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Old 04-07-2008, 01:46 AM   #14 (permalink)
cfg83
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1999 Saturn SW2 - '99 Saturn SW2 Wagon
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Chris -

Quote:
Originally Posted by Chris D. View Post
how does a scanguage give you accurate fuel used data? does it know the size of your fuel tank, your injector pulse rates, voltage to the pump, regulator settings?

I dont see how it could be any more accurate than anything else..
I agree, so I don't use the SG for reporting my MPG. I use the GPS adjusted odometer and multiple tank fill-ups for my fuel log. The SG has a "cheat bias" that you use to calibrate fill-ups. If you change the way you drive between fill-ups, or you're driving context changes, there is the possibility that the cheat bias would lose validity between fill-ups.

The SG requires that you input the size of the engine in liters, a speed adjustment based on non-OEM tire size changes, and the tank size.

From what I can tell, the SG does not know about injector pulses, 02 sensors, or fuel trim. If it did, I would expect it to report that data in the instant gauges, but it doesn't.

I only trust long term MPG, so I look at my MPG over 90 day fill-ups. The problem with my methodology is that is is harder for me to claim improvement of mods that have small effects on MPG.

I think the SG is a fantastic *relative* MPG barometer. With all else being equal, it can tell you that you are increasing or decreasing MPG consumption.

CarloSW2
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