Affordable fuel usage meter

[Simi 60]

All of the flow meters shown in this thread have just one sensor. Diesels need two which was mentioned briefly a few posts back. You need one to measure total diesel flow and subtract the return diesel flow from another to get diesel burned by the engine.


David

I didn't see the sense in posting two of the same picture but I did say two would be needed.

 

[Simi 60]

My solution is time.......Fuel used, and hours run. Over a 4 year period I have an excellent reference of Average fuel used per hour.

Average fuel burn is relatively pointless for passage making where there will be 1000s of miles between reliable fuel sources.
I want to know what range I can get at 6.5 knots vs 7.5 vs 8.5 vs 9.5 knots.
12 litres/ hour vs 35 litres/hour
The difference in range will be 1000's of miles

I don't need any more than that along with some very accurate analog gauges on the top of my tanks... Cost is $00

Your cost could well be many hours cruising at an inefficient speed
Probably doesn't matter if you don't do many miles away from a fuel dock and have cheap diesel

 

[Larry M]

I look at fuel monitoring systems more than just gph or fuel used. We have a FlowScan system and during the fuel tank replacement/engine room rebuild, one of the sensors was damaged so the system wasn’t working. While breaking in the rebuild, we had a fuel leak in the return line at an injector and came close to damaging the rebuilt engine. If the FlowScan had been working, it would have helped us find the problem sooner. The system has also given us an indication of how clean the bottom and or running gear is.

 

[jimisbell]

Geeezz, I thought I was OCD, (BTW, that should be CDO so the letters are in the proper alphabetical order.) but all I do is watch the fuel gauge and get fuel when I need it......AND I DONT run faster than 7 knots. I know my range and I dont exceed it.


Kind of like my car. Do you worry about the gallons per hour on your car???? You instinctively know that if you go fast the fuel will go fast, if you go slow, you can drive further, and you watch the gauge. Simple.

 

[Simi 60]

Geeezz, I thought I was OCD, (BTW, that should be CDO so the letters are in the proper alphabetical order.) but all I do is watch the fuel gauge and get fuel when I need it......AND I DONT run faster than 7 knots. I know my range and I dont exceed it..

Great for you.
As yet we haven't filled our 2000 gallon tanks and ran them down to see what we can get.
We can theorize, we can guess, but are not sure.
When we find out we will know and won't have a use for fuel usage meters any longer

Kind of like my car. Do you worry about the gallons per hour on your car???? You instinctively know that if you go fast the fuel will go fast, if you go slow, you can drive further, and you watch the gauge. Simple

You are right, it is simple in a car.
For most of your driving you are close to petrol stations and if you run out its no drama as you simply pull to the side of the road and wait for someone to turn up with some more or a tow.

Different story to if we are on passage with several thousand miles between fuel stops and no one to bail you out.
Then you might be a bit more concerned about your sweet spot for mpg, especially when our fuel costs almost 2x what you pay.

 

[psneeld]

Cant compare to a car...no set and drift varying your speed/distance over ground per fuel use.

Accurate fuel consumption numbers allow you to close in on a reserve that is viable, not some guess.

Sure you can live without accurate numbers.... like you can without all kinds of safety equipment...till that one time, for whatever reason, it comes in handy.

I spent a career betting my life on accurate fuel numbers...as the tech got better...I could relax a bit more and more.

For a few dollars, I would love to have pretty accurate fuel info.....but because my boating doesnt require accurate numbers very often, a high price tag is what is stopping me from adding a system.

 

[f508]

It looks like you are going to tap into the fuel lines to add these meters. I wonder if you could just use a 5 gallon bucket with the return running back to the bucket and a known quantity of fuel, say 1 or 2 gallons, marked on the bucket. After you time the net burn off of a couple of gallons at various power settings, put everything back the way it was.

I noted when I fueled my boat for the 1st time that my tanks hold 12 gallons per inch on the sight gauges until I get to the last 50 gallons where the tanks taper and hold 6 gallons per inch. If you calibrated your sight gauges at your next refueling I think you could reach a confidence level equivalent to these gauges of unknown accuracy.

BTW, my engines (1983 Lehmans) burn very close to the fuel flows in the manual. So considering that I only cruise at 7 knots, and therefore am highly vulnerable to tides and currents, I wouldn't plan a voyage with less than a 25-30% reserve. This inclination on my part to hold a large reserve makes it unnecessary to have a super accurate fuel flow estimate.

But it sounds like a fun project.

 

[Simi 60]

From what i understand Cummins pt fuel system shifts a lot of fuel.
Your 5 gallon bucket would be drained and the return overflowing very fast.

Tapping into the fuel line and returning it to standard is pretty simple.
Less effort than dicking around with extra small tanks and buckets IMHO.

