Fuel Temperature Calculation

[thedbaz]

Hello,

in my 350z it has a stock fuel temperature sensor in the gas tank.

i have setup on an temp 3 as shown in the manual for fuel temperature. 

i have setup DI8 for the ethanol content sensor, which does fuel/ethanol temperature as well.

my question is on the how is the fuel density temperature calculated?

does it average these two temps together to get the temperature of the fuel and then apply the coefficient?

or does it use one or the other?

and if its just one, which one is it?

 

my ethanol content sensor is on the fuel return line right at the tank, so it is seeing the temperature of the fuel right before it enters the tank.

i would imagine that the gap between these two temperature will become less as the tank heats up and the longer the car runs.

 

[Adamw]

An analog fuel temp sensor takes preference over the flex sensor if both are enabled.  The reason for this is because the more common scenario is the flex sensor is at the back of the car (therefore less indicative of fuel temp in the rail) Vs an analog sensor is normally fitted in the rail.  In your case since the analog sensor is in the gas tank that would probably be less indicative of rail temp so I would suggest you turn that input off and it will use the flex sensor instead.

[thedbaz]

Hi Adam, thanks!!

ok so what you are really after is the fuel temp at the rails.

so with the the flex sensor reading the temp of the fuel coming back from the rails, that is more accurate.

ideally, it would be more beneficial if i moved the flex sensor to the regulator output. as it would be closer to the rails but not on the rails.

for the best accuracy, would you want to read the temp as the fuel enters the rail or as it leaves the rail?

[Adamw]

We are trying to calculate the density of the fuel entering the injector so this is ideally where we would measure temp.  Generally somewhere close to the rail - before or after will give similar results.