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Thread: MPG Gauge

  1. #1
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    MPG Gauge

    It would be nice to have an instant and average MPG gauge for the Ecotuners.

  2. #2
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    you can create your own MPG in Hpt. There is a tool that allows you to create gauges based on sensor inputs. There are also some function tools so you can take the fuel consumed by the injectors and the distance traveled.

  3. #3
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    That would be interesting, is there a write up on how to do this?

  4. #4
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    In for answers
    15 C7Z M7

  5. #5
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    After some googling I came across this formula

    i noticed, and i'm going through my notes to come up with it now.

    A*(1/3600000)*(16.7)*(3)*E*(60)*(2)

    creates fuel flow in lb/hr

    A is BPW and E is RPM

    the 1/3600000 is for creating the "hr" portion, since there are 3.6 million mSec in one hour.

    the 16.7 is injector flowrate

    the 3 is half of the number of cylinders

    the 60.... i'm not sure off-hand why it was needed, but it's there for a reason.

    and finally, the 2 is how many pulses of the injectors there are in 1 4-stroke cycle.(2 in the case of double-fire MPFI)



    now i create fuel flow in gallons/hr

    A/6.073

    6.073 being how much a single gallon of fuel weighs. it can and will change a lot based on fuel composition, but that's a reference number.



    now i create MPG thus:

    A/B

    A being MPH, B being fuel flow in gallons/hr

    so miles per hour / gallons per hour = miles / gallon.



    make sense?
    15 C7Z M7

  6. #6
    Tuner in Training Solace's Avatar
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    anyone have a step by step for creating this function to suit a neanderthal?
    Bertram 23 Flybridge
    Chev 5.3LS swapped and going well

  7. #7
    Here you go.

    Go into VCM Scanner... Tools menu... Math Parameters... then go into the user defined section.

    In the first unused entry:
    Name: MPG.

    Abreviation
    : MPG.

    Notes
    : Instantaneous MPG

    Expression: (200-6*[82.155])*[50020.114]/[6210.72]/[50151.248.avg(700)]/[50070.56]
    You can paste it.

    Unit: One

    Decimals: 0

    In case anything isn't detected:

    200 is the constant used to convert units. Change to 400 for V8 and 300 for V6. You can also adjust this value up or down to calibrate the gauge.

    [82] = Ethanol Fuel % (SAE)
    [50020] = Vehicle Speed [Sensor] (mph)
    [6210] = Injector Flow Rate (lb/h)
    [50151] = Injector Pulse Width - Bank 1[Sensor] (s)
    [50070] = Engine Speed (rpm)

    If you don't have an ethanol sensor (most of you won't), replace [82.155] with 10 for E10 or 85 for E85 or whatever you fuel with.

    Now you can plug MPG into a Gauge or Graph or Chart.

    MPG in a Ellipse Gauge to match your RPM and Speed is neat.
    MPG in a graph with RPM across the top and Vehicle Speed on the left (in 5 mph increments) is useful. You could also do Cylinder Airmass on the left to match your Timing graphs. I have both.
    MPG in a Chart also works.

    Enjoy!
    Last edited by TownDrunk; 04-07-2017 at 07:24 PM. Reason: added average to the injector pulse width

  8. #8
    Quote Originally Posted by fastrunner08 View Post
    There are also some function tools so you can take the fuel consumed by the injectors and the distance traveled.
    Mpg Average couldn't get any easier:

    Name: MPG Avg
    Abbreviation: MPGa
    Notes: Trip MPG
    Expression: [7255]
    Unit: One
    Decimals: 1

    7255 = MPG Fuel Economy This Trip.

    This is untested. I bricked my ECM and still waiting for Support to get me going.
    Last edited by TownDrunk; 03-27-2017 at 05:57 PM.

  9. #9
    Tuner in Training Solace's Avatar
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    wow! thanks guys- got these loaded and ready to go this coming weekend- be prettyinteresting as ill be doing 12-18hours running over two days weather permitting.
    Bertram 23 Flybridge
    Chev 5.3LS swapped and going well

  10. #10
    Please update this thread with any changes you need.

  11. #11
    Tuner in Training Solace's Avatar
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    Oh hey is this the corrrect way to make a guage read in Knots from Mph in the math expression box?

    [50020.114]*1.15077944802

    cheers again guys
    Bertram 23 Flybridge
    Chev 5.3LS swapped and going well

  12. #12
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    I'm afraid I am in neanderthal class for this one too: I see it's allowing for e.g. E85 fuel etc... but in <MY> country only good ol' 98 (ish) octane petrol is available.. sooo what numbers to plug in there THEN?? Presumably this whole part : (31.75*6.0-5*[82.155]) has to be replaced by some constant(?) Can't be 0, obviously...
    99 TA, Texas Speed LS376, PRC heads, 233/239 cam, Fast 92mm, 95mm TB, card style MAF, Tick TR6060, Strange 4.11 12 bolt axle & clutchpack diff, Strano springs/dampers, Vette 18" wheels, Vette disks, CTS-V calipers, 16lb flywheel, long tube headers, no cats.

  13. #13
    Quote Originally Posted by Solace View Post
    Oh hey is this the correct way to make a gauge read in Knots from Mph in the math expression box?

