Figuring out Fuel flow for a 42hp motor

[lamadriver]

Good Morning.

I want ot buy a fuel flow measuring kit form Maretorn. it has two sensors to measure the flow to and the return form the motor.

I have 42hp Vetus 4.17 which is a misubishi S4L2. I burn just under 3 liters an hour.

These sendors have a range in what they measure volume per hour.

how do I figure out what gets pumped though in an hour. Does 20 gallons an hour sound about right?


LD

[a64pilot]

Sounds a little high, but most transducers have a range like 10 to 50 GPH or so, not just one number, what ranges are there?

[lamadriver]

Part Number: M1AR
Flow range : 2 to 100 LPH (0.53 to 26.4 GPH)

Part Number: M2AR
Flow range : 25 to 500 LPH (6.60 to 132 GPH)

Part Number: M4AR
Flow range : 180 to 1500 LPH (47.6 to 396 GPH)

and bigger........

I thought i had seen here some where there is a formula for what the use rate is per hour to figure out what the flow rate would be

LD

[model 10]

There is a rule of thumb. 1/2lb per hr per HP. If you were running at full power you would be using 21lbs per hr or 3gal per hour.

[a64pilot]

I think he needs to know how much total fuel is pumped including what goes back to the tank, so he can correctly size his transducers.
He knows roughly his fuel burn is just under 3L an hour.

I guess one way is to remove the return fuel line and at cruise power settings see how long it takes to fill say a fuel jug, then add that to fuel burn and you know total fuel pumped?

[a64pilot]

My best guess is the M2R, but think you need to verify cause I could see how maybe the M1R may be it too. Some engine do return a surprising amount of fuel, some it's mostly just a dribble
Can you contact the manufacturer, I bet they know.

[model 10]

Originally Posted by a64pilot

I think he needs to know how much total fuel is pumped including what goes back to the tank,

If the most he could use is 3gph and he is using 3lph then the return line tx needs to be able to handle the difference.

[Adelie]

M1AR is the only one that will work for the OP. All the others won't even start registering the flow at full throttle.

Rule of thumb is 18hp/gal/hr. for diesels. That's 2.33gal/hr or 8l/hr WOT for a 42hp motor.

Even if you are returning as much as you burn that's only 16l/hr in the forward which doesn't even move the needle the M2AR. In reality the listed minimum range is probably just for the burn amount so the meter is even less appropriate.

Even with the M1AR I would expect the meter to stop reading somewhere about 1/2 throttle or maybe start losing accuracy.

[Pole]

Originally Posted by lamadriver

Good Morning.

I want ot buy a fuel flow measuring kit form Maretorn. it has two sensors to measure the flow to and the return form the motor.

I have 42hp Vetus 4.17 which is a misubishi S4L2. I burn just under 3 liters an hour.

These sendors have a range in what they measure volume per hour.

how do I figure out what gets pumped though in an hour. Does 20 gallons an hour sound about right?


LD

I have the same engine in my boat - A Dix 38 weighing 11 tons. I have done about 200 hours and done the fuel calculation by comparing fuel use to engine hours.

Bear in mind its not an exact science because RPM's are not constant - sometimes idling, sometimes at 2 000 RPM in the cruise, and sometimes just going along slowly. My burn is a constant 2.75 Liters per hour. Thats about 3/4 USG/hr and just over 1/2 ImpG/hr.

The OP states he burns just under 3 liters per hour. Just like me!

If you know that why install a flow meter?

And if you do want to install a flow meter, I would say the range it should measure between 0.5 to about 6 liters per hour.

[a64pilot]

Some engines like Cummings return 80% or so of the fuel that is pumped and only burn 20% , so fuel that has to be measured is what four times what the burn rate is?
Some engines with rotary injection pumps only return 20%

I think a call to the engine manufacturer or a good service shop is in order.
Amount of fuel pumped and filtered is often way out of line with what is burned, these types of fuel injection systems are in effect fuel polishers

If not call, it's too easy to measure return rate.

But surely the small transducer is the one

[lamadriver]

Originally Posted by Pole

The OP states he burns just under 3 liters per hour. Just like me!

If you know that why install a flow meter?

.

Are you the dix 38 just down from Jerrican ( dix43p) at FBYC?

Ill be passing through sometime in September. We can have a Dix convention

I find that the burn rate varies greatly between 1200-2000 rpm. I almost never run over 200 rpm and find the sweet spot is some where around 1600 for fuel economy vs speed.

I have a 5500 miles passage coming up with expected 1/4-1/3 of it motoring accross the top of the south Atlantic high. Being able to tweak the fuel consumption and drop it from 3 ish to just over 2 is huge.

A64: Im pretty sure it is about 80 % return.

[Pole]

Hi Lama, yes thats me. Boat name is La Mar and my name is Paul (in afrikaans they call me Pole hence my user name). I work overseas but I'll be around Aug/Sep. Please look me up and we can compare notes...

[a64pilot]

Originally Posted by lamadriver

A64: Im pretty sure it is about 80 % return.

Still puts him with the small transducer I think.

One day a I will measure my Yanmar cause now I'm curious.
Was clogging 2 micron fuel filters on my generator often and didn't understand why, then found out that it returns four or five times the fuel it burns, and then it made sense, so I went with a Racor 500 and now, no problem.
Better cause it's a real common size too.

[Adelie]

I did a little research on return volumes.

Appears that return vary from almost nothing so something approaching 97% (30:1).

M1AR still looks like the right meter.

http://www.ybw.com/forums/archive/in.../t-325453.html

[a64pilot]

Originally Posted by Adelie

I did a little research on return volumes.

Appears that return vary from almost nothing so something approaching 97% (30:1).

M1AR still looks like the right meter.

http://www.ybw.com/forums/archive/in.../t-325453.html

Yes, the high return ones are in effect fuel polishers. They circulate the entire fuel tank contents through both filters several times before it's burned.
My Duramax Diesel truck even had a fuel cooler mounted to the tank that cooled the fuel prior to putting it back in the tank, it was common rail and the drivers that fired the fuel injectors were high amperage and fuel cooled, so return fuel was a cooling medium on that common rail motor.
I'd be surprised if it isn't on some Marine common rails too.

On edit a Duramax and I assume most any common rail uses more electricity to run than any gasoline engine, making those injectors open and close against 30,000 PSI fuel pressure in milliseconds take POWER. I bet that thing likely used 20 or 30 amps to run those injectors, maybe more?