Fuel flow meter on my Diesel?

Hi guys.
Just wondering if anyone has installed a fuel-flow meter in their fuel line to measure and monitor fuel flow while running their engine(s)

I would like to be able to see what my flow-rate is based on throttle settings in order to determine optimal power/thrust settings.

Has anyone tried this?
What fuel flow meters are out there that are diesel compatible?

I am aware that the flow rate may be questionable if your diesel injectors dump a lot of fuel into the return line.

Curious all the same.
Thanks.

A proper setup for a diesel will use 2 sensors per engine. One in the feed line, one in the return. That way it gives accurate data regardless of how much return flow you have.

www.floscan.com › html › blue › dieselmodels.php

Has been creating what you need for probably 12 century.

Many choices on E bay if you want to roll your own.

Not all engines have enough return volume to need 2 sensors.

FF said:

www.floscan.com › html › blue › dieselmodels.php

Has been creating what you need for probably 12 century.

Many choices on E bay if you want to roll your own.

Not all engines have enough return volume to need 2 sensors.

Click to expand...

Unfortunately Floscan went out of business a few years ago. They did get resurrected (new site is https://floscaninc.com/), but I haven't found any place that actually has and will sell any of their marine products, so I'm not sure they're in current production (other than maybe calling them to order).

I had a Flo Scan meter on Possum. It was very useful. As I recall it not only told me what the current fuel usage was but total fuel used since I last reset it.

I was very surprised when Flo Scan went out of business. They made a great product and provided excellent customer service.

HopCar said:

I had a Flo Scan meter on Possum. It was very useful. As I recall it not only told me what the current fuel usage was but total fuel used since I last reset it.

I was very surprised when Flo Scan went out of business. They made a great product and provided excellent customer service.

Click to expand...

At least for the marine market, I think the proliferation of electronically controlled engines that can provide fuel flow data without add-ons destroyed a large part of their market. There are only so many users of older, non-electronic engines out there that don't already have flow meters and also want to add them. That said, I'd love to add meters to my boat, but there's just no cheap way to do it.

Think they're back in business... good thing as they are about the only one that makes these transducers.


I've installed several in aircraft (very similar) and they are very accurate (in the .5% range when set up properly.



The hard thing is emptying the tanks to determine tank quantity. Ya have to tell the unit how much fuel is 1/4, 1/2, 3/4 and full. And you can put in an amount you never go below. That calibration is a PITA. I suppose one could do it when the tanks are as close to empty as you can get them, pump out the rest and fill with a known quantity.


Personally, I'd be happy with the flow part and skip the quantity, as I have more than enough and with my travels, never an issue. But would like to tweak MPG and spend more money on beer.

FF said:

www.floscan.com › html › blue › dieselmodels.php

Has been creating what you need for probably 12 century.

Many choices on E bay if you want to roll your own.

Not all engines have enough return volume to need 2 sensors.

Click to expand...

Thanks!

rslifkin said:

Unfortunately Floscan went out of business a few years ago. They did get resurrected (new site is https://floscaninc.com/), but I haven't found any place that actually has and will sell any of their marine products, so I'm not sure they're in current production (other than maybe calling them to order).

Click to expand...

Also Thanks!

You might also look at Maretron as they offer fuel flow meters. I have no experience with them so no advice either.

https://navstore.com/engine-systems/fuel/fuel-flow-and-monitoring/


I have monitored my fuel use by tank fills vs hours run and have a reasonably accurate idea of use based on those hours. Took some time but it is good enough.

My boat has a single 2003 Cummins 6CTA engine. I had Maretron fuel flow sensors installed - it takes two per engine. I like having the data to fine-tune my progress through tidal currents.

The data displays on my Garmin chartplotters and on the pre-existing Maretron screen.

I have Maretron fuel flow sensors as well as their tank level monitors. Probably one of the best things I added to the boat. Finding my optimal burn (especially on longer trips) has already paid for them. I have twin CAT 3208TA (375hp).
You will need 2 sensors per engine as well as the module that reads the data and then allows for the connection into the N2K network. I have all my fuel data displayed on my Axioms now... LOVE THEM!!!
While I was upgrading, I also had a hydraulic shop custom make all new fuel lines for me with nice crimped on connections...

The one "downside", you need to also buy their programming device ~$400, which depending on what you do, may only need to be used once. So if you can find a used one or borrow one...

C lectric said:

You might also look at Maretron as they offer fuel flow meters. I have no experience with them so no advice either.

https://navstore.com/engine-systems/fuel/fuel-flow-and-monitoring/


I have monitored my fuel use by tank fills vs hours run and have a reasonably accurate idea of use based on those hours. Took some time but it is good enough.

Click to expand...

That is the tried-and-true method from everyone I talked to who was able to tell me their approximate fuel consumption per hour.

But...

I anticipate it is a tedious process and you have to be very precise in your records. It also requires a full tank every time so you can record the fuel that went into the tank and compare against your run-records for everything that led up to filling the tank.
I was consigned to this method but I really would prefer to have a fuel-flow sensor instead

Scottwb96 said:

I have Maretron fuel flow sensors as well as their tank level monitors. Probably one of the best things I added to the boat. Finding my optimal burn (especially on longer trips) has already paid for them. I have twin CAT 3208TA (375hp).
You will need 2 sensors per engine as well as the module that reads the data and then allows for the connection into the N2K network. I have all my fuel data displayed on my Axioms now... LOVE THEM!!!
While I was upgrading, I also had a hydraulic shop custom make all new fuel lines for me with nice crimped on connections...

The one "downside", you need to also buy their programming device ~$400, which depending on what you do, may only need to be used once. So if you can find a used one or borrow one...

Click to expand...

YEAH!!!!

Now that's what I am talking about!!!

Calibrating a Flow Scan does not require an empty tank , it is quite simple.

Start with a full tank and use a guesstimate to start the unit.

On the next fill write down the gal installed and compare it to the gauge gallons used.

Reset the gal used , and do the reset 3 or 4 times as you travel.

On many occasions er kept a running log of gal filled and added all up for a longer reset and more accuracy.

On a 100G tank we would know the amount to add within a couple of gal.

After 6000 miles of loop it was really accurate!. The reset was protected with a key switch to maintain accuracy.

On a 100G tank we would know the amount to add within a couple of gal.

Click to expand...

I could do that for my Albin with the single FL 120 just by using the tank gauge.

Just curious, what engine(s) is the OP using in his boat?

Just MY opinion, but with my Albin a fuel flow system would have been useless in practicality. With twin 180 gallon fuel tanks and using my "estimated" 1.75 gallons per hour which was calculated fairly quickly, it was very repeatable assuming "normal" cruising patterns. That included generator use, idleing while waiting for locks, anchoring, etc.
It was repeatable for the 14 seasons I owned the boat.
And if it changed to 1.8 or 1.6 it really was of no consequence.

jleonard said:

I could do that for my Albin with the single FL 120 just by using the tank gauge.

Click to expand...

Same here. Over the course of the last 2 seasons, my estimate for how much fuel it would take to fill the tanks has never been off by more than ~10 gallons going just off the gauges. As long as you have good working gauges and learn how their readings line up to actual fuel in tank (being that most tanks aren't perfect rectangles), they're plenty good for knowing how much fuel you have and need.



That said, if it weren't so damn expensive, I'd still love flow meters for a better accounting of fuel burn vs speed while running. Especially when something forces us to run at a speed that isn't one of our typical cruising speeds.

Is not the Flowscan or Maretron fuel flow sensors the same technology my 2007 Cummins QSB has? I find myself cruising by GPH rather than MPH or KPH.

HeadedToTexas said:

Is not the Flowscan or Maretron fuel flow sensors the same technology my 2007 Cummins QSB has? I find myself cruising by GPH rather than MPH or KPH.

Click to expand...

More or less. In the case of your engine, the computer knows what the injectors flow and how much time it has them open, so it knows how much fuel the engine is burning without needing additional sensors.

There are flow meters that are not boat specific, just make sure it can handle diesel. The ones that I've used have a AA battery and are completely self-contained. Not even necessary to connect to 12V. The gauges look cheasy next to nautical gauges, but that really doesn't matter for most people as there is no need to permanently mount. You don't need to stare at the gauge constantly. Basically, you need to get the information one time and record it (unless you are also using it as a super accurate fuel gauge and need to know when you have seven liters remaining in the tank).

Install the meter and create a graph showing that X flow rate at X rpm produces X speed. No need to permantly mount the gauge at the helm. Put the gauge out of the way in the ER or remove the whole thing. It might be frustrating for the OCD folks who want to make sure that their flow rate hasn't changed since last checked 30 seconds ago. The last one I bought was under $75. It's in the garage somewhere.

rslifkin said:

More or less. In the case of your engine, the computer knows what the injectors flow and how much time it has them open, so it knows how much fuel the engine is burning without needing additional sensors.

Click to expand...

So the QSB system calculates fuel use rather than measures it?

HeadedToTexas said:

So the QSB system calculates fuel use rather than measures it?

Click to expand...

I'm not 100% sure on that, but most likely, yes. I'm not sure I've seen any actual flow meter in place on any electronically controlled engine (marine or otherwise). Keep in mind, it knows enough to calculate quite accurately, so a flow meter in the lines (unless it's a very good one and very well calibrated) is not likely to be any more accurate.

HeadedToTexas said:

So the QSB system calculates fuel use rather than measures it?

Click to expand...

Probably yes. That's how the system works on my tier 2 John Deere. On my 135 HP engine the consumption calculation is touted to be within a tenth of a GPH (for a 7 GPH maximum consumption engine).

Ted

Roger that.

rslifkin said:

That said, if it weren't so damn expensive, I'd still love flow meters for a better accounting of fuel burn vs speed while running.

Click to expand...

https://www.futurlec.com/sensor/flowfuel30l0.shtml

Also available with the gauge and wiring for about $60. Not damn expensive.

I use one of these on my 50HP outboard with an 87 liter tank, not so much for fuel economy. It can show liters per hour (even down to .2 liters per hour when at idle) which is fine, but it's main value for me is that it is way more accurate than a flopping needle on the fuel gauge when the tank gets low.

If a monitor saves you $100 a year in fuel, but costs $700 for the kit, it's a hard sell. If it costs less than $100, then it's a reasonable investment. That's the theory that I found online as why the several companies that made smaller "nautical versions" stopped making them. I don't have one on my 80hp Lehman right now for that reason. Whether I'm burning .9 gph or 1.1 gph isn't that important. If I had two engines each burning 8 gph (as the linked sensor can read), I might think about creating a fuel burn graph.

As to return flow on some diesels, I'm not sure that is all that important. I would guess that the return flow is linear, meaning that the injector pump returns twice as much fuel at 2,200 rpm as it does at 1,100 rpm. One could still graph relative fuel usage per speed/rpm and find the sweet spot (or the sour spots) without actually knowing the exact amount of fuel consumed.

Marco Flamingo said:

https://www.futurlec.com/sensor/flowfuel30l0.shtml



Also available with the gauge and wiring for about $60. Not damn expensive.



I use one of these on my 50HP outboard with an 87 liter tank, not so much for fuel economy. It can show liters per hour (even down to .2 liters per hour when at idle) which is fine, but it's main value for me is that it is way more accurate than a flopping needle on the fuel gauge when the tank gets low.



If a monitor saves you $100 a year in fuel, but costs $700 for the kit, it's a hard sell. If it costs less than $100, then it's a reasonable investment. That's the theory that I found online as why the several companies that made smaller "nautical versions" stopped making them. I don't have one on my 80hp Lehman right now for that reason. Whether I'm burning .9 gph or 1.1 gph isn't that important. If I had two engines each burning 8 gph (as the linked sensor can read), I might think about creating a fuel burn graph.



As to return flow on some diesels, I'm not sure that is all that important. I would guess that the return flow is linear, meaning that the injector pump returns twice as much fuel at 2,200 rpm as it does at 1,100 rpm. One could still graph relative fuel usage per speed/rpm and find the sweet spot (or the sour spots) without actually knowing the exact amount of fuel consumed.

Click to expand...

It is impossible to make any assumptions as to return flow in general. Detroits return gallons per hour. A Lehman 120 returns ounces, if any.

Marco Flamingo said:

https://www.futurlec.com/sensor/flowfuel30l0.shtml

Also available with the gauge and wiring for about $60. Not damn expensive.

I use one of these on my 50HP outboard with an 87 liter tank, not so much for fuel economy. It can show liters per hour (even down to .2 liters per hour when at idle) which is fine, but it's main value for me is that it is way more accurate than a flopping needle on the fuel gauge when the tank gets low.

Click to expand...

That's a whole lot cheaper than anything else I've found that can work with gasoline. Although it doesn't mention the electronics being ignition protected, so I'm a little hesitant about putting it in an enclosed engine room. That, and it maxes out at 30 liters / hour for the sensor that can handle gasoline, so it's not big enough for my engines (WOT fuel burn is close to 30 gallons / hour per engine).

rslifkin said:

That's a whole lot cheaper than anything else I've found that can work with gasoline. Although it doesn't mention the electronics being ignition protected, so I'm a little hesitant about putting it in an enclosed engine room. That, and it maxes out at 30 liters / hour for the sensor that can handle gasoline, so it's not big enough for my engines (WOT fuel burn is close to 30 gallons / hour per engine).

Click to expand...

The company that makes Digiflow is based in Taiwan (no surprise). When I purchased, there was a U.S. supplier and a German supplier. The German supplier had a more complete online listing of what was available. I see now that there are many more U.S. suppliers, but I don't think that all Digiflow models are still represented online. I purchased through the German supplier because they showed what I needed online, but it was drop shipped directly from Taiwan.

My needs were for something that measured relatively tiny amounts of gas. Trolling with an outboard sometimes gets me down to where the gauge reads zero gallons per hour. But the gauge still accurately maintains the total amount used, which is my main concern when travelling in remote areas.

I bought a "kit" that had a meter model number designated by XXXXM, the M standing for "micro" and representing its ability to measure tiny usage rates. I don't know how much of the difference between large and small flow ratings is based on the impeller and how much on the gauge. Digiflow has a large selection. They may have a fuel-rated impeller for larger amounts.

Because mine was a kit, it had the wire from the impeller unit built in. No exposed electrical. The impeller unit itself uses an enclosed LED and a photo chip to read the spin rate. No exposed electrical and make-or-break sparks. Even if connecting a stand alone impeller unit like shown in the link, the electrical connection would be just like any other electrical connection in the bilge of a gasoline vessel. Meet ABYC standards and pray.

I've contacted Taiwan suppliers before and had responses faster (and in better English) that domestic distributors. Might give that a try explaining exactly what is required and asking for a model number for the kit.

As you can see from the link, the gauges don't look "nautical" at all. I assume that's why they cost 15% of a "boat" fuel monitor system. My particular model listed a limited range, but I found that the problem was the low end where it showed zero gph for a minute when trolling followed by .2 gph for a few seconds. Not too complex to work around. If I trolled for an hour I could just reference the total usage and figure an accurate gph for trolling or cruising at hull speed. I wouldn't be surprised if the high end readings, even above the unit's rating, are also more accurate than expected.

And for the price, put one on each engine, in which case 30 gph would have you covered.

I have had flowscans on the last two boats. For the Detroit boat its spot on. Once I learned that the readings were for only one engine. So I thought I was buringing 15 gph and was tickeled pink... but after a few long runs and filling the tanks I found out it was 30gph...

For the gas boat it was always off about 15-20%. I did not install it, and did not mess with it much as we always needed to refil after each trip due to the small tanks.

Wouldn't it be easier and cheaper to do it the old way?
Fill tanks
Burn some off for several hours at cruising rpm
Refill tanks
Maths.

While I did at one stage think floscan would be nice, I realised that once i got my cruise speed/burn dialled in it would not be used again.

Would rather the $1500 be spent in diesel.

Simi 60 said:

Wouldn't it be easier and cheaper to do it the old way?
Fill tanks
Burn some off for several hours at cruising rpm
Refill tanks
Maths.

While I did at one stage think floscan would be nice, I realised that once i got my cruise speed/burn dialled in it would not be used again.

Would rather the $1500 be spent in diesel.

Click to expand...

For a boat that pretty much only cruises at 1 speed, yes, that method works fairly well. But it doesn't cover more varied conditions well (multiple cruising speeds, finding best MPG speed going with or against wind / waves / current, etc.)