 

[Wxx3]

My estimates on fuel consumption over time are as accurate as flow meters. However it need to have accurate sight tubes and it's not instantaneous.

 

[Lou_tribal]

I mistaken myself and reading posts now understand the goal of what Simi want to achieve. If I was to prepare a long range crossing I would do the same in order to get measurement as accurate as possible. Also I guess that it is easier to get measurement of a 200 gal tank than of a 2k gal tank, at least you don't need to burn 500 gal to get a reading

L

 

[BandB]

The killer for Floscan was that almost all modern engines come from the manufacturer with fuel monitoring as part of their electronics package.

 

[CaptTom]

The killer for Floscan was that almost all modern engines come from the manufacturer with fuel monitoring as part of their electronics package.

This is very true. The market for flow meters is shrinking. Corporations only like to grow.

But FloScan's exit opens up this smaller, but still significant, market for innovation.

If someone can sell the sensor, computer and display on line for $40, how much more can it cost for a computer that counts usage from two sensors and puts the difference out on a NMEA bus?

 

[Conall63]

The engine manufacturer can provide you with a chart showing fuel burn at various RPM.



I use a flow meter on my transfer pump to measure exactly how much fuel I've used. When I compare the measured burn against the performance chart, the chart is always within a gallon or two of the measured rate on a 10 hour run.


Conall

 

[DavidM]

This is very true. The market for flow meters is shrinking. Corporations only like to grow.

But FloScan's exit opens up this smaller, but still significant, market for innovation.

If someone can sell the sensor, computer and display on line for $40, how much more can it cost for a computer that counts usage from two sensors and puts the difference out on a NMEA bus?

The Chinese can often sell something for 1/4 of what an equivalent American product sells for. It is not just low manufacturing costs because many "American" products are actually built in China but to American designs, quality management, distribution and sales.

Purely Chinese products do it by reducing those indirect costs. Sometimes it works and sometimes it doesn't. I bought a $40 "Drok" battery monitor which is roughly equivalent to a $200 Victron or Xantrex monitor. But it came with indecipherable Changlish installation instructions. Fortunately it was simple enough to figure out since i had previously installed several Xantrex monitors. So far it works.

I have no doubt that the Chinese could sell a diesel fuel flow monitor as described above for under $100. Would it work as well as a $500+ Flowsan or Maretron system? I doubt it because there a a few specific diesel flow measuring issues that the Chinese probably haven't dealt with- pulsing fuel flow being one of them.

David

 

[RT Firefly]

Greetings,
Mr. 60. I can appreciate you don't want to be "dicking around" with spare or extra tanks so my idea is out (post #16). I also agree with Mr. CT (post #42)...How hard can it be to provide 2 sensors and have some sort of software do the math to give you a usage figure?


Sensor A (feed) minus sensor B (return) = fuel usage.


Mr. dj. "...issues that the Chinese probably haven't dealt with." I very highly doubt that. IF there's even 1$ to be made, there will be someone (Chinese businessman) who will sell it. Granted, a Chinese unit may not perform as well as a name brand unit but then again, it may.

 

[O C Diver]

When I replaced the engine in my trawler during my refit, I considered a day tank of around 50 gallons for measuring fuel burn and having a clean tank of fuel while underway (fuel would be polished going into the day tank). During the install, the dealer explained the fuel monitoring in the gauge package, which made the day tank less necessary. A day tank in your situation might work very well. Mine was going to be 25" tall with a protected sight glass on the side. Each inch would be 2 gallons.

Ted

 

[Heron]

My estimates on fuel consumption over time are as accurate as flow meters. However it need to have accurate sight tubes and it's not instantaneous.

And remember, Richard has crossed Oceans on Dauntless......

 

[Simi 60]

And remember, Richard has crossed Oceans on Dauntless......

And remember, Richard has accurate sight tubes.

I have sight tubes, I have marked them using maths, but they are shaped tanks and I failed maths at school so they may not be accurate.

The only way to get them truly accurate would be to drain the 3500 litres (at a guess) we have now and refill with 7000 litres in 500 litre increments marking as we fill.

 

[FF]

"The engine manufacturer can provide you with a chart showing fuel burn at various RPM."

Yes , but only if the load is known .

A rough guess, like a theoretical boat , theoretical prop graph and theoretical load is a very crude tool.

Instead of a proper fuel or BMEP chart these theoretical guesstimates are all that is released from many sellers.

Most boat engines are marinizations of an engine , car , tractor or truck,and enough digging on the engine mfg site might find useful information .

Dig thru the pump or gen set info , if published.

 

[boomerang]

This is something I plan to try, seems reasonable priced haven’t heard any real time reviews yet.

