clearance).

3. Importance of Compression Ratio

Details: Compression ratio affects engine efficiency, power output, fuel requirements, and thermal efficiency. Higher ratios typically mean more power but may require higher octane fuel.

4. Using the Calculator

Tips: Enter the swept volume (displacement per cylinder) and clearance volume (combustion chamber volume) in cubic centimeters (cc). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical compression ratio?
A: Street engines: 8:1 to 10:1, Performance engines: 10:1 to 13:1, Race engines: 13:1 and higher.

Q2: How do I measure clearance volume?
A: Use a burette to measure liquid volume in the combustion chamber at TDC with piston and head gasket installed.

Q3: Does this account for head gasket volume?
A: Head gasket volume should be included in your clearance volume measurement.

Q4: What's the relationship between CR and octane?
A: Higher compression ratios typically require higher octane fuel to prevent detonation.

Q5: How does CR affect power and efficiency?
A: Higher CR generally increases both power output and thermal efficiency, up to the point where detonation occurs.