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Fuel Flow Data Problem - CAT 8.7 to Maretron to Garmin
My boat came with CAT 8.7s. Upon delivery, I discovered that the fuel flow and totalization was 8-12% inaccurate. Examination of the system revealed that the fuel data was not transduced, but reported by CAT's ECM on a scheduled basis based upon load and RPM. This data, along with other data, is sent to a Maretron unit where it is converted into packets and put onto the NMEA bus to be sent up to the Garmin. I have Garmin 8617s.
Since I intended to utilize the boat for longer missions, I wanted accurate data. I asked my service center (owned by the boat builder) to scope and install a Flo Scan system - after carefully mapping all the requirements and potential issues. However....
They cannot seem to get rid of the CAT flow data at the Garmin. In theory, there should be at least one of three solutions - turn the data stream off at the CAT (I can't imagine that CAT would force all users to utilize scheduled rather than transduced data), re-arrange the Maretron configuration to exclude the data or divert the data into different data fields at the Garmin, where it could be ignored - something, right ?
In any case, I'm concerned that the manufacturer has hit a dead end, so I need some help resolving this. The Flo Scan system is installed and operational, although the best we've been able to do is add data fields in the Garmin for flow. Totalization, range and economy stats are all distorted because the Garmin sees both the CAT and Flo Scan data, so everything is doubled.
Any ideas ?
I'm pretty sure you're using a Maretron J2K100 to convert from the Cat's J1939 to NMEA 2000. Assuming that's correct I don't think you're going to be able to stop the engine from sending fuel flow data on the J1939 network, but you might be able to stop the J2K100 from sending fuel flow data. I just looked through the manual for the J2K100 and I don't see a way to disable the transmission of a single data element. The issue is that most of the engine data is transmitted in a single engine update PGN (127489) so we need to find a way to tell the J2K100 to stop grabbing fuel data from J1939 and inserting it into the 127489 data packet. I would reach out to Maretron and ask if that's possible.
In the meantime, it might not be pretty but I think the best way to handle this would be to set the Flo Scan's output to a different engine ID than the J2K100. You will end up with two engines showing up instead of one. Say for example you leave the J2K100 at engine id 0 and the Flo Scan at engine id 1. Then you will know to ignore any fuel data from engine 0 and only pay attention to engine 1.
The only other option I can think of would be to use something like a Yacht Devices NMEA 2000 bridge and write a small program to modify the data in the 127489 pgn coming from the J2K100 to blank out the fuel data. I've never done this before but believe it would be possible. And, in full disclosure, I own the Yacht Devices US distributor ( https://www.yachtdevicesus.com).
We have the flo scan flow data assigned to data fields in the Garmin display. However, since we can't turn off the scheduled data from CAT, the Garmin sees both sets of data (2 fuel flows for each of the 2 engines), which makes for distorted totalization, fuel remaining, nm/gal, and range calculations.
One thing you didn't mention is getting the Garmin to ignore the CAT data. Any idea how to run this question down ?
I'll look at these other suggestions. Thank you
If I was certain the bridge would strip on the flow data from the 127489 packet and leave the rest of the data intact, it would seem a no-brainer. Who would I get to write the code ?
@jimthompson I've talked to Yacht Devices Limited and they confirm the YDNB bridge would be able to do exactly what you need. Basically what you will need to do is build a second small NMEA 2000 network with your Floscan and Maretron J2K100 on that network. The program running on the bridge will then intercept the messages, strip fuel info from the Maretron message and insert information from the Floscan.
Feel free to send an email to the Yacht Devices US sales box for more info: [email protected]
I've sent an inquiry to them.
The NMEA bridge with some expert programming, both from Yacht Devices fixed the problem that Cat, Maretron and Garmin said couldn’t be solved.
The guys at Hinckley were impressed.
This was an interesting exercise and I'm really pleased with how it came out. The program that Yacht Devices wrote takes the engine PGNs from the Maretron J2K100s, it strips out the fuel flow information in the packets and replaces it with data from the Flo Scans. So now, Jim's MFDs get engine packets with all the information he's looking for and the inaccurate data from the engine ECUs removed.
This works by putting the J2K100s and Flo Scans on their own NMEA 2000 network. The bridge then connects the engine data NMEA 2000 network to the rest of the boat's NMEA 2000 network. But, before it sends the data it does the substitution to get just the data Jim is looking for.