Fuel flow measurement on small diesel engines

[nigelmercier]

I wonder how much one of these would restrict the flow, especially with the nozzle in place.

 

[rogerthebodger]

I wonder how much one of these would restrict the flow, especially with the nozzle in place.

Thats a very good point and the same issue with the size of the venturi needed.

The ultrasonic transducer posted early would be the solution but the cost at the moment is too high for my used anyway unless any one knows how to build a DIY one from ready available components. From what I have read the timing down to picoseconds are needed.

These are used on F1 cars where cost is not an issue

 

[jfm]

If you want to do this with accuracy the best kit on the market is a Maretron ffm100 with a flow meter in the flow and return lines. They make flow meters suitable for low flow rates/small engines. The output from ffm 100 is fed via N2K to any device that can read N2k and display fuel data eg a Maretron dsm 250, garmin gmi20 or gmi10, and most modern MFDs
I use maretron ffm100s on my gensets and they're very good. Far better than flowscan gear.

 

[Lon nan Gruagach]

Thks guys the small Conrad flow transducer is a possibility but the lower limit and published accuracy is still a problem.

If you consider the 0.01 lit/min is 0.6 lit/hr and at 1lit/hr per 5 hp rule of thumb that is 3 hp. and if you consider the published accuracy of +- 2% which is normally at max flow that would be +- 0.02 lit/min so that does not show good accuracy of low flow rates and as there is no accuracy v flow rate chart how accurate would the reading be.

This is the one posted with the 1mm nozzle max flow 1 lit/min 60 lit/hr which is 300 hp. So my 63 max hp say cruising at 40hp this is less than 15% of the flow meter capacity where the accuracy would be questionable IMHO

Any one disagree with my assumptions please correct me.

One wee niggle.. taking the accuracy specification, you are correct, however there is "Repeatability of frequency response = +/- 0.5%". You would be able to calibrate it to obtain 4 times better accuracy.

 

[Yngmar]

Found a review of the Maretron FFM100: http://www.panbo.com/archives/2014/..._monitor_test_part_1_as_good_as_it_gets_.html

Although numbers may be somewhat skewed by this being a massive stinkpot engine, it's very interesting how much fuel is being returned versus used, especially whilst the engine is idling. That tells me even the very accurate positive displacement meters used here are barely adequate, as the difference between supply and return is so small compared to the total flow (less so under load, but still only about 25% of the fuel flow is being used).