1. What Is Compression Ratio Of Petrol Engine?

The compression ratio of a petrol engine is the ratio of the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke to the volume when the piston is at the top of its stroke. It represents how much the air-fuel mixture is compressed before ignition.

2. How Does The Calculator Work?

The calculator uses the compression ratio formula:

Where:

• \( \text{Swept Volume} \) — Volume displaced by the piston moving from bottom to top dead center (cm³)
• \( \text{Clearance Volume} \) — Volume remaining in the cylinder when the piston is at top dead center (cm³)

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

3. Importance Of Compression Ratio Calculation

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

4. Using The Calculator

Tips: Enter both swept volume and clearance volume in cubic centimeters (cm³). 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 petrol engines?
A: Most modern petrol 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 generally improve thermal efficiency and power output, but may increase the risk of engine knocking and require higher octane fuel.

Q3: What's the difference between static and dynamic compression ratio?
A: Static compression ratio (calculated here) is based on geometric volumes, while dynamic compression ratio accounts for valve timing and airflow characteristics during actual engine operation.

Q4: Can I increase my engine's compression ratio?
A: Yes, through methods like milling the cylinder head, using higher-dome pistons, or reducing combustion chamber volume, but this may require engine modifications and higher-octane fuel.

Q5: What happens if compression ratio is too high?
A: Excessively high compression ratios can cause pre-ignition or knocking, potentially leading to engine damage, and may require special fuels or engine management systems.