1. What is Compression Ratio?

Compression Ratio (CR) is a fundamental parameter in engine design that represents the ratio of the maximum to minimum volume in the cylinder of an internal combustion engine. It indicates how much the air-fuel mixture is compressed before ignition.

2. How Does the Calculator Work?

The calculator uses the compression ratio formula:

Where:

• \( Swept\ Volume \) — Volume displaced by the piston (L)
• \( Clearance\ Volume \) — Volume remaining when piston is at top dead center (L)

Explanation: The formula calculates how much the air-fuel mixture is compressed by comparing the total cylinder volume to the minimum volume at compression.

3. Importance of Compression Ratio

Details: Compression ratio directly affects engine efficiency, power output, fuel economy, and emissions. Higher compression ratios generally lead to better thermal efficiency but may require higher octane fuels to prevent knocking.

4. Using the Calculator

Tips: Enter swept volume and clearance volume in liters. Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical compression ratio for gasoline engines?
A: Most modern gasoline engines have compression ratios between 8:1 and 12:1, with some high-performance engines reaching up to 14:1.

Q2: How does compression ratio affect engine performance?
A: Higher compression ratios increase thermal efficiency and power output but may cause knocking if fuel octane rating is insufficient.

Q3: What's the difference between static and dynamic compression ratio?
A: Static compression ratio is calculated from geometric measurements, while dynamic compression ratio accounts for valve timing and actual cylinder filling.

Q4: Why do diesel engines have higher compression ratios?
A: Diesel engines typically have compression ratios of 14:1 to 25:1 because they rely on compression ignition rather than spark ignition.

Q5: Can compression ratio be changed in an existing engine?
A: Yes, through modifications like changing piston design, cylinder head milling, or using different thickness head gaskets, though these changes require careful engineering consideration.