Question:
A petrol engine has compression ratio from:
A petrol engine has compression ratio from:
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Petrol engine → low compression ratio; Diesel engine → high compression ratio.
Updated On: May 22, 2026
- 6 to 10
- 10 to 15
- 15 to 25
- 25 to 40
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The Correct Option is A
Solution and Explanation
Concept:
Compression ratio is defined as:
\[
r = \frac{V_{max}}{V_{min}}
\]
where:
• \(V_{max}\) = volume before compression (BDC)
• \(V_{min}\) = volume after compression (TDC)
Step 1: Understand petrol vs diesel engines.
Petrol engines use spark ignition, while diesel engines use compression ignition.
Step 2: Reason for lower compression ratio in petrol engines.
Petrol engines are prone to knocking if compression ratio is too high. Therefore, compression ratio must be kept lower.
Step 3: Standard range.
Typical petrol engine compression ratio: \[ 6 \text{ to } 10 \] Diesel engines have much higher compression ratios (around 15–25). Final Answer: \[ \boxed{6 \text{ to } 10} \]
• \(V_{max}\) = volume before compression (BDC)
• \(V_{min}\) = volume after compression (TDC)
Step 1: Understand petrol vs diesel engines.
Petrol engines use spark ignition, while diesel engines use compression ignition.
Step 2: Reason for lower compression ratio in petrol engines.
Petrol engines are prone to knocking if compression ratio is too high. Therefore, compression ratio must be kept lower.
Step 3: Standard range.
Typical petrol engine compression ratio: \[ 6 \text{ to } 10 \] Diesel engines have much higher compression ratios (around 15–25). Final Answer: \[ \boxed{6 \text{ to } 10} \]
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