1. What is Dynamic Compression Ratio?

The Dynamic Compression Ratio (DCR) is a more accurate measure of an engine's compression than static compression ratio because it accounts for when the intake valve closes during the compression stroke. This makes it particularly useful for performance engine building and tuning.

2. How Does the Calculator Work?

The calculator uses the Wallace Racing formula:

Where:

• \( Displacement \) — Total engine displacement in cubic centimeters (cc)
• \( IVC \) — Intake valve closing angle in degrees after bottom dead center
• \( Clearance\ Volume \) — Combustion chamber volume in cc

Explanation: The formula calculates the actual compression ratio based on when the intake valve closes, which affects how much air/fuel mixture gets compressed.

3. Importance of DCR Calculation

Details: DCR is critical for determining optimal camshaft selection, preventing detonation, and maximizing engine performance while maintaining reliability with available fuel octane.

4. Using the Calculator

Tips: Enter displacement in cc, IVC in degrees (after BDC), and clearance volume in cc. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why use DCR instead of static compression ratio?
A: DCR accounts for camshaft timing and gives a more accurate picture of the actual compression the engine experiences.

Q2: What's a good DCR for pump gas engines?
A: Typically 8.0:1 or lower for 87 octane, up to about 8.5:1 for premium 93 octane, depending on other factors.

Q3: How do I find my IVC angle?
A: IVC is specified in camshaft specifications or can be calculated from cam timing numbers.

Q4: Does DCR affect engine power?
A: Yes, higher DCR generally means more power, but must be balanced against fuel octane limitations.

Q5: What clearance volume should I use?
A: This is the combustion chamber volume including head gasket thickness and piston dish/dome volume.