Fuel flow meter AD41?

[bubblehead]

Is there a diesel flow meter that can work with twin AD41’s? Or even just on one of them? Keen to be able to work out most efficient speed and usage?
I’ve done a fair bit of searching and seems i can only find them for petrol engines, ie no return line.
Surely there must be something available? Ideally I’d like to connect to the chart plotter to have the info available on screen?
Any advice would be great.

 

[Plum]

Is there a diesel flow meter that can work with twin AD41’s? Or even just on one of them? Keen to be able to work out most efficient speed and usage?
I’ve done a fair bit of searching and seems i can only find them for petrol engines, ie no return line.
Surely there must be something available? Ideally I’d like to connect to the chart plotter to have the info available on screen?
Any advice would be great.

They are certainly available, for example F127 Differential/Sum Flow Rate & Total Display with Fluid Temperature Correction, Optional Serial Communication, Analogue Output, Pulsed Output and Direction Signal | UK Flowtechnik Ltd

Or FUEL CONSUMPTION FLOW METERS (Double) Electronic | Engine Fuel Consumption Flow Meter Range

 

[PCUK]

Floscan is the best known and has been around for years.
Flotrex is cheaper and offers more functions. Both easy to install.

 

[bowler]

I had thought about these but decided that another guage for me to obsessively stare at whilst on the move was another one too many!

 

[kashurst]

Having had a boat with fuel consumption gauges I would not have them again. You spend all your time stressing about fuel burn instead of enjoying the day.
Better to spend the money making sure your boat and engines are in tip top condition and running equally well.

You can get a good idea how well your engines are running at cruise speed by measuring the temperature of the pipe from the turbo charger into the charge air cooler. If both engines are in good condition and running at the same rpm, the charge air pipe temp should be very similar. If it is 20 - 30 degs dfferent or more, the one wth the lower temp is not performing as well causing the better engine to work harder to maintain the same rpm. Harder work = higher compressed air temp.
It's very easy to measure with a cheap IR thermometer, wrap some black insulation tape around the pipe close to the input to the charge air cooler, same place on both engines. Once you are cruising and everything is at normal temperature, point you IR temp meter at the black tape and see how hot each pipe is and go from there. If much the same, happy days. If different someone on here will help figure out why.

If you post on here what make and model of boat you have someone will already have figured out best cruise speed in ideal conditions. There are also fuel consumption/prop demand curve charts for most engines on the internet so you can work out your best RPM when cruising. It won't be exactly right, but out at sea its never exactly right either.

 

[ChromeDome]

Floscan is the best known and has been around for years.
Flotrex is cheaper and offers more functions. Both easy to install.

Think Flowtrecs is the right name.

 

[PCUK]

Yes, it's one of those.
I should know as I've got one - doooh!

 

[ROSK]

A simpler approach may be to use Information from the engine consumption curves. I made an excel spreadsheet 8 years ago for my Windy 9800 with two AD41p-a engines. The curves give a good estimate for trip cost vs different rpm.
You only need to log the speed at different rpm. The curves requires a "perfect" propeller for the boat, but you could do a test run, refill, and adjust the formula with a percentage. Not sure how I can share an excel file.

 

[ChromeDome]

Curves can be a good indication.

However, the true burn of fuel relates to the hp produced (= required by the helmsman).

Brake Specific Fuel Consumption (BSFC) is measured by calculating the ratio between the fuel consumption and the power produced by the engine. The formula for BSFC is expressed as the fuel mass flow rate divided by the engine output power, resulting in the brake specific fuel consumption. This calculation is crucial for determining the efficiency of an internal combustion engine, reflecting how effectively it converts fuel into rotational power. Typically, BSFC is measured in units like grams per kilowatt-hour or grams per joule.

See examples here:
Brake-specific fuel consumption - Wikipedia

 

[ROSK]

We are maybe a bit off topic, but I would expect the fuel consumption [g/kWh] is covered, as both the fuel and hp can be related to rpm. I could not find the fuel consumption in [g/kWh] for aqad41, but found for aqad 40 in a technical bulletin (older different motor ).


For ships with multiple gensets it is important to know this curve as efficiency may drop 20-30% below 25% load. I can imagine picking an engine for a new boat it is also smart to address, but things get complicated very quickly.

For implementation to an existing small craft you need to find some kind of compromise. The necessary energy needed for the required cruising speed, the optimal propeller diameter with optimal area and number of blades (or strendrive), etc. So the inefficiency due to resistance of the hull, efficiency of the propeller in different speeds, the energy loss in the drive chain and BSFC - all matters.

I would consider:
* Optimal fuel efficiency (For the Windy between 2500 - 3000+)
* Best handling speed (For the Windy above 28 knots, 3200 rpm)
* Low rpm to reduce risk of engine failure for an 25 year old ish engine - rpm below 3300 for cruising speed. (I guess the engines can easily handle 3500 rpm also)
Looking at the estimated consumption curve you can see that the l/nm does not increase to much at higher rpm. If you only look at l/hour, it seems that it is much more expensive than it actually is.
My cruising speed was defined by this many years ago, 3200-3300 rpm for longer distances, and 2800 rpm if I was not really going anywhere particularly. Everyone may not agree, but I had the boat for 6 years without any problems with the engines.