Interactio | Optio Fuel Flow Monitor


Ron

Ron, the link you posted for those Interactio flow sensors has me interested. I like the wireless concept. They're a little pricey but so is everything else I have ever bought for a boat. I'm thinking about giving the setup a whirl!
Thanks again for posting the link.
Shawn

 

[jimisbell]

"The engine manufacturer can provide you with a chart showing fuel burn at various RPM."

Yes , but only if the load is known .




This fulfills the OPs needs. He is looking for the "sweet spot" in RPM range. It will always be at the same RPM regardless of load.

 

[Insequent]

I have a Floscan that I could consider selling. It came off a Cummins VT555. The unit is Model 6520 (range 20gph), and the sensor is model 231.

Now, the first strange thing is that the mechanic who removed it said there was only one sensor, and he did look for a second one! Normally a diesel will require two sensors as noted above. I don't know where it was fitted. But it did give steady and apparently accurate readings.

The 555 has a high fuel return flow, over 5x engine consumption from memory. Perhaps engine consumption was a constant proportion of the total fuel flow for that engine/pump?

The other strange thing is AFAIK that particular sensor is for petrol (gas) flow measurement. But as I said, it worked!

Simi, perhaps you could contact the Australian Floscan guy to check whether you would be able to use it. I won't be home for at least a month, and then I would need to try and find it in my shed....

 

[markpierce]

Meanwhile, I' m riveted on the instant of readings miles-per-gallon in my automobile. My 2018 Ford Edge gets a one or two miles a gallon less than my former 2014 Edge.

 

[markpierce]

I have a Floscan that I could consider selling. It came off a Cummins VT555.
...

My Floscan only goes up to 10 GPH, but maximum consumption is only 4 GPH. Don't see the need for a higher range for hull-speed (and slower) trawlers.

 

[Insequent]

My Floscan only goes up to 10 GPH, but maximum consumption is only 4 GPH. Don't see the need for a higher range for hull-speed (and slower) trawlers.

You should match the gauge to the engines. My Cummins could drink 17gph at WOT, so the gauge I had was right-sized.

But I did not want to pay for that kind of fuel use, so when I repowered I installed smaller HP engines.

 

[sdowney717]

I would love to advance past the measured sight glass and guesstimate method to work out our fuel burn but am not prepared to spend $1000 to do it as once I have the numbers I would not use it again.
But I would spend $100

After my success getting a $20 engine water/oil temp alarm on eBay I thought I would try the same for fuel and found these.

This one has 1/2inch fittings rated for diesel for $70

This one has 1/2inch fittings rated for diesel for $55

I would need one on the low pressure side of fuel to engine
And one on the fuel return to tank.
Both easily accessible and fitted on ours.

At start of run set both to zero
Run for an hour at 1000rpm
Subtract one reading from the other and that's usage at that speed

Repeat for 1050, 1100, 1150 etc

Thoughts?

Same on for $50 here. Since it uses batteries I don't like it.
https://www.aliexpress.com/item/201...7115e11&transAbTest=ae803_4&priceBeautifyAB=0

 

[sdowney717]

https://www.aliexpress.com/item/1pc...7115e11&transAbTest=ae803_4&priceBeautifyAB=0

$36 for the same one you linked at $55

A China manufacturer-seller can use Ebay and Amazon which seems to be more expensive or Allied Express which seems to be cheaper.

 

[CEC]

I'm not sure of the quantities of the return per gallon on your motors but if its around 10th or 8th of a gallon or so per gallon burned that would be a good reserve in terms of tide, wind, and current. You could just use one and get a feel for your range at different RPM's leaving the return as the reserve. Rather then trying to run in all directions of current, tide, and wind to try and get an average with two sensors.


If using a spare isolated 5-10gal tank with the return going to it you would only need one sensor to quickly determine the actual MPG at a given RPM including the return - minus the other factors.


If I do this I would not leave the cheapo meters inline. I would just use to figure things out then remove, so the batteries are non issue for me. The hard part is figuring out burn @ RPM in all loads and conditions, so Id probably just ignore the return factor for my boat.

 

[Aquabelle]

On many high output diesels the return volumes are greater than the burn volumes. At $36 for an additional sensor, what's the issue ?

 

[Ski in NC]

Keep in mind that the accuracy of these flowmeters falls badly when at low flow rates. Meters often have accuracy of 2-5% of rated flow rate, but get down to 10% of max flow rate and now accuracy is much worse. Combine with that you are subtracting two numbers, close together in value, yet each inaccurate to some degree, and total error compounds badly.

So if you size both meters for max flow, then go to low cruise, numbers then can be garbage. Not good enough to make an accurate speed vs burn rate chart.