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#1 |
![]() Join Date: Aug 2006
Location: McLean, VA
Posts: 3,712
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Out of curiosity, anyone know how our ECM or BCM calculates these figures? Is this based on injector pulse count? Does fuel level contribute to these calculation?
I deleted secondaries and, as a result, both injectors fire pretty much all the time. And yet, average MPG reads reasonable although I haven't back checked mathematically with mileage vs. amount of fuel to fill up. I was just curious if anyone knew how displayed average MPG is calculated by ECM. |
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#2 |
![]() Join Date: Nov 2011
Location: Dunbarton NH
Posts: 7,378
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Good question, I'd like to add to it. How does the car know how much gas is in the tank? For mileage calculations, that needs to be a very accurate number. I suspect more accurate than the fuel gauge can read.
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#3 |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,697
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Doesn't matter whether you have 2 or 1 injector firing, the total PW will be the same. Motor does not use more fuel just because 2 injectors are on. The ECM splits the PW between the 2 injectors. VE is VE. The MPG calc GM uses is a combo of the Inj. PW and pulse counts from the VSS. Don't know about the range calc and the fuel gauge. Looks like a bit of a SWAG for me.
__________________
[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
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#4 | |
![]() Join Date: Aug 2006
Location: McLean, VA
Posts: 3,712
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I think I will start logging miles driven and gallons used and do some calculation to see how accurate MPG calls/display is. |
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#5 |
![]() Join Date: Jan 2010
Location: Mystic CT
Posts: 2,623
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FWIW:
On my car, the gas mileage shown on the dashboard is always about 10% low compared to measuring the old fashioned way |
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#6 |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,697
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Don't forget the error from tire and wheel size.
__________________
[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
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