1. What is Intake Runner Length?

The intake runner length is a critical dimension in engine design that affects the engine's torque curve and powerband. It's calculated based on the pressure wave dynamics in the intake system at specific engine speeds.

2. How Does the Calculator Work?

The calculator uses the intake runner length formula:

Where:

• \( Length \) — Intake runner length (inches)
• \( duration \) — Camshaft duration (degrees)
• \( V \) — Pressure wave speed (ft/s, typically 1100-1300 ft/s)
• \( RPM \) — Engine speed where you want peak torque (rpm)

Explanation: The formula calculates the optimal intake runner length to time the return of the intake pressure wave for maximum cylinder filling at your target RPM.

3. Importance of Intake Runner Length

Details: Proper intake runner length tuning can significantly improve engine performance by enhancing volumetric efficiency at specific RPM ranges. Shorter runners favor high-RPM power, while longer runners boost low-end torque.

4. Using the Calculator

Tips: Enter camshaft duration in degrees (typically 260-300° for street engines), wave speed (use 1100 ft/s as default), and target RPM for peak torque. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical wave speed value?
A: For most applications, 1100 ft/s is a good starting point. This can vary from 1000-1300 ft/s depending on intake air temperature and runner design.

Q2: How does cam duration affect runner length?
A: Longer cam durations generally require shorter intake runners to maintain proper wave timing at higher RPMs.

Q3: Can I use this for exhaust primary length?
A: No, exhaust tuning uses different formulas accounting for exhaust gas temperature and different wave behavior.

Q4: What if my calculated length is impractical?
A: Many engines use tuned intake manifolds with runners that are compromises between ideal length and packaging constraints.

Q5: Does runner diameter matter?
A: Yes, diameter affects flow velocity and wave dynamics but isn't accounted for in this simple formula. Smaller diameters increase velocity but may restrict flow.