I think I see specifically what the discrepancy between instant and trip MPG is... Here is the log from a short signal gen run (Gallons and MPG are in thousandths)
Code:
,HI,uS, iC,VC,Mi,G, MPG, ,HI, uS, iC, vC, Mi,G, MPG
instant, 0,133228,54,83,10,0,48543, current, 0,133228, 54, 83, 10,0,48543
instant, 0,44084, 18,27,3, 0,44117, current, 0,177312, 72,110, 13,0,47445
instant, 0,44092, 18,28,3, 0,44117, current, 0,221404, 90,138, 16,0,46647
instant, 0,44056, 18,27,3, 0,44117, current, 0,265460,108,165, 20,0,48661
instant, 0,44092, 18,28,3, 0,44117, current, 0,309552,126,193, 23,0,48016
instant, 0,44064, 18,27,3, 0,44117, current, 0,353616,144,220, 26,0,47445
instant, 0,44064, 18,28,3, 0,44117, current, 0,397680,162,248, 30,0,48701
instant, 0,44080, 18,27,3, 0,44117, current, 0,441760,180,275, 33,0,48245
instant, 0,43032, 18,28,3, 0,45454, current, 0,484792,198,303, 36,0,47936
instant, 0,44044, 18,27,3, 0,44117, current, 0,528836,216,330, 40,0,48840
instant, 0,44068, 18,28,3, 0,44117, current, 0,572904,234,358, 43,0,48423
instant, 0,44060, 18,27,3, 0,44117, current, 0,616964,252,385, 46,0,48117
instant, 0,44044, 18,28,3, 0,44117, current, 0,661008,270,413, 50,1,48828
instant, 0,43072, 18,27,3, 0,45454, current, 0,704080,288,440, 53,1,48579
instant, 0,44064, 18,28,3, 0,44117, current, 0,748144,306,468, 57,1,49180
instant, 0,44068, 18,27,3, 0,44117, current, 0,792212,324,495, 60,1,48859
instant, 0,44072, 18,28,3, 0,44117, current, 0,836284,342,523, 63,1,48611
instant, 0,44060, 18,27,3, 0,44117, current, 0,880344,360,550, 67,1,49120
instant, 0,45092, 18,28,3, 0,43478, current, 0,925436,378,578, 70,1,48814
instant, 0,44072, 18,27,3, 0,44117, current, 0,969508,396,605, 73,1,48569
instant, 0,44056, 18,28,3, 0,44117, current, 1, 13564,414,633, 77,1,49013
instant, 0,45080, 18,27,3, 0,43478, current, 1, 58644,432,660, 80,1,48750
instant, 0,44080, 18,28,3, 0,44117, current, 1,102724,450,688, 83,1,48566
instant, 0,44072, 18,27,3, 0,44117, current, 1,146796,468,715, 87,1,48931
instant, 0,44068, 18,28,3, 0,44117, current, 1,190864,486,743, 90,1,48754
instant, 0,44044, 18,27,3, 0,44117, current, 1,234908,504,770, 93,1,48589
instant, 0,44064, 18,28,3, 0,44117, current, 1,278972,522,798, 97,1,48915
instant, 0,44088, 18,27,3, 0,44117, current, 1,323060,540,825, 100,2,48756
instant, 0,44064, 18,28,3, 0,44117, current, 1,367124,558,853, 103,2,48607
instant, 0,44080, 18,27,3, 0,44117, current, 1,411204,576,880, 107,2,48903
instant, 0,44072, 18,28,3, 0,44117, current, 1,455276,594,908, 110,2,48758
instant, 0,43040, 18,27,3, 0,45454, current, 1,498316,612,935, 113,2,48643
instant, 0,44072, 18,28,3, 0,44117, current, 1,542388,630,963, 117,2,48933
instant, 0,44060, 18,27,3, 0,44117, current, 1,586448,648,990, 120,2,48800
instant, 0,43044, 18,28,3, 0,45454, current, 1,629492,666,1018,124,2,49089
1629492,666,1018
The sums for the instant columns data model exactly match the trip columns, so that isn't the problem (and is good to know). But the instant mpg is only working with .003 miles, which introduces a wide margin of error. I think in the case of instant we need to work directly with vss tics(27/28) for now, eventually we should measure the microseconds between pulses for an indication of instant distance/fuel.