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Old 11-12-2013, 01:13 PM   #141
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Greetings,
Yup, hot fuel 'll do it to ya...
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Old 11-12-2013, 01:20 PM   #142
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That's a good pair ... care to document those claims?

Let me get this straight ... if I supply the pump with 100F fuel it will double the temperature when it reaches 1000psi? Is that what you are saying? What temperature does the fuel reach when it reaches the typical pressure at which a typical mechanical injection pump operates? Do you know what pressure that is? It should be pretty easy for you to document that temperature rise as well. How about getting back to us with that would you, please?



You'll have to explain to me why that engine room is hotter than the little recrational boats that don't have substantial supply and exhaust fans and one heck of a lot less volume. have you ever been in a working engine room?



Sounds like a bunch of strange people who don't have much experience in real life marine operations.
Yes, that is correct. Building pressure builds heat. This is a proven fact. Hydrolics built heat when used, turbo's built heat building boost. Put a heat gun on the injector lines, they will be considerably hotter than the pre-lift pump fuel line. It's the whole principal behind the compression ignition or diesel engine.

Pop pressure is different in different engines. I've seen from 600psi to over 30,000 psi. Depends on the system used.

Well, the retired shrimp boat I had looked at had 2 drive engines, 2 large gensets, 2 large hydro pumps all running, plus a back up genset and hydro. Big engine room, but stuffed full of running heat factories. Now, you are correct when you mention "little" engine rooms. I did not think of something small, smaller than walk in with standing head room doesn't interest me, so I wrote that off. Still shouldn't be bad if there is proper airflow. If not, it's a bad designed boat.


They are recognized as the best cummins engine rebuilders in the country. They worked with cummins to fix flaws with the common rail's before they were on the market. But, unlike the average sub par tech, they won't turn out an engine that isn't right. You should see the clean rooms where they build engines. Perfectionism at its best. Not some dirty shop, filling new engines with crud. People may "wash out" an engine, but that is the wrong way to do it. That is the mark of a sub standard mechanic. Think of it as, just because your friends are jumping off a cliff, should you do it too? The wrong way may work sometimes, but that still doesn't make it right. Of course, if all pleasure boat owners are as willing as you to do things the wrong way just to save a buck, I will believe boats are horribly owner abused. I would have thought that a major investment like a boat would draw people who considered it an investment and maintain it properly. I'm glad I am looking for an old hull and intend to rebuild everything myself. Properly.
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Old 11-12-2013, 01:33 PM   #143
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And a quick clarification. I am likely quite alone on my disdain for these engines. There