Optimum fuel usage help

[Phlorida]

To date I have been operating my 5.7L just below where I believe my secondaries kick in and hoped that I had picked a sweet spot. I just purchased a fuel flow meter that I am hoping to install this week and it occured to me that I'm not sure that I know what to do with the data.

My "best" fuel usage rate is idle and my "worst" fuel usage rate is WOT - I don't need a gauge for that. Is there an algorithm to use with my collected fuel flow data to show me where my optimum usage rate is?

If this has been covered in another thread, apologies and please point me to it.

 

[docofthebay]

Your best data on fuel usage will be miles per gallon. You will have to figure it yourself unless your new fuel flow device has a gps interface. If not you can do an estimate on fly by dividing your current gallons per hour ( this is the real time data output from a fuel flow meter- gallons per hour) figure into the current miles per hour you are traveling. If you will determine average mpg per every 100 rpm step ( and then record it somewhere easily accessible), you will not only find the sweet spot which will be the best cruise speed, but now also have a data reference to how your boat performs now and for comparison in the future to know when you are having engine difficulties, prop problems or dirty bottom affecting performance

 

[jrock1062]

I have a Fuel flow meter attached to my Garmin via the Nema 2000 system, the information that is displayed is, GPH, MPG total gallons on board how many miles I can travel under the current conditions with the gas I have on board. All of these numbers change as you slow down, speed up, or conditions change. I do not have a big boat but having the fuel flow meter has saved me money,after having one I would never own a boat without one

 

[Phlorida]

I bought a Garmin GFS10 to interface with CANet to a Garmin 525S. That should provide me with the the MPG data referenced. I guess that it is as simple as that - MPG, even thought the changes will be in the second decimal place.

 

[Jimmy Buoy]

It isn't always as predictable as you might think. My last boat had twin 5.7 V-Drives and after getting fuel flow meters, I found that 4200 RPM was my BEST MPG. I had been babying it for two seasons, running it at 3000-3200 RPM thinking I was saving fuel.

The only problem was the thought of engine wear that went along with continual 4200 RPM running, so I chose to run at a more easy going 3500 RPM. The boat planed at a more level attitude at higher speeds making much less wake. Less wake is usually less fuel.

By the way, my current boat does not and will not have fuel flow meters. It was just too depressing to see just how much fuel was being used with each outing!

 

[RollerCoastr]

I guess that it is as simple as that - MPG, even thought the changes will be in the second decimal place.

That's true, but unfortunately, Garmin programmers decided that we all we'd be interested in is MPG to the tenth. :smt021 I have submitted a feature request to add the second decimal place. I'm really hoping they listen. (and it couldn't hurt if more people requested it!)

http://www8.garmin.com/contactUs/ideas/#container-form

In the meantime, the data IS there - but you'll need a calculator to get it. I find the bar graphs on my 5212 too hard to read to be a good reference, but the "range" figure can also help tell you when you're most efficient.