Fuel Temp/ Rack Relationship

This is the relationship between the Fuel temperature and Fuel Position take from a C16 7CZ ECM.
This is @ Full rack position and shows how the Fuel Temperature affects the Fuel position.
Key points are 89C (192f) is the max temp you can use before defaulting back.
70c (158f( is the Min temp for max gain.
Maximum Fuel position gain in best case would be @ 0.37 Fuel position. To work out what gain you might see in your own truck check the running temperature of your fuel whilst at operating temperature and under load and plot that.. For example if I was to see an average Fuel temp of 60c ( 140f) then I would have a gain in fuel position from 9.60 to 9.69 (0.06) Hardly worth the effort really. If your fuel temp was @ 89C (192f) then there would be Zero Gain. In colder climates with very low ambient you may well see a noticeable gain.

 

Interestingly with 250KPA of boost we see a larger possible gain of a magnitude of some 0.55 Fuel Position.
Total Fuel position is directly proportional to Boost/RPM . Testing the ECM whilst simulating full Load and Max boost gives us an interesting result.
This still needs to be compared to operating Fuel temps in a working environment to ascertain fuel position gain if any. The Fuelmap scaling applies so we see the same logic. here we see a Fuel position of 11.82 @ 89c.

 

Or Fuel position in some. commonly known/referred to as rack.