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# Fuel modifier for air temperature

### Tech Articles

Discussion and questions related to the course EFI Tuning Fundamentals

In the Tuning Fundamentals course it was mentioned that the fuel modifier for air temperature changes is not linear, but is actually an inverse sloping curve. It was also mentioned that we tend to approximate this curve with a straight line.

Can someone post a actual formula so that I can generate a curve given the 16 fixed temperature cells that I have for this modifier? I am using a Holley Dominator ECU.

Andrew

generally you would have something like this [img="blob:https://www.hpacademy.com/9683a880-1440-470e-9702-d10cec4c95aa" alt=""]

The link doesn't seem to be working...

Andrew

Anyone?

Andrew

If you want a formula, I think you are trying to calculate the mass of air so you can add the appropriate mass of fuel to achieve your target Air:Fuel Ratio.

Mass of air is determined by the ideal gas law.

PV = nRT (See https://en.wikipedia.org/wiki/Ideal_gas_law details)

so Mass (essentially the nR term) is PV/T. So the mass is inversely proportional to the absolute temperature. Seems like a linear relationship to me.