can you buy a diesel flow meter?

Rivers & creeks

Rivers & creeks

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The installation on the Kipper has an odd shaped and tapering fuel tank, it means estimating fuel usage is a dark art.

On the positive side the system is a single outlet going to a banjo fitting with the engine return so the flow from the tank is the actual fuel consumed. Can I fit an in-line flow meter? Fancy electronics to the instrument panel isn't necessary, just a continuous counter in situ is all that's needed. We sail on at least 50% of our passages and when we sail, we sail well, but when the old girl has to motor we just have to motor and some of our trips this year were long. I got the impression on some of those trips, watching the sight guage that there might be a real sweet spot in terms of rev/miles/litres used and I'd like to find it. Any cost effective ideas?

Thanks.
 
Not sure there's a "cost effective" solution. Fuel flow on a small diesel is low, so a good quality sensor is needed if you want it to be accurate. If you have a separate fuel return to the tank, you need 2 sensors and an instrument which will subtract one from the other to give net usage.

Floscan are supposed to be good, but you'd be looking at around £1000.

If you have Garmin equipment, there's a Garmin fuel sensor at around £150, I think, but you'd need to check compatibility with the plotter.
 
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pvb said:
Not sure there's a "cost effective" solution. Fuel flow on a small diesel is low ...
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For general info for those who have feed and return ...
nigelmercier said:
Following on from this thread where I was asking if a Racor 120AT Diesel Fuel Filter would have enough throughput at 57 litres per hour: http://www.ybw.com/forums/showthread.php?374311

I have just disconnected the return pipe on my Volvo Penta MD22P-B and timed the return flow at 1000 RPM: in 5 minutes I got 1.5 litres. So that's 18 litres / hour, plus perhaps 2 litres per hour that is being used, total about 20 litres per hour.

The return rate didn't seem to noticeably increase at 2000 RPM, I wonder if I need to check this.
Click to expand...
 
When I first fitted out my current boat I fitted a Navman diesel 3200 fuel flow computer but found it would not register the flow taken by my 63 hp 4 cylinder engine so I had in my junk box a turbine flow sensor from RS
http://uk.rs-online.com/web/p/flow-controllers/5082704/?origin=PSF_421247|cav

I fitted it with a frequency meter I also has but this also would not register fuel flow but would register when I blew through and it would register the flow from my fuel transfer pump. I concluded that I was not sensitive enough.

This looks interesting with info on different types and will study it later

http://uk.rs-online.com/web/generalDisplay.html?id=automation&file=flow_manage_02

This company also looks interesting but the min flows look similar to the RS one I already have.

If I could find one that would display on my frequency counter I could then use a micro controller of PIC to do all the calcs and scaling.

Fuel computers that measure flow seem only available for high power engines as used in Mobos. The small engine flows computers as in my 4x4 seem to get the info/display from the electronic fuel injection system unless some one knows otherwise.

Also considering doing some tests with a small orifice flow meter and a differential pressure transducer

Info here

http://www.instrumentationtoolbox.c...tation+and+control+engineering)#axzz3D2B007PZ

differential pressure transducer here

http://www.ebay.com/itm/140999596718?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
 
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Of course there are alternative methods.
The best option for measuring the flow rate is with a Mass Air Flow Sensor, as used for MPG figures in most cars.
Next, you could do a calculation using the RPM using the published data for your engine.
On my boat I've built a fuel gauge that can be calibrated to the shape of the tank, but this isn't strictly necessary, you could just fill up 10 litres at a time and note the reading.
 
I went down that road in the past - to no avail. Too little flow for any economic reader. Had the Lowrance reader in my huge outboard once - and it worked a treat at those ridiculous gas-guzzling rates.

So, I just installed a vertical pipe off the valve used for cleaning the tank (most tanks have that valve in place), so now I open the valve at the bottom and see the very exact fuel left (Communicating vessels). I know this is not the ultimate answer, but it is cheap and exact.

Plus, all the crud of the tank ends at the bottom of the hose loop, so I can slowly see how much of it there is in the tank (not much, so far).

PS> I marked the fuel tank with 10 litre notches, so...
 
If you want it to do more than counting (like calculations), you need an instrument to compute results.

A bit confusing that flow to and from the engine runs in the same line as that would cause the problem normally solved by separating the flows: Bubles!

I have only once seen a setup (Nauticat 44) where a Tigerloop allowed the air to escape, hence using one line only from the tank. It worked although Tigerloop is intended for heating/domestic use and installation in a closed compartment will take an extra hose to route the fumes out (or into the tank fill hose).
 
No problems on ours caused by one pipe, it's run that way since 1974 and was the usual installation method back in the day. In last month's PBO the ask the expert reply commented that this type of installation stops warm fuel returning to the tank and gently heating it and encouraging bug growth.

Seems the only way with our shaped tank is to get it almost empty and slowly fill at the marina marking it off at 20l intervals.
 
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