To comment on the actual question from mr Bubblehead .You have the possibility of some fun DIY. You could buy 4 Shelly Uni Plus, and 4 cheap flow meters from ali express. A raspberry Pi with a Pican hat for getting gps and other data from the plotter. And then use Home assistant to make a dashboard presenting l/nm. (Just saying it could be done, I could not )

Connecting Raymarine NMEA2k data to Home Assistant

 

[vas]

@ROSK I got some cheap flow meters planning to do just that a few years back, only when I got them I realised what cheap flow meter really means in ali
I wouldn't trust that pos to deal with my freshwater toilet on board, let alone diesel

 

[oldgit]

My two penny worth is that the only critical need for an idea of fuel consumption is on any extended journey where you really need to know if you will have sufficient fuel in your tank to finish the trip safely, or a need to call in enroute to top up.
Need to factor in just how much usuable fuel is in tank(s) plus a calculation of what happens if a need to turn back or divert arises.
On a longish leg would normally set boat up on the speed / most economical speed /revs and leave the throttles until arrival.
A simple fuel curve can provide the information you need with smallish margin of error.

Never been interested in the fuel consumption per hour , purely just how long can you stay out there before you run out of fuel.
If the cost of a litre of fuel is going to be a big problem running a boat ......Best not buy one .


On recent(ish) trip, a boats fuel meter at 30 knots was displaying as guzzling over 200 LPH on a pair of D6s with those super efficient IPS.
VP claim it should be using about 160 LPH.
They cannot both be right ?


Volvo Penta Diesel | D6 370 & D6 435 | 370 / 435 hp | Fuel Consumption - Liters per hour

 

[ROSK]

My two penny worth is that the only critical need for an idea of fuel consumption is on any extended journey where you really need to know if you will have sufficient fuel in your tank to finish the trip safely, or a need to call in enroute to top up.
Need to factor in just how much usuable fuel is in tank(s) plus a calculation of what happens if a need to turn back or divert arises.
On a longish leg would normally set boat up on the speed / most economical speed /revs and leave the throttles until arrival.
A simple fuel curve can provide the information you need with smallish margin of error.

Never been interested in the fuel consumption per hour , purely just how long can you stay out there before you run out of fuel.
If the cost of a litre of fuel is going to be a big problem running a boat ......Best not buy one .


On recent(ish) trip, a boats fuel meter at 30 knots was displaying as guzzling over 200 LPH on a pair of D6s with those super efficient IPS.
VP claim it should be using about 160 LPH.
They cannot both be right ?


Volvo Penta Diesel | D6 370 & D6 435 | 370 / 435 hp | Fuel Consumption - Liters per hour

I agree they cannot both be right . There are probably a lot of people on this forum that know how the D6 works and performs, and this subject much better than me.
I would assume:
* the engine measurement is probably correct
* if Volvo claims it should do 30 knots with 160 l/hour, it would only apply when the boat is new, lightly loaded, clean hull. Maybe also with fuel at the right temperature.
* if Volvo claim it should use 160 liters at a specific rpm, it would be required that you can reach max rpm at wot. Propeller/ Marine growth may be a factor.

 

[wonkywinch]

I fly a small plane where the ballpark figure for fuel burn is 50 litres an hour (at over £2 a litre) so I produced this from the tables in the manual and worked out the optimum power settings for min fuel per nm.

 

[oldgit]

Knowing the average litres per hour is fine in a non tidal environment.
In the real world of tides 3/4 knots (or 25 Knot headwind) with or against you can amount to a considerable difference in the amount of fuel required to complete a journey.?

 

[wonkywinch]

Knowing the average litres per hour is fine in a non tidal environment.
In the real world of tides 3/4 knots (or 25 Knot headwind) with or against you can amount to a considerable difference in the amount of fuel required to complete a journey.?

Absolutely, flights are always planned to take advantage of the winds and it's better to fly slowly with a tailwind (maximise exposure) or faster into a headwind. The table is for still air and so it's easy to cross reference it to SOG in flight. Even planning software for light aircraft flights (Skydemon in the UK or Jeppesen Foreflight in the USA etc) can work out most efficient level to fly given forecast winds.

 

[bubblehead]

Thanks for all the replies, it’s been interesting to read. Especially ROSK, as I believe that may be similar size boat. Interesting figures.
It is for a Princess Riviera 286.
It’s certainly not for ‘how much is this going to cost’, I’ve been baiting long enough and accept that a day on the boat is exactly that, it gets topped up when it needs it. I’m having only just moved to this boat from a single petrol V8, I was just curious to see how they compared (but it seems the cost to find out is simply not worth it).
Thanks again.