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Intake Runner Length Calculator

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You can determine the optimal length for your engine’s intake runner with the Intake Runner Length Calculator. Enter the peak torque RPM and it finds the ideal length. This ensures best engine performance.

Intake runner length measures the distance air passes from intake manifold to combustion chamber. Variations change engine dynamics, especially power and efficiency.

Intake Runner Length Calculator

Enter any one value to calculate the missing variable.







Tool User Guide

Input Action
Peak Torque RPM (PT) Enter the engine RPM at peak torque (e.g., 4000 RPM).
Intake Runner Length (IRL) Input known runner length to find peak torque RPM.

Input Examples

Peak Torque RPM Intake Runner Length (cm)
3000 48.7
5000 39.3
6000 35.0

Formula for Intake Runner Length

Calculate the intake runner length with:

IRL=17.8+(10PT10001)×4.3
 
Variable Description
IRL Intake Runner Length (cm)
PT Peak Torque RPM

Calculation Example

Step Calculation
Peak Torque RPM (PT) 4000 RPM
Intermediate Value 1040001000=610 – \frac{4000}{1000} = 6
Multiply by 4.3 6×4.3=25.86 \times 4.3 = 25.
Add to 17.8 17.8+25.8=43.617.8 + 25.8 = 43. cm

Answer: The intake runner length is 43.6 cm

Intake Runner Length Chart

Engine RPM Range Desired Torque Peak RPM Runner Length (inches) Runner Length (cm)
2000-4000 RPM 3000 RPM 16-18 inches 40.6-45.7 cm
4000-6000 RPM 5000 RPM 12-14 inches 30.5-35.6 cm
6000-8000 RPM 7000 RPM 8-10 inches 20.3-25.4 cm
8000-10000 RPM 9000 RPM 6-8 inches 15.2-20.3 cm
10000+ RPM 11000+ RPM 4-6 inches 10.2-15.2 cm
 

 

 

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