Garmin GMI10 Fuel Flow Calibration - Is It Possible?

[Back In Black]

I'm all over it Moonlighter, I hope
What I do when using the bladder is have the system set to full fuel tank capacity Eg: 460 litres.
I take note of how many litres I put in the bladder Eg: 100 litres
Then run on the bladder first to get rid of that fuel and monitor my GMI10 by how much fuel I've used until I get down to near empty and wait til totally drained.
Note: I never run the bladder nearly dry if I know I'll be close to any tight areas or crossing a bar.
I always calculate how much fuel I'll intend on burning to where I'm going when filling the bladder.
Once emptied I then reset the GMI10 to fill tank level back to full Eg: 460 and go from there.

Popped into Jeffers this arvo and had a chat to Keith & Ben about the 1.9% to 8.39% discrepancy.
They think that it could be a dodgy T piece connector or because I only have one power source connected into the backbone system causing it to drop in and out occassionally.
I got another power cable and will connect it to see what happens.
They also loaned me a unit and I'll reset the discrepancy to 2% for now as that is what I always thought it was.
Will have to wait and see what happens from there

I told you Rob it was probably a dodgy T piece connector

[Moejoes]

No probs Lee

Gday Rob, I am keen to hear how this pans out because I have had this same discrepancy of about 8% from new. I also run 2 power leads to my nmea network. I will be keen to talk with you about results.

Good luck
Lee


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[Moejoes]

But I thought it was those formulas you worked out for me

I told you Rob it was probably a dodgy T piece connector

[Jason Green]

But I thought it was those formulas you worked out for me

I think the broom stick handle might be the best option
If you get a straw one you can even leave the head on and use it for cleaning or as a paddle in case you run out of fuel [emoji23]


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[Moejoes]

Or I could use it to fly away on

I think the broom stick handle might be the best option
If you get a straw one you can even leave the head on and use it for cleaning or as a paddle in case you run out of fuel [emoji23]


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[Moonlighter]

I'm all over it Moonlighter, I hope
What I do when using the bladder is have the system set to full fuel tank capacity Eg: 460 litres.
I take note of how many litres I put in the bladder Eg: 100 litres
Then run on the bladder first to get rid of that fuel and monitor my GMI10 by how much fuel I've used until I get down to near empty and wait til totally drained.
Note: I never run the bladder nearly dry if I know I'll be close to any tight areas or crossing a bar.
I always calculate how much fuel I'll intend on burning to where I'm going when filling the bladder.
Once emptied I then reset the GMI10 to fill tank level back to full Eg: 460 and go from there.

Popped into Jeffers this arvo and had a chat to Keith & Ben about the 1.9% to 8.39% discrepancy.
They think that it could be a dodgy T piece connector or because I only have one power source connected into the backbone system causing it to drop in and out occassionally.
I got another power cable and will connect it to see what happens.
They also loaned me a unit and I'll reset the discrepancy to 2% for now as that is what I always thought it was.
Will have to wait and see what happens from there

Adding an extra network power source .... a most courageous decision indeed.
Unless its one of the special dual/triple power nodes, the first rule of N2K networks is only 1 source of power active at any one time.
Be interested to hear how that works out.
If you had a dodgy T piece that was intermittently failing, I think you would notice that all engine data was missing, not just fuel. To me what you have is simply a calibration issue.
What is the procedure to reset the discrepancy to 2%?


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[Moejoes]

Been told that the one power source isn't enough if you have multiple units drawing power from the back bone.
I have about 7 items drawing power and they suggested that the single cable is only allowing say 3 amps ( Only guessing this figure ) into the back bone
One of my GMI 10's has it's own power source but the other plus everything els I have plugged into it relies on the backbone for power supply.
I will try out and see what happens.
As for calculating the 2% I'm going to work it back to 20 litres on a full tank burn.
Need to check the current readings on the GMI10 then I'll set up an excel spreadsheet with formulas to calculate back.
Should be a simple process which I'll sort out during the week.
Today is wheel bearing and brake servicing day
Will keep you posted.

Adding an extra network power source .... a most courageous decision indeed.
Unless its one of the special dual/triple power nodes, the first rule of N2K networks is only 1 source of power active at any one time.
Be interested to hear how that works out.
If you had a dodgy T piece that was intermittently failing, I think you would notice that all engine data was missing, not just fuel. To me what you have is simply a calibration issue.
What is the procedure to reset the discrepancy to 2%?


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[scottar]

Bit more complicated than that Rob. Have a bit of a read of the Maretron NMEA2000 installation guide. The calculations required take into account network length and LEN's (Load equivalency numbers). Each device in it's specs should have a LEN that is used for this. In practice though mate it is not something I have ever needed to take into account on a trailer boat - they are simply neither big or complicated enough when you look at the network design parameters (although by Tony's account, some things on Moejoe's are pretty complex) . Biggest network I have played with was an 8 tee network that did have two separate power sources but also had an isolation cable fitted - some of the network needed full time power but some only when the engines were on. If you are adding a second power lead, make sure it comes from the same supply point as the first unless there is an isolation device fitted

https://www.maretron.com/products/pd...on%20Guide.pdf

[Back In Black]

Bit more complicated than that Rob. Have a bit of a read of the Maretron NMEA2000 installation guide. The calculations required take into account network length and LEN's (Load equivalency numbers). Each device in it's specs should have a LEN that is used for this. In practice though mate it is not something I have ever needed to take into account on a trailer boat - they are simply neither big or complicated enough when you look at the network design parameters (although by Tony's account, some things on Moejoe's are pretty complex) . Biggest network I have played with was an 8 tee network that did have two separate power sources but also had an isolation cable fitted - some of the network needed full time power but some only when the engines were on. If you are adding a second power lead, make sure it comes from the same supply point as the first unless there is an isolation device fitted

https://www.maretron.com/products/pd...on%20Guide.pdf

You ever seen that damn thing Scott??

[Dignity]

Told you that you need Yammies, their gauges automatically calculate a 10% reserve.

[Back In Black]

Told you that you need Yammies, their gauges automatically calculate a 10% reserve.

Jason's going to love you, & Rob will boycott you off Moejoes......

[Dignity]

Jason's going to love you, & Rob will boycott you off Moejoes......

Nah, he'll have to teach some other mug how his towing harness works.

[Back In Black]

Nah, he'll have to teach some other mug how his towing harness works.

And we all know how hard that is.............

[Moonlighter]

Bit more complicated than that Rob. Have a bit of a read of the Maretron NMEA2000 installation guide. The calculations required take into account network length and LEN's (Load equivalency numbers). Each device in it's specs should have a LEN that is used for this. In practice though mate it is not something I have ever needed to take into account on a trailer boat - they are simply neither big or complicated enough when you look at the network design parameters (although by Tony's account, some things on Moejoe's are pretty complex) . Biggest network I have played with was an 8 tee network that did have two separate power sources but also had an isolation cable fitted - some of the network needed full time power but some only when the engines were on. If you are adding a second power lead, make sure it comes from the same supply point as the first unless there is an isolation device fitted

https://www.maretron.com/products/pd...on%20Guide.pdf

My thoughts exactly.

The splitter power leads you are referring to are made by Garmin amongst others, to allow one half of the network to be powered while the other is off. The ones I mentioned are a bit different, dual or triple power nodes that all connect thru one T piece with the aim of ensuring the network always has power when one or the other source is turned off.

I don't know what damage can be done with 2 separate power supplies, have never been brave enough to test it, but I guess we will know soon enough. Fingers crossed for you guys that it doesn't damage anything too badly!

Before you add a second power supply, your could try relocating the power supply to a T in the middle of the cluster. That is the recommended practice on larger networks in any case, and usually deals with the power drop issues.

Note that most devices on the network are not powered by it, the newer Garmin GMI-10's are, and things like GPS pucks and the like, all of which have very low power draws. Other devices like MFD's on some examples draw a tiny amount to run their N2K circuits, but not to run their normal functions.

Even the Suzuki engine interfaces are not powered by the bus, they are powered from their connection to the engine, despite what some people will try to tell you.

So not sure what the 7 devices might be that are drawing so much power from the network that a second supply is needed in this case?

Anyway, let us know if you need further assistance. I still think you will need to calibrate, it is a pretty common thing to have to do.



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[scottar]

I don't know what damage can be done with 2 separate power supplies, have never been brave enough to test it, but I guess we will know soon enough. Fingers crossed for you guys that it doesn't damage anything too badly!

Worst case scenario - lots of smoke possibly some flames and an insurance claim in the event of a negative supply failure for one of the power supplies. Provided all power supply inputs originate at the same battery this should not be an issue. Where it becomes a problem is if one negative from one battery and one from another battery in parallel are connected to the bus and then one of the supply negative connections fails thus leaving the bus negative to be the only "tiebar" connection for negative. Positive power feeds are typically fused and will thus "disconnect" in a high current flow situation - negatives aren't typically and thus get real hot real quick unless there is isolation within the bus.