Cummins 450c Fuel Flow

[vas]

I did the maths on this on here a few years ago, but happy to do the sums again. This might take a while, so bear with me.

Trevor,

you did the maths for me sometime ago, don't bother doing it again!
Here it is:

http://www.ybw.com/forums/showthrea...-for-various-HP-engines&p=5625515#post5625515

whole thread is on same topic (with a slight twist), worth a read.

cheers

V.

 

[MapisM]

http://www.ybw.com/forums/showthrea...-for-various-HP-engines&p=5625515#post5625515

whole thread is on same topic (with a slight twist), worth a read.

Agreed, interesting reading indeed.
Thanks V for finding it - also because I missed, it back then.

Ref. SH6K maths, he definitely has a point, and in principle I can't fault his reasoning.
Otoh, I would think that his conclusion (1% inherent error in flow sensors potentially implying a 20% error in actual fuel burn numbers) is not only a worst case, but a very unlikely one, for several reasons:
- in a 'normal" pleasure boat usage, the temperature/viscosity excursion is not much - particularly inside an e/r, once reached the operating temperature;
- afaik, in most engines the return is well below 90% of the feed flow;
- the 20% error could only be reached assuming that both feed and return sensors are constantly giving an "opposite" 1% error (always more in one sensor and less in the other), and that is unlikely to say the least, considering that the flow is variable in both.

All that said, I couldn't agree more with his final statement: Vas, if you managed to build a decent sensor at a much lower cost vs. what can be found on the market, I'm also all ears! :encouragement:

 

[MapisM]

What I have discovered recently on my Lorenz plotter is a time to destination functionality .
So along with the L/ Hr on the MAN screens , I can see how much the trip will use .
A bit of real mental maths work out the € cost.

Naah, I don't think that's the whole point of having real time fuel burn numbers, in a boat.

Leaving aside the transition speed range, which as you say is irrelevant because nobody in his right mind would cruise in that sort of SD attitude in a P boat, It doesn't take a computer to know that the fuel burn is very low at D speed and much higher at P speed, with just little differences between low and high P speeds.

It's when you are somewhat restricted in your speed choice by the sea conditions, that it's interesting to see in real time not just the L/Hr, but also the L/Nm, because that can be relevant to the decision of if and how to adapt your speed, and possibly also the route.
And the only way I'm aware of for doing that is by trial and error - i.e. change speed, see what happens, repeat.
Then change course, see what happens, repeat. Then both.
Very unpractical to do, if you should throw also any mental math into the equation...

 

[MapisM]

What I have discovered recently on my Lorenz plotter is a time to destination functionality .
So along with the L/ Hr on the MAN screens , I can see how much the trip will use .
A bit of real mental maths work out the € cost.

Naah, I don't think that's the whole point of having real time fuel burn numbers, in a boat.

Leaving aside the transition speed range, which as you say is irrelevant because nobody in his right mind would cruise in that sort of SD attitude in a P boat, It doesn't take a computer to know that the fuel burn is very low at D speed and much higher at P speed, with just little differences between low and high P speeds.

It's when you are somewhat restricted in your speed choice by the sea conditions, that it's interesting to see in real time not just the L/Hr, but also the L/Nm, because that can be relevant to the decision of if and how to adapt your speed, and possibly also the route.
And afaik, the only way to do that is by trial and error - i.e. change speed, see what happens, repeat.
Then change course, see what happens, repeat. Then both.
Very unpractical to do, if you should throw also any mental math into the equation...

 

[MapisM]

I suspect L/nm will come from using GPS which will give L/nm over the ground which will vary considerably given tidal flow. I'd prefer to use the log output so I'd have L/nm through the water. But apart from this, just L/hr on its own would be fine. I wouldn't want to change the Fleming instrument panel, so separate insts would be OK.

Actually, when considering fuel burn and possibly residual range, wouldn't SOG be more relevant than STW also (and in a sense even more so) in tidal waters?
Regardless, as long as you have an instrument capable of sending STW as a NMEA output, and you feed the Floscan with that, I see no reason why it shouldn't do the same calculation that it can do with SOG...

 

[Portofino]

Naah, I don't think that's the whole point of having real time fuel burn numbers, in a boat.

Leaving aside the transition speed range, which as you say is irrelevant because nobody in his right mind would cruise in that sort of SD attitude in a P boat, It doesn't take a computer to know that the fuel burn is very low at D speed and much higher at P speed, with just little differences between low and high P speeds.

..

Agree , but it’s surprising how efficient if that’s the correct word ( suspect it ain’t,t ) running at fast P is .
Take100 mike trip Cannes to Corsica .
At my D 825 is 9 something knots in a normal sea so 10 miles / hr = 10 hr burns 40 L / hr so 400 L
So to do that. That’s a long day with “ watch planning “ etc for the helm , cooking maybe bouncing along if choppy , for ever looking a passage planner , wind n wave data wondering if it’s accurate
Arriving to find “ no room at the inn “ — Ok anchor off ,- but you risk a crew mutiny

Alternatively. At 27 knots journey takes 3 hrs. Fuel used 3 x 180 L / hr = 540 L , only 140 L more .
3 hrs means we can get up any time and obviously arrive for Lunch if we want ,never mind joining a Med high season Bun fight between 4-6 pm at a marina
Crew happy. No risk to marriage etc

But I could use 1 st click 600 rpm burns 24 L , 7 knots so extends the trip by 4 hrs to 14 , so now it’s turning from a liesure activity to some sort of expedition ? set off before dark. Arrive after dark , snag a pot , not one but two ,one 10 mins out from the start. Another 5 miles away from Corsica! —both in the dark .
And think about the ride. Beam sea rolls etc. .

I think you have to use the thing ( p boat ) as it was designed to be used .

Then think about longevity of the engines , even with Italian tune ups in some unscientific formula , it’s gotta be better if EGT,s are 550+ , not lower .eg @ 600 rpm they drop to a goo / sludge forming / ring leaking 125 degrees ugh !!
Your killing them slowly.

Oil temp @ P is arround 100 degrees. It drops to 70 @ D .
I understand Piers Cummings man has told him 1150 rpm @ 8 ‘knots is ok because the oil temp is maintained ??
Buts that’s built for D / SD — ours arn,t. Well mines not

 

[MapisM]

No day tank, just four separate tanks....

Piers, there's another thing which popped to my mind, while re-thinking of Fleming fuel tanks arrangement.
As I recall, they are built in fiberglass. If so, can you possibly confirm at which pressure they were tested?
There should be a plate somewhere on one of them stating the total capacity, the year of construction, and the pressure at which they were tested before installation.
I'm asking because that's something which we debated in another thread, and I'd be curious to hear about Fleming construction, in this respect. :encouragement:

 

[vas]

Actually, when considering fuel burn and possibly residual range, wouldn't SOG be more relevant than STW also (and in a sense even more so) in tidal waters?
Regardless, as long as you have an instrument capable of sending STW as a NMEA output, and you feed the Floscan with that, I see no reason why it shouldn't do the same calculation that it can do with SOG...

P.,

afaik plotters short that for you, so you got various types of output to play with, not a problem, getting accurate realtime consumption values to them IS the problem

fwiw, I did a bit more searching, came across some new stuff and checked again this:
https://www.massflow-online.com/sho...3.html?zenid=cfg6mvk4ii8572hvnu4o6cjk6ikm8upq

looks too good to be true at 350euro per engine (up to 350HP) and 460euro per engine 400HP+ . It is dual sensor (means it has flow in and back measurement) and not too expensive (compared to 900 for floscan NMEA2000 + cost of sensors..., or 1400 for Maretron)

Will investigate further, ask some Qs and come back.

cheers

V.

 

[burgundyben]

Surely the solution here is to re-power the boat with QSC's?

 

[Piers]

Piers, there's another thing which popped to my mind, while re-thinking of Fleming fuel tanks arrangement.
As I recall, they are built in fiberglass. If so, can you possibly confirm at which pressure they were tested?
There should be a plate somewhere on one of them stating the total capacity, the year of construction, and the pressure at which they were tested before installation.
I'm asking because that's something which we debated in another thread, and I'd be curious to hear about Fleming construction, in this respect. :encouragement:

There's nothing like that on these tanks. I've asked ask Fleming, but I'm doubtful - they seem to have 'lost' all the construction information about Play d'eau.

 

[Piers]

Actually, when considering fuel burn and possibly residual range, wouldn't SOG be more relevant than STW also (and in a sense even more so) in tidal waters?
Regardless, as long as you have an instrument capable of sending STW as a NMEA output, and you feed the Floscan with that, I see no reason why it shouldn't do the same calculation that it can do with SOG...

So if Play d'eau was in a head tide of 7 kts and making 7kts through the water, wouldn't Floscan show the most enormous consumption/nm if using SOG rather than STW?

 

[Piers]

Surely the solution here is to re-power the boat with QSC's?

Aren't these electronically controlled? If so, I can't bear the thought of (in effect) asking Bill Gates for more power and hearing I first need an update. I have a serious mis-trust of electronic engine controls. At least when I move the throttles or gear levers on Play d'eau I know I'm moving controls mechanically (or hydraulically).

 

[burgundyben]

Aren't these electronically controlled? If so, I can't bear the thought of (in effect) asking Bill Gates for more power and hearing I first need an update. I have a serious mis-trust of electronic engine controls. At least when I move the throttles or gear levers on Play d'eau I know I'm moving controls mechanically (or hydraulically).

Yes. They are. That exactly the point! Get over the luddite approach and look objectively at the benefits. Its a no brainer.

 

[MapisM]

There's nothing like that on these tanks. I've asked ask Fleming, but I'm doubtful - they seem to have 'lost' all the construction information about Play d'eau.

Aha, no worries, thanks anyway.
But is she pre-CE? My understanding is that this sort of tank "labelling" is one of the formal RCD requirements.
Regardless, it's a pity that - as I understood from the other thread - the support is going downhill since TF left.
Btw, just out of idle curiosity, do you know who the new shareholders are?

 

[MapisM]

Aren't these electronically controlled? If so, I can't bear the thought of (in effect) asking Bill Gates for more power and hearing I first need an update. I have a serious mis-trust of electronic engine controls. At least when I move the throttles or gear levers on Play d'eau I know I'm moving controls mechanically (or hydraulically).

Amen! :encouragement:

 

[MapisM]

So if Play d'eau was in a head tide of 7 kts and making 7kts through the water, wouldn't Floscan show the most enormous consumption/nm if using SOG rather than STW?

Well, yes, but that reflects exactly the reality.
In those conditions you'll never reach your destination no matter how close it is, and how full your tanks are...

 

[Piers]

Aha, no worries, thanks anyway.
But is she pre-CE? My understanding is that this sort of tank "labelling" is one of the formal RCD requirements.
Regardless, it's a pity that - as I understood from the other thread - the support is going downhill since TF left.
Btw, just out of idle curiosity, do you know who the new shareholders are?

Thanks for the info re CE and RCD. I will press the point. re shareholders, no I don't know as fact, but what I've been told by a Dealer is that the company was sold to the General Manager (Duncan Cowie) and Tony's nephew who lives in Taiwan.

 

[Piers]

Yes. They are. That exactly the point! Get over the luddite approach and look objectively at the benefits. Its a no brainer.

Luddite I may be, but I've been involved in too many tows when throttles have failed, and more than one incident when I was almost rammed when moored up by throttles / gears that would not disengage. Whether user error or not, it seems to me to introduce a level of potential error, especially when suddenly under pressure.

 

[jfm]

I wouldn't touch floscan. They measure fluid flow using something like paddle wheels, and they are a pita to calibrate - read the instructions online and figure out how the hell you will calibrate them.
The ones to buy are maretron. Beautiful things. Individually factory calibrated, flow measurement by gear pump working in reverse as a turbine, and inbuilt temp sensors with an algorithm that automatically corrects for temperature. Output is n2k so no need to run cables to dashboard if you already have n2k in e/room

I fitted these (4off) to both my gensets and they work beautifully. Highly recommended and streets ahead of floscan.

When running the boat I always have lpm and range showing on the dash (from the cat ecus). Much more useful than lph so far as nav is concerned, imho.

 

[MapisM]

When running the boat I always have lpm and range showing on the dash (from the cat ecus).
Much more useful than lph so far as nav is concerned, imho.

I agree, but waddumean by "from the Cat ECUs", J?
Afaik, they are totally unaware of the actual boat speed, and also of tank capacity.
Am I right in guessing that you just "read" the instantaneous lph from the Cat MPD to feed some Maretron interface, which does the math based on the boat speed to eventually show the lpm?

That aside, I for one would be interested to hear more about the Maretron components required, and possibly their ballpark costs.