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Discussion Starter #1
Does anyone know how the calculated fuel rate works...as in how it is actually calculated? is it per injection or per period of time? and how can I use this to maximize my mileage? I ask this because at 65mph my CFR is lower in fifth gear than in sixth. Does this mean I am getting better mileage? The engine is reving a bit higher but I dunno. Would be curious to know.
 

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Discussion Starter #2
:help bump :help
 

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what are you asking?

how does the truck computer calculate mileage that shows up in the Drivers Information Center (DIC)?

you've worded your question confusedly, hence you're not getting much help.
 

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Discussion Starter #4
in my edge cts there is a guage that shows the Calculated fuel rate as a measure of mm3...What I'm wondering is what does that mm3 stand for...and if it is less in fifth gear than it is in sixth...am I using less fuel even though it is revving higher? hopefully that's easier to read. Thanks for the tip
 

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the DIC uses a table called main injection quantity, or something like that, to calculate the mileage.

I like to use the KISS method to get the best mileage...

Keep
It
Simple
Stupid

drive a tank in 5th and one in 6th on the same route, see which gets better hand calc'd mileage.
 

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in my edge cts there is a guage that shows the Calculated fuel rate as a measure of mm3...What I'm wondering is what does that mm3 stand for...and if it is less in fifth gear than it is in sixth...am I using less fuel even though it is revving higher? hopefully that's easier to read. Thanks for the tip
mm3/s should be millimeters cubed per second roughly the same as milliliters/second.
 

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...What I'm wondering is what does that mm3 stand for...and if it is less in fifth gear than it is in sixth...am I using less fuel even though it is revving higher?
It is a meaningless number, and is very misleading to those who subscribe to its volume implication, cubic millimeter. It has no relevance to actual fuel volume used. At best it is useful economy reference tool if gear and rpm stays constant.

It is a "per stroke" reference, not time dependent.
 

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Discussion Starter #8
could it be used to calculate gallons per hour or something like that?
 

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your not going to figure out mileage by mm3, it varies.

however you will get better mileage in 5th gear while towing. My truck runs with about a 10% less load in 5th than 6th at 75mph....try to keep your rpms around 2k and that should be your best bet for mileage.
 

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I contacted Edge and they told me it is mm3/minute as they just display the value that GM calculates in their module. I used it on my last trip out with the camper to determine if I needed to shift down. I found running the truck in 4th as to 5th (allison 6 sp with manual mode) dropped the value from 70 to 40 on hills of moderate grade and from 105 to 70 on the steep hills. Overall fuel economy went from 12.6 mpg to 13.6 mpg (18.6L/100Km to 17.3L/100Km). Also the egt dropped when shifting down, but engine and tanny temp rose.
 

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not to hijack but...

what sensors does the ecu use to caculate the fuel rate I am asking because my calculated fuel rate says no data as well as my baro. I have a new baro and all the wiring checks out I have used 2 diffrent ecu's and the same problem. I was wondering if the lack of data on the fuel rate is part of the reason I'm smoking a lot and also why the baro may read no data. also kinda wierd my boost pressure starts out at 12 psi I have been thru the entire boost sensor circut also good sensor and wiring ect. she is driving me batty any help?

Thanks,
Ken
 

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Discussion Starter #13
maybe your boost sensor is reading MAP or manifold absolute pressure...mine is usually thirteen where I live but if your up higher it could be twelve I think...as for the rest I don't know...sorry dude.... Bump anyway
 

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well I talked to a guy who is really good with em he said that the 12 psi at idle is normal he also said that my scan tool may not be able to read calc fuel rate or baro pressure I am using a auto enginuity does anyone know if they display that data or do I have another prob
 

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Why cant mm3 be used? If it is cubic millimeters fuel used per powerstroke, take and multiply RPM * 240 to get powerstrokes per hour then by your average or instant mm3 then divide by 3,785,411 to get gallons per hour. For instance, I turn 1800 RPM at 70MPH and average 27 Calc mm3 according to a recent efi live log.

1800 * 240 * 27 / 3,785,411 = 3.081 gal/hr

70 / 3.081 = 22.72 MPG

not too far off I think.. I'd like to create a custom PID in EFI Live scan to compute this on the fly.
 

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Has anyone confirmed this use of CFR to get fuel flow as "black6spdZ" mentions ? Other calcs or uses confirmed ?
 
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