By Brad Adair
Need some tips and tricks to help you determine your fuel line diameter?
Fuel line diameter matters A LOT!
A larger diameter is generally better, but the correct diameter is the best choice.
If the diameter is too small: you won’t be able to support your horsepower goal.
If the diameter is too big: the lines will take longer to pressurize.
If your pump can't maintain the pressure, it can drop during times of high demand, leading to engine damage.
It is an unnecessary expense, bigger is more expensive.
General Principles
Many in-line fuel pump manufacturers recommend a fuel line diameter that works best with their pumps. This prevents starving the pump and is not the necessarily the size of the outlet line.
Ethanol will require about 30% more fuel than gasoline to generate the same HP. Methanol will require double the amount of fuel than gasoline. When designing a fuel line system for these fuels, go one and two sizes larger than the gasoline requirement. The return lines, which are the fuel lines after the regulator, can generally be one size smaller than the feed line.
Return lines (the fuel line after the regulator) can generally be one size smaller than the feed line.
Here is a chart we've created to give you a general idea and possibly make the decision for you, when choosing a fuel line diameter.
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