Diesel flow measurement return line

[Pizzazz]

I am trying to install a fuel flow measurement sensor on a Cummins 6CTA8.3-m3 engine (450 hp). The engine manual says that the fuel pump puts in about 68 gph into the high pressure pump and the unused fuel is retuned via the return line to the tank.

I found this unit, Eurosens Delta PN 250 that is a differential flow measurement sensor that seems appropriately sized for this engine. In the installation manual the company suggests two options 1) install it on the supply and return lines in differential mod and 2) connect the return line to the second input of the Racor filter and measure only the supply line.

Their logic for suggesting option 2) is that it provides better accuracy which I can understand. However, at low speeds there will be massive amounts of fuel circulating through the racor filter per hour that will eventually get heated and could cause all sorts of problems. The fuel could vaporize, the high temperature will likely change the readings even more than the compromized accuracy, etc. The unit does have temperature compensation but still it does not look right to me. Other people say, it is no problem as long as you monitor the fuel temperature and do not exceed Cummins recommendation. Then you need to add a fuel cooler, which could be easy but will also increase the required suction pressure.

What is the proper way to do it?

Thanks,
SV Pizzazz

[GordMay]

My immediate, inexpert reaction, is that your reasoning [to avoid the recommended option 2] seems reasonably sound.

[mcarthur]

I had a quick look at the Eurosens a few years ago and talked with (what seemed to be) the manufacturer. But their overall price wasn't terribly far from a N2K Maretron install when the proven use/reliability and manufacturer backing is taken into account.

[RaymondR]

Quantify the increased accuracy and see if it is significant. If they are only talking about a percent or two it might not be worth the uncertainty #2 brings.

[Sailmonkey]

Seeing as the fuel is used to cool the fuel system, there’s no way I would hook the return back to the racor.

Besides that, do you really want to keep a constant eye on fuel temperature? Then what do you do if your transiting the ICW through narrow no wake zones and your fuel temperature is too high?

[tkeithlu]

Amen, Sailmonkey. Returned fuel needs to go the biggest available heat sink - the tank.

[flightlead404]

I've done several differential installs over the years and always been within a couple 1/10ths of a gallon over 100's of gallons.

[RaymondR]

Originally Posted by flightlead404

I've done several differential installs over the years and always been within a couple 1/10ths of a gallon over 100's of gallons.

That would settle it for me.

I'd do installation #1 and keep a check of indicated flow x time versus tank dip over a constant throttle setting, extended run to get an idea of the accuracy.

[MV Caroline]

I agree with Mcarthur, Maretron is what I'm using n2k compatible with many other monitoring options as well. Really nice systems, pricey but they work dependably.

[Simi 60]

I have considered these for $40

One on in, one on out, simple maths gives fuel burn

For us, sight tubes and a measured 1000 litres at cruising rpm gave us the required data.




https://www.ebay.com.au/itm/17468768....c101196.m2219

[skipperpete]

Originally Posted by Pizzazz

I am trying to install a fuel flow measurement sensor on a Cummins 6CTA8.3-m3 engine (450 hp). The engine manual says that the fuel pump puts in about 68 gph into the high pressure pump and the unused fuel is retuned via the return line to the tank.



I found this unit, Eurosens Delta PN 250 that is a differential flow measurement sensor that seems appropriately sized for this engine. In the installation manual the company suggests two options 1) install it on the supply and return lines in differential mod and 2) connect the return line to the second input of the Racor filter and measure only the supply line.



Their logic for suggesting option 2) is that it provides better accuracy which I can understand. However, at low speeds there will be massive amounts of fuel circulating through the racor filter per hour that will eventually get heated and could cause all sorts of problems. The fuel could vaporize, the high temperature will likely change the readings even more than the compromized accuracy, etc. The unit does have temperature compensation but still it does not look right to me. Other people say, it is no problem as long as you monitor the fuel temperature and do not exceed Cummins recommendation. Then you need to add a fuel cooler, which could be easy but will also increase the required suction pressure.



What is the proper way to do it?



Thanks,

SV Pizzazz

Since you’re in the US, why not shop local and buy “Floscan”, they make em for every fluid flow application and have been the leader for many years.
Oh, don’t connect the return to the Racors, often there is aerated fuel in the return line which could/would raise problems other than heat rejection.
Pete.

[Simi 60]

Originally Posted by skipperpete

Since you’re in the US, why not shop local and buy “Floscan”, they make em for every fluid flow application and have been the leader for many years.

I wonder why the need?
How often do you need to know fuel burn?

I would have thought once you had a timed run on measured fuel at cruise rpm you are done and would never look at the device again.

[Bill O]

Originally Posted by Simi 60

I have considered these for $40

One on in, one on out, simple maths gives fuel burn

For us, sight tubes and a measured 1000 litres at cruising rpm gave us the required data.

+1 for the old school simple sight glass technique to measure general fuel consumption.

The problem I see with measuring the fuel flow in/out (differential), the output flow would need to be adjusted for the increased fuel temp to be accurate. Doubt the cheap electric flow meters would have this capability.