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Old 04-17-2013, 04:59 AM   #1
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Hi!


Does anyone have knowledge of where I could find a decent fuel burn chart form my engines? I have been using the one found in a brochure but it is a scanned version and not that clear to read. I also have all the manuals and repair books but none of them really contains the data.

So far I know that at cruise I burn roughly 60 L/hour with both engines 2700 rpm. But being the analytical guy I am I'd like to play with the figures and right now my excel looks to be slightly off, because I cant read the figure that clearly.

I will do some measuring when the boat is splashed but it will take couple of months before that happens.
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Old 04-17-2013, 05:57 AM   #2
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Wouldn't the actual fuel burn depend a great deal on the size, shape, and weight of the boat the engines are in?

I think you need to find a way to accurately measure the amount of fuel you are burning at a given instant and then run the boat at several different (GPS) speeds over still water with calm winds to get anywhere near an accurate fuel burn figure.
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Old 04-17-2013, 06:26 AM   #3
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You are right, it would depend on those factors. I will do the measurements when given the opportunity.

So far I have done the spreadsheet so that I have the power/rpm and the consumption mapped out with roughly accurate boat speed (out of memory). It is interesting to see the consumption vs. Speed and see how the miles per litre figures react to various rpm's. I'm not saying it is accurate but so far it has reassured me that in a halfplaning hull there are some speeds that I would not want to use (not aurpricingly).

The graph I'm using is not readable enough to get accurate figures, hence the question.

I like to crunch numbers and draw graphs, at least it gives me some info to try different rpm's in order to gain the most efficient low and high cruise speeds. Knowing the baseline curve for the engine gives just that, a baseline...
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Old 04-17-2013, 06:46 AM   #4
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Volvo Penta's website has downloadable data sheets on most legacy engines. I have one for the TAMD40B that I found there. If you can't find it, send me a PM with your email address and I will send it to you. The curves are small however, but it is a decent quality pdf- about 1 MB.

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Old 04-17-2013, 07:15 AM   #5
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Thanks..


If the chart is on the left hand corner of last page I have the same datasheet, also downloaded from the Volvo site..
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Old 04-17-2013, 10:03 AM   #6
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As has been mentioned, there are a lot of factors to be considered, but your fuel consumption seems high.

I have a TAMD40A, which is not quite the same engine, but similar, in a 11,600 pound 32 foot semi displacement vessel.

At 2600 RPM I burn 10 litres/hour which gives me a speed of 7.5 knots.
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Old 04-17-2013, 10:30 AM   #7
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At 2700 rpm she gets to around 16,5-17,5 knots and according to the previous owner she should do around 2,5 L/Mile, this is of course with both engines running. I know that I'm not too far from that figure, but please bear in mind that the combined 60 L/hour is a trip planning average that contains low speed cruising and idling. It is calculated from refills.

That figure also contains the uneven fuel burn, the sb engine was always thirstier than the other. The difference was around 8% last summer. This is what I hope to be fixed by my current injector overhaul (those were mighty dirty and propably leaking a bit). Maybe my bottom job will also help...

Oh, the weight of the boat is around 6500 kg. Gets correct WOT
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Old 06-26-2013, 12:14 PM   #8
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First filling for this season, so it is number crunching time.

121 liters to tanks and so far we have covered 56 miles (been busy with the kids), I believe that totals to somewhere around 2,16 liters per nautical mile.

Some idling around the dock, speed limit zones and cruising. Including few mad dashes of the "Italian tune up" for few minutes at a time. Rpm most used have been 2800 and 1400...

Maybe this is the bottom job paying for it self or could it be the redone injectors (difference between tanks was only 3 liters)...
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Old 08-24-2016, 04:27 PM   #9
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Quote:
Originally Posted by djmarchand View Post
Volvo Penta's website has downloadable data sheets on most legacy engines. I have one for the TAMD40B that I found there. If you can't find it, send me a PM with your email address and I will send it to you. The curves are small however, but it is a decent quality pdf- about 1 MB.

David
Good Afternoon. i have just recently purchased a 1986 CML 37 with twin TAMD 40B's. If you still have the data sheets for consumption, I would love to have a copy. thanks.
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Old 08-25-2016, 06:27 AM   #10
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Its far easier to find a set of plans for a T-88 nuke weapon than get a BMEP or fuel map from a engine mfg.

The usual HP/prop graph has almost no use for deciding on engine/tranny and prop choices.

A Flow Scan will do a great job on an existing boat to decide operating speeds vs fuel burn.
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Old 08-25-2016, 05:00 PM   #11
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Originally Posted by MBCML View Post
Good Afternoon. i have just recently purchased a 1986 CML 37 with twin TAMD 40B's. If you still have the data sheets for consumption, I would love to have a copy. thanks.
PM me with your email address and I will send a copy.

Also for the OP, boatdiesel has an advanced prop calculator that lets you input known performance data, selects a hull type that gives that performance and then plots rpm vs power and fuel burned. It uses more realistic power values derived from your hull type rather than the simplistic exponential prop curve shown on diesel manufacturer's data sheets.

Great for a number crunching geek!!

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Old 08-26-2016, 07:14 AM   #12
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Quote:
Originally Posted by FF View Post

A Flow Scan will do a great job on an existing boat to decide operating speeds vs fuel burn.
I agree FF, without a Flow Scan most calculated figures can be grossly inaccurate and misleading. Wouldn't want to plan a long trip around them.

I have a TMD40A and run it at 2100 RPM at 7 knts. It sure doesn't break the bank. We were on a trip this month with 3 other boats, 2 gas powered, and I used a third of the fuel that they did at the same speed.
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