The formula to calculate the Effective Compression Ratio (ECR) is:
\[ ECR = CR \times \left(1 + \frac{B}{14.7}\right) \]
Where:
Let's say the compression ratio (CR) is 10 and the boost (B) is 7 psi. Using the formula:
\[ ECR = 10 \times \left(1 + \frac{7}{14.7}\right) \approx 14.76 \]
So, the Effective Compression Ratio (ECR) is approximately 14.76.
Definition: The compression ratio 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.
Formula: \( \text{Compression Ratio} = \frac{\text{Swept Volume} + \text{Clearance Volume}}{\text{Clearance Volume}} \)
Example: \( \text{Compression Ratio} = \frac{600 + 50}{50} \)
Definition: The effective compression ratio takes into account the boost pressure from forced induction.
Formula: \( \text{Effective Compression Ratio} = \left( \frac{\text{Boost Pressure}}{14.7} + 1 \right) \times \text{Static Compression Ratio} \)
Example: \( \text{Effective Compression Ratio} = \left( \frac{10}{14.7} + 1 \right) \times 9 \)
Definition: Increasing the compression ratio can improve engine performance and efficiency.
Methods:
Example: If the current compression ratio is 8:1, using a thinner head gasket can increase it to 8.5:1.
Definition: The optimal compression ratio for boosted engines balances power and detonation resistance.
Guideline: For most street engines, an effective compression ratio of around 12:1 is recommended.
Example: A static compression ratio of 8:1 with 10 psi of boost results in an effective compression ratio of approximately 12:1.
