How to calculate GPH on mefi4.adx

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pbusanga
Posts: 38
Joined: Sun Jun 03, 2012 2:06 pm

How to calculate GPH on mefi4.adx

Post by pbusanga »

is there anyway to calculate GPH (gallons per hour) in real time and calculate total gallons used as a cumulative figure, in total and per trip.

Would like to be able to use this software (i know is not intended for this) to calculate how many gallons i have used on my boat while underway.

bear in mind as this is a boat and not a car i do not have a speed sensor built into my defenition ADX file so cannot calculate MPG. i need to put a certain amount of gallons in boat and let the software monitor how many gallons i have used...am sure is possible someway ?

i would have to use the injector flow data in someway...
cbernhardt
Posts: 95
Joined: Fri Apr 18, 2008 5:19 am

Re: How to calculate GPH on mefi4.adx

Post by cbernhardt »

pbusanga wrote:is there anyway to calculate GPH (gallons per hour) in real time and calculate total gallons used as a cumulative figure, in total and per trip.

Would like to be able to use this software (i know is not intended for this) to calculate how many gallons i have used on my boat while underway.

bear in mind as this is a boat and not a car i do not have a speed sensor built into my defenition ADX file so cannot calculate MPG. i need to put a certain amount of gallons in boat and let the software monitor how many gallons i have used...am sure is possible someway ?

i would have to use the injector flow data in someway...
There is a native GPH item built into the MEFi4. What software are you using? If you are using the OBD Diagnostics software (aka MEFIBurn) there should be a GPH item already in your items list.

Since you do not have a speed sensor you cannot get an accurate MPG reading; however you could get something reasonable by using the RPM output. I did this with a car, but of course it was accurate only in high gear. In a boat this method would not be as accurate since there are many more variables other than RPM which affect the speed.

Charles
pbusanga
Posts: 38
Joined: Sun Jun 03, 2012 2:06 pm

Post by pbusanga »

oh ok i will look, i must have missed the GPH built in..too many late nights staring at screen :) )

yes am using the MEFI burn and tunerpro software.

could you explain to me the principle of linking to rpm..how would this work what is the relationship to GPH
cbernhardt
Posts: 95
Joined: Fri Apr 18, 2008 5:19 am

Post by cbernhardt »

You would have to know (or estimate) your boat's speed at a certain RPM. In the item list equation you would link both the RPM and the GPH. The RPM would have to have a factor that would convert it to the correct MPH. Then just divide the converted RPM (converted to MPH) by GPH.

In my case the equation was X /20/ Y, where X=RPM and Y=GPH. 20=factor to convert RPM to MPH. The factor for your boat will be much larger. Assume your boat is turning 2000 rpm at 10 mph, the factor would be 2000/10=200.

Charles
pbusanga
Posts: 38
Joined: Sun Jun 03, 2012 2:06 pm

Post by pbusanga »

Got it..thanks Charles.

the GPH item on mefi4 is an instantaneous gallon consumption figure. How would i convert that into actual gallons used from a given time.

ie when i start engine how could i accumulate gallons used ?
cbernhardt
Posts: 95
Joined: Fri Apr 18, 2008 5:19 am

Post by cbernhardt »

As far as I know there is no way to accumulate the total gallons used.

Charles
pbusanga
Posts: 38
Joined: Sun Jun 03, 2012 2:06 pm

Post by pbusanga »

ok thanks...hmm could be something to look into..considering we have fuel flow rates and engine hours and rpms all captured there should be some way to accumulate gallons used over time...

HI Mark maybe something that can be incorporated into your software ... :)

Could history tables be used in anyway for this ..
cbernhardt
Posts: 95
Joined: Fri Apr 18, 2008 5:19 am

Post by cbernhardt »

You can create a histogram showing the average GPH or MPG over the time that the engine parameters are being scanned, but not sure what use it would be.

Charles
robertisaar
Author of Defs
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Location: Camden, MI

Post by robertisaar »

one way to estimate fuel usage would be to take the GPH reading, average it(can be done with the histograms, then multiply it by the amount of time the engine has been running(done in hours to make the conversion easy).

avg 5 GPH over a 2 hour period = 10 gallons used

it's obviously not automatic, but it's fast to do.
pbusanga
Posts: 38
Joined: Sun Jun 03, 2012 2:06 pm

Post by pbusanga »

robertisaar wrote:one way to estimate fuel usage would be to take the GPH reading, average it(can be done with the histograms, then multiply it by the amount of time the engine has been running(done in hours to make the conversion easy).

avg 5 GPH over a 2 hour period = 10 gallons used

it's obviously not automatic, but it's fast to do.
on a boat this would be very inaccurate as we deal in large values and large variations in consumption.

ie can be trolling at 1.5 GPH and cruise at 5 GPH and open throttle up to 13 GPH, averaging such values over time would give huge variations depending on time spent at each speed.
robertisaar
Author of Defs
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Location: Camden, MI

Post by robertisaar »

i do this constantly for fuel economy calcs...

take trip duration, convert it into decimal format of hours, multiply it by average GPH over the entire trip, then you have fuel used.

if you were to mess with something that has an accurate vehicle speed signal as well, then you can also calculate average speed in the same fashion and come up with total distance traveled.

using those two values(fuel used, distance traveled), you generate a very accurate MPG value, within a few percent of error.
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