Thread: Stage 2 MPG
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Old 11-24-2012, 05:46 PM   #22
the suicidal eggroll
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Member#: 51961
Join Date: Jan 2004
Chapter/Region: RMIC
Location: Broomfield, CO
2005 STi
2012 WRX


Originally Posted by Elky View Post
Wouldn't some of the difference between the ecu vs pump mileage calculations have to do with the fact that the ecu does its math based off of injector duty cycle? Correct me if I'm wrong but wouldn't that be a more accurate metric than the pump which measures to 1/1000 of a gallon (which is 0.128 oz.)? Also I seem to recall a study saying that pumps are often off by up to 1/8 of a gallon per fill up.
Even with a 1/8 gallon error at the pump its FAR more accurate than the dash display. The dash display has been proven to be incredibly inaccurate by many people over the course of many years. Just a couple of months ago I filled up my bone stock '12 and hopped on the freeway. By the time I exited 15-20 miles later my mileage according to the dash display was over 34...and I was going uphill. My real mileage was closer to 27. A 1/8 gallon error out of 13 gallons is less than 1%, so if the calculation tells you it's 23, you might actually be at 23.2...I'll take that over the 20+% error on the dash display any day of the week.
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