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.
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:
Variable |
Description |
IRL |
Intake Runner Length (cm) |
PT |
Peak Torque RPM |
Calculation Example
Step |
Calculation |
Peak Torque RPM (PT) |
4000 RPM |
Intermediate Value |
|
Multiply by 4.3 |
|
Add to 17.8 |
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 |