Gelf VXR
December 3rd, 2015, 05:05 PM
You don't find many forum posts regarding fuel temperature density correction.
Fuel density changes ~5.5% over a range of 50°C (, -10,1.0277, 0,1.01662, 10,1.00554, 20,0.99446, 30,0.98338, 40,0.9723)
I guess the trims cope adjusting fueling to account this difference, from season to season it would explain if trims are going positive in hot weather, negative in cold weather.
The injector flow modifier for IAT seems to be the candidate for making corrections for fuel temp, its generally set at 1 for all temps, but Ive seen the LS7 or LS9 with different values at high IAT, factor <1, it looks as thou reducing flow to compensate for less dense air, I thought MAF or GMVE would calibrate for this? So i think it must be to compensate for less dense fuel.
The IAT modifier is linear with change in fuel density as below, graph attached
T*___LS9_______Change in Fuel Density
40___0.986024__0.9723
50___0.971986__0.96122
60___0.961976__0.95014
70___0.95398___0.93906
80___0.947999__0.92798
Normally minimum IAT would be equal to ambient, or higher, so using the below values would compensate for change in fuel density <1 as fuel temps increase, density decreases, >1 as temps decrease, density increases. Fuel density is normally shown at 15°C which would be factor 1.
(, -40,1.06094, -30,1.04986, -20,1.03878, -10,1.0277, 0,1.01662, 10,1.00554, 20,0.99446, 30,0.98338, 40,0.9723, 50,0.96122, 60,0.95014, 70,0.93906, 80,0.92798, 90,0.9169, 100,0.90582, 110,0.89474, 120,0.88366)
Any thoughts, being done already?
Fuel density changes ~5.5% over a range of 50°C (, -10,1.0277, 0,1.01662, 10,1.00554, 20,0.99446, 30,0.98338, 40,0.9723)
I guess the trims cope adjusting fueling to account this difference, from season to season it would explain if trims are going positive in hot weather, negative in cold weather.
The injector flow modifier for IAT seems to be the candidate for making corrections for fuel temp, its generally set at 1 for all temps, but Ive seen the LS7 or LS9 with different values at high IAT, factor <1, it looks as thou reducing flow to compensate for less dense air, I thought MAF or GMVE would calibrate for this? So i think it must be to compensate for less dense fuel.
The IAT modifier is linear with change in fuel density as below, graph attached
T*___LS9_______Change in Fuel Density
40___0.986024__0.9723
50___0.971986__0.96122
60___0.961976__0.95014
70___0.95398___0.93906
80___0.947999__0.92798
Normally minimum IAT would be equal to ambient, or higher, so using the below values would compensate for change in fuel density <1 as fuel temps increase, density decreases, >1 as temps decrease, density increases. Fuel density is normally shown at 15°C which would be factor 1.
(, -40,1.06094, -30,1.04986, -20,1.03878, -10,1.0277, 0,1.01662, 10,1.00554, 20,0.99446, 30,0.98338, 40,0.9723, 50,0.96122, 60,0.95014, 70,0.93906, 80,0.92798, 90,0.9169, 100,0.90582, 110,0.89474, 120,0.88366)
Any thoughts, being done already?