Fuel injector flow; if you swapped injectors, especially to a type rated at a psi different than 43.5. In that case, divide 43.5 by the other injector's test psi (39 for Ford/Bosch). Take the square root of the number (to remove the square from "pounds per square inch [psi]), and then multiply that by the new injector's rated flow. For example, if you're using the Ford SVO/Bosch style, you'll want to multiply their rating by 1.056 (24#=25.34, 30#=31.68, 36#=38.02, 42#=44.35, etc.).

12-17-2006, 12:04 PM
injuneer, what do you mean by set the injectors rated flow to your fuel system pressure. are you talking about using an adjustable fuel pressure regulator? Like 43.5 psi?

You have to tell the PCM the injector's "flow constant". And that number has to be adjusted to reflect the actual fuel system operating pressure, if the fuel system pressure is not the same pressure the injector was flow rated at.

A 24#/HR SVO injector is flow rated at 2.7bar (39.15psi). If you put that injector in an LT1 with a STOCK fuel system pressure of 3.0bar (43.5psi), the injector will flow about 5% higher than it is rated.

(43.5 / 39.15) ^0.5 = (1.111) ^0.5 = 1.0541

The 24# SVO needs an injector constant of 24 X 1.0541 = 25.298#/HR

Or, if you are using LS1 injectors (flow rated at 4bar = 58.0psi) in an LT1, you will find that a 28# LS1 injector is actually about the same flow rating.....

(43.5 / 58.0) ^0.50 = (0.75) ^0.50 = 0.866

The 28# LS1 flow constant needs to be set at 28 x 0.866 = 24.289#/HR