    [50020.114]*1.15077944802

    cheers again guys
    I think you need to multiply by 0.868976, not 1.1

    Quote Originally Posted by dermotw View Post
    I'm afraid I am in neanderthal class for this one too: I see it's allowing for e.g. E85 fuel etc... but in <MY> country only good ol' 98 (ish) octane petrol is available.. sooo what numbers to plug in there THEN?? Presumably this whole part : (31.75*6.0-5*[82.155]) has to be replaced by some constant(?) Can't be 0, obviously...
    We don't care about octane, only the ethanol part since it requires a higher injector rate. It should say on the pump if you have ethanol added, at least in the US they do. Nothing wrong with using zero, but just for the sensor: [82.155].

  14. #14
    Tuner in Training Solace's Avatar
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    Heh yeah you're right, should have stayed in school longer i guess!
    Bertram 23 Flybridge
    Chev 5.3LS swapped and going well

  15. #15
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    Smile

    Quote Originally Posted by TownDrunk View Post
    We don't care about octane, only the ethanol part since it requires a higher injector rate. It should say on the pump if you have ethanol added, at least in the US they do. Nothing wrong with using zero, but just for the sensor: [82.155].
    Ahh ok got you, thanks! -yes, hmm I will experiment with it a bit, see what it says...
    99 TA, Texas Speed LS376, PRC heads, 233/239 cam, Fast 92mm, 95mm TB, card style MAF, Tick TR6060, Strange 4.11 12 bolt axle & clutchpack diff, Strano springs/dampers, Vette 18" wheels, Vette disks, CTS-V calipers, 16lb flywheel, long tube headers, no cats.

  16. #16
    I updated the expression to make it less twitchy.

    The second to last field now has a 700ms averaging added to it so now the mpg should only vary 1, maybe 2 mpg at a time.

    [50151.248.avg(700)]

  17. #17
    S2H aka SoundEngineer aka Scott was the source for my MPG gauge: https://www.hptuners.com/forum/showt...eated-by-Users

    My gauge assumes a Chevy 4 cyl. If my version doesn't work, see that thread for ideas.

  18. #18
    Here's another MPG gauge: https://www.hptuners.com/forum/showt...l=1#post132529

    Sam Michael fixed the original formula and is the one I used above. I couldn't find the reference to adjusting the formula for E85 so that'll have to be a big unknown.

    I adjusted the formula a bit, changing -5*ethanol% to -6 for upper ethanol blends. This adjusts the gauge for about 15% loss using E85. If you have larger loss with E85, you could increase that to 6.5 or 7.

    I also simplified the left side of the formula (the constant) with directions on how to adjust for 6 cyl or 8 cyl.
    Last edited by TownDrunk; 04-07-2017 at 07:18 PM.

  19. #19
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    Quote Originally Posted by TownDrunk View Post
    Here you go.

    Go into VCM Scanner... Tools menu... Math Parameters... then go into the user defined section.

    In the first unused entry:
    Name: MPG.

    Abreviation
    : MPG.

    Notes
    : Instantaneous MPG

    Expression: (200-6*[82.155])*[50020.114]/[6210.72]/[50151.248.avg(700)]/[50070.56]
    You can paste it.

    Unit: One

    Decimals: 0

    In case anything isn't detected:

    200 is the constant used to convert units. Change to 400 for V8 and 300 for V6. You can also adjust this value up or down to calibrate the gauge.

    [82] = Ethanol Fuel % (SAE)
    [50020] = Vehicle Speed [Sensor] (mph)
    [6210] = Injector Flow Rate (lb/h)
    [50151] = Injector Pulse Width - Bank 1[Sensor] (s)
    [50070] = Engine Speed (rpm)

    If you don't have an ethanol sensor (most of you won't), replace [82.155] with 10 for E10 or 85 for E85 or whatever you fuel with.

    Now you can plug MPG into a Gauge or Graph or Chart.

    MPG in a Ellipse Gauge to match your RPM and Speed is neat.
    MPG in a graph with RPM across the top and Vehicle Speed on the left (in 5 mph increments) is useful. You could also do Cylinder Airmass on the left to match your Timing graphs. I have both.
    MPG in a Chart also works.

    Enjoy!
    I'm trying to get this to work on my 8.1L 2500, when I paste the formula as is, it doesn't function as I don't have a ethanol sensor, 3.jpg

    Changing it to 10, associates it with a fuel pressure sensor, I don't have. Changing it back to 85, it recognizes it as E85, but it's still red because I don't have a Flex sensor. Taking it out altogether results in numbers that go up and down, but seem wildly inaccurate. Without the [82.155], and with the 200 changed to 400 for V8, it shos like 40 mpg, which I definitely do not get. Putting the 400 back to 200 results in fairly reasonable numbers, but I still am seeing like 20+ at cruise, which is nearly double what I'm averaging.

    Any insights? I'm sure I've just gone wrong somewhere lol.

  20. #20
    Try: (400-6*10)*[50020.114]/[6210.72]/[50151.248.avg(700)]/[50070.56]

    You may have to tweak the 400 to make it more accurate.
    Last edited by TownDrunk; 01-04-2018 at 08:32 PM.