Garmin GMI20 Guage Fuel accuracy

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Quote Originally Posted by Moonlighter View Post
Guys, I have done a lot of research and have lots of practical exprience on the Suzuki NMEA 2000 networks.

Firstly, the Suzuki interface cable automatically detects the engine year and hp it is connected to and has done for several years now.

No configuring of the interface is required any more, Scottar.

But yes, the intface can be calibrated using SUZUKI or Navico head units to improve fuel use accuracy, if necessary.

One thing many people dont know is that the Suzuki interface has a inbuilt storage/memory module, kind of like flash memory, that holds all the fuel used and related data. When used with Lowrance or Suzuki engine data displays or MFD's, those displays automatically select the Suzuki interface as the network data source for all fuel related info. They don't have their own on-board fuel data storage module. So the system works nicely.

Now, the Garmin displays add a complexity to the network. You see, the Garmin displays, unlike most Lowrance/Simrad, have their own on-board fuel data storage module. So when they get put onto a Suzuki network, they auto-select their own internal fuel data memory as the source of fuel data. What does this mean? It means that the fuel used/remaining information that is displayed on the Garmin screen is sourced from the Garmin itself, not from the Suzuki interface..... Plus, the network now has potential data conflicts due to 2 different sources for the same data.

My theory is this: the GMI-20 has a known fault where it quietly freezes and thus fails to calculate and record fuel useage. Therefore the actual fuel used and the preducted fuel used from the Garmin display do not match and the Garmin therefore significantly under-reports the amount used.

My suggested solution for those with Garmin GMI displays is to go into the Garmin displays network menu and find the network data sources menu. Find the current data source for all the fuel data items that you use, and change them from the Garmin (itself) and reset them to source their data from the Suzuki interface. The Garmin manual will tell you how to select data sources, i know how to do it on Lowrance or Simrad but am not that familiar with the procedure on Garmin displays, but it definitely will be there.

By using this approach, i believe that it wont matter if the GMI freezes - when it comes back on, it will look for fuel data from the Suzuki interface and this WILL be accurate because the interface is always is working whenever the engine is turned on and the network is powered. So, it will display the fuel used and remaining data that it finds from the interface.

Bingo, accurate fuel data displayed at all times! (Subject only to the possible need to calibrate the interface if it is a bit out)

Anyone like to volunteer to give this proposed solution a try? I am pretty confident that it will work. And i cant see any downside or problem that trying it might cause. But we will only know for sure if this is tested in the field.
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