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Old 08-23-2013, 10:17 AM   #1
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Cat Fuel Burn?

Can anyone help me out with this. I am trying to see what the fuel consumption is on this engine Caterpilla 3406.

I found this chart, but can't figure out how to read it.

This is the performance of the boat:

500 RPM Speed 4.0 Knots
860 RPM Speed 5.5 Knots
1000 RPM Speed 6.7 Knots
1200 RPM Speed 7.2 Knots
1400 RPM Speed 8.0 Knots
1500 RPM Speed 8.2 Knots
1600 RPM Speed 8.8 Knots
1700 RPM Speed 9.0 Knots
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Old 08-23-2013, 10:24 AM   #2
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The chart refers to SHP (shaft horse power). The fuel burn function is related to the power (SHP) needed to move the boat at a certain speed.
Different for different types of boats, displacements, hull shapes etc. There are some general rules of thumb that probably under-estimate the consumption but you really need information related to your vessel.
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Old 08-23-2013, 10:29 AM   #3
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Quote:
Originally Posted by Chrisjs View Post
The chart refers to SHP (shaft horse power). The fuel burn function is related to the power (SHP) needed to move the boat at a certain speed.
Different for different types of boats, displacements, hull shapes etc. There are some general rules of thumb that probably under-estimate the consumption but you really need information related to your vessel.
Oh, ok. Thnx.
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Old 08-23-2013, 12:03 PM   #4
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The table on page 1 shows specs for three versions:
- turbocharged and aftercooled (TA, 265 continuous shaft HP, 15.4 GPH at 1800 RPMs)
- turbocharged (T, 240 SHP, 13.1 GPH @1800)
- turbocharged (T, 225 SHP, 12.0 @ 1800)

Looks like curves G and J from the fuel burn charts apply:
- TA/265 - approx. 13? GPH @ 1500 RPM
- T/240 - approx. 10.5? GPH @ 1500
- T/225 - approx. 9.5? @ 1500

(Those same curves also illustrate fuel consumption from the page 1 chart when at rated HP at 1800 RPMs.)

And from your performance chart, 1500 RPMs should be giving you approx. 8.2 kts +/- and depending on load, wind, tides/current, sea states, etc.

Useful to know which of those three engine variations you'd actually have.

-Chris
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Old 08-23-2013, 01:10 PM   #5
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I was told by a diesel mechanic as a "general rule" with marine diesel engines, for every 100hp used figure about 5GPH. So if you have a 375hp 3208 T/A and you are using 200hp of that engine you would burn about 10GPH. You still have to factor weather, current etc.
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Old 08-23-2013, 02:13 PM   #6
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Quote:
Originally Posted by ranger42c View Post
The table on page 1 shows specs for three versions:
- turbocharged and aftercooled (TA, 265 continuous shaft HP, 15.4 GPH at 1800 RPMs)
- turbocharged (T, 240 SHP, 13.1 GPH @1800)
- turbocharged (T, 225 SHP, 12.0 @ 1800)

Looks like curves G and J from the fuel burn charts apply:
- TA/265 - approx. 13? GPH @ 1500 RPM
- T/240 - approx. 10.5? GPH @ 1500
- T/225 - approx. 9.5? @ 1500

(Those same curves also illustrate fuel consumption from the page 1 chart when at rated HP at 1800 RPMs.)

And from your performance chart, 1500 RPMs should be giving you approx. 8.2 kts +/- and depending on load, wind, tides/current, sea states, etc.

Useful to know which of those three engine variations you'd actually have.

-Chris
I think you are reading the max or continuous output curves and you should be looking at the PDC and PDX (Prop demand curve) curves. These are only approximations with a typical propeller, and as you say every boat is different. But if you look at the prop demand curve for the 265HP engine at 1500 RPM it's only producing 160HP and burning 7-8gph......
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Old 08-23-2013, 02:30 PM   #7
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Tad is right, the curves where consumption is based on prop demand are the ones to use (PDC & PDX). The propeller does not use full available HP, and fuel, except at WOT assuming the vessel is propped the way the engine mfg. specifies.
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Old 08-23-2013, 03:35 PM   #8
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Tab is 100% right. You need to get the fuel burn spec sheet for your power plant. This is the spec sheet for a C-7 454 hp. You can go online and find one for your power plant, or better yet, you can email Caterpiller and the will sent it to you.

But due keep in mind, these spec sheet are just a base line. There are many factors to fuel burn as these Gents have pointed out.

In any case. All the best to you

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Old 08-23-2013, 03:38 PM   #9
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At hull speed. 7.2 knt's. My cat 3208 n.a. 210 hp. Burns about 1 gallon per 4 nautical miles. As measured by a floscan.

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Old 08-23-2013, 03:42 PM   #10
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You can go online and find one for your power plant, or better yet, you can email Caterpiller and the will sent it to you.

H.Foster
Have the CAT email address?
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Old 08-23-2013, 03:43 PM   #11
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P.S.

I forgot to say this as well. If you have twins power plants and when you look at the fuel burn spec sheet you need to double the GPH. You are after all running 2 power plants. And also do not forgot about the fuel you will burn running your gensets as well. You can get those spect sheet as well.

All the best
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Old 08-23-2013, 05:05 PM   #12
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Originally Posted by Tad Roberts View Post
I think you are reading the max or continuous output curves and you should be looking at the PDC and PDX (Prop demand curve) curves. These are only approximations with a typical propeller, and as you say every boat is different. But if you look at the prop demand curve for the 265HP engine at 1500 RPM it's only producing 160HP and burning 7-8gph......

Yes, I was looking at the continuous output curve G and fuel consumption J based on that curve.

Intending to highlight that as a possible approximation of "worst case" (heavily loaded, snotty seas, wind, etc.). But partly also to mate the approximate numbers from the curves to the continuous rating in the table on page one.

So much the better that PDC and PDX indicate lower burn rates during normal ops in benign conditions.

-Chris
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Old 08-23-2013, 06:02 PM   #13
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Thanks guys. I will e-mail Cat and ask for the spec sheet. It is a single engine.
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