diesel fuel flow sensor

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pjsmith

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Hi,

I'm looking for an _economical_ fuel flow sensor. At best it only needs to output pulses. I'm going to interface it with somthing else. Flow rate about 1-2 liters an hour. Lowrance do somthing that looks perfect but it seems to be gas only.

Anyone come across anything I might be able to use?

Thanks.
 
First off all . This doesn't work with most diesels. They have a flow that goes back from the injectors to the dieseltank.
So you would need two and subtract the results.
This would be very inaccurate!
Second , those low flows are very hard to measure. Flowmeters for fuel flow do exist but they are used on fast boats with big engines.
So I guess you will have to buy a tank level indicator and calibrate it by pooring in diesel ai intervals of say 1/2 liter.
You then can use the gauge for calculating the fuel consumption.
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Could you utilise something from a diesel car? My peugeot displays real-time mpg figures so it must be measuring flow to fuel pump minus return to fuel filter (that's where the return goes on mine I think, from memory). These bits from a scrapyard shouldn't cost much should they? Can't be in that much demand (yet).
 
pjsmith said:
Hi,

I'm looking for an _economical_ fuel flow sensor. At best it only needs to output pulses. I'm going to interface it with somthing else. Flow rate about 1-2 liters an hour. Lowrance do somthing that looks perfect but it seems to be gas only.

Anyone come across anything I might be able to use?

Thanks.
Click to expand...

Floscan do a system that uses sensors on both the flow and the return. It is designed to calculate the nett useage and I have heard it works well. Problem is tha it is expensive.

I also wanted one, but gave up the search as I couldn't find anything for less than £3000 installed. And I wanted the data output to NMEA 2000 as well, which would cost even more.

If you find anything please pm me.
 
If I can find an affordable sensor for flow and return I could knock up a NMEA version very cheaply less cost of sensors. These will be added to my arduino boat computer to record fuel usage. That bike one is the sort of thing I'm after. I'll see if I can find any others. I guess the lph usage is going to be similar.
 
Plenty of suitable ones on that conrad site. Fuel consumption of my engine is probably only 1 litre or so per hour, but does anyone know very approximately how many litres will be cirulating through the flow and return? I've no idea how much gets returned to the tank. Trying to work out which flow meter to get.

Thanks.
 
In most cars with diesel engines the consumption is not measured by meams of a flowmeter but by using the setting of the governer or nowadays the setting of the injectors at a the common rail system.
So that cannot be used in a boat because you simply don't have those normally.
As for the link to Conra:
http://www.conrad.de/ce/de/product/...oductname=DURCHFLUSS-IMPULSGEBER-INDUKTIV-POM
The smallest flowmeter starts at 0.025ltrs/minute which is 1.5 ltrs/hr. Its clear that you cannot use it in a boat consuming only 1-2 ltrs/hr.
Below minimum flow they get very inaccurate or don't measure at all.
As said already , in a powerboat they are fine!
Its a pity but a fact!
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You are right , I overlooked it!
But how are you going to deal with the flow back to the tank?
If you install one , put the results in a thread . Would be very interested!
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I'll update the thread once I've tested them. I think the flow rate will be far higher than consumption due to the return flow back to the tank. We'll just measure both sides and subtract the difference. The accuracy on these is quoted at 2% over the range. That's certainly good enough for me and it might even get better once calibrated.
 
Last edited:
ok, it's an old thread, I know!

anyone managed to test these sensors and made any sense out of them?
Very much interested.

cheers

V.
 
vas said:
ok, it's an old thread, I know!

anyone managed to test these sensors and made any sense out of them?
Very much interested.

cheers

V.
Click to expand...


I've been thinking about this and think it might be possible with a sensor that only measures flow and not return.
If you fit a flow meter on the output of the tank then fit a small day tank ( like the old HDML's had I think) AFTER the flow meter. The day tank feeds the engine & takes the return from the injectors. The flow meter would then only measure fuel from the main tank.

You may need to tweak or have a day tank of same height as main tank. My head hurts trying to figure that bit out :)

I know this is an old thread but it always comes up on a Google search :)

Cheers

Don
 
Diesel flow rates?

Like many owners I'd like to know more about how much fuel I'm using and how it varies with different sea conditions, points of sail, motor sailing etc.

I've been looking for one for years and the subject keep cropping up on this forum.

The way I understand it goes something like this:

A traditional diesel engine (i.e. not a modern car diesel, which seems to be computer controlled) has a mechanical governor, which is designed to keep the engine running at a constant RPM, if the load goes up, it pumps more diesel in to keep the revs constant, if the load goes down, it uses less fuel.

On a boat the load ( to a first approximation) at any given rpm is dictated by the advance coefficient i.e. the ratio of the pitch of the prop' to the speed the boat is traveling through the water. the pitch of the prop. The pitch is generally fixed (not for Autoprops which are different). So as the boat slows down the load goes up and the diesel uses more fuel and vice versa.

To cope with this varying requirement for fuel the lift pimp is sized so that it can provide enough fuel when the diesel is running at maximum load at any RPM.

In my case with a 54hp Yanmar 4JH4E, the maximum fuel consumption at 3000 RPM is quoted as 12 L/hr at 3,000 RPM. Working from the data in the workshop manual, the mechanical lift pump can deliver 27.6 L/hr at 3000 RPM, so 15.6 L/hr is being returned to the tank.

That means I'm looking for two fuel sensors, one to measure a maximum of 27.6 L/hr and the other to measure a maximum 15.6 L/hr.

To look at the other extreme case, if I'm motor sailing and the wind picks up so that the boat is going faster than the motor would drive it, i.e the advance coefficient is 1 or more ( in effect the prop' is acting like a generator) then the diesel will be using very little fuel. So the difference between the flow and return to tank will be very small. In this case any small differences between the calibration of the two sensors will be dominant and the readings will be very inaccurate.

From this starting point I could then workout how accurate the sensors have to be to allow me to measure a fuel consumption of, say 0.25 L/hr with an accuracy of say 5%.

Am I on the right track here?

I won't ask for comments, I'm sure I'll get them anyway!
 
concentrik said:
Could you utilise something from a diesel car? My peugeot displays real-time mpg figures so it must be measuring flow to fuel pump minus return to fuel filter (that's where the return goes on mine I think, from memory). These bits from a scrapyard shouldn't cost much should they? Can't be in that much demand (yet).
Click to expand...

I'd guess your car is common rail, so no return to tank.
 
A couple of different approaches that may be worth considering - 1) mount the fuel tank on load cells - you could then take a continuous reading of the tank weight, average it out to compensate for movement, and get a pretty good idea of the weight of fuel used.
2) Use one or more ultrasonic sensors inside the fuel tank to measure the fuel level or the free space volume, again averaging out the values to give a measure of fuel volume used.
 
Ian_Edwards said:
Like many owners I'd like to know more about how much fuel I'm using and how it varies with different sea conditions, points of sail, motor sailing etc.

.....

A traditional diesel engine (i.e. not a modern car diesel, which seems to be computer controlled) has a mechanical governor, which is designed to keep the engine running at a constant RPM, if the load goes up, it pumps more diesel in to keep the revs constant, if the load goes down, it uses less fuel.

....
Click to expand...

How is the pump delivery rate controlled?

If it's done by increasing the speed of the pump then it might be possible to add a sensor to the pump and use that as an approximate measure of the fuel use. IE treat it as a metering pump.

Just a thought....
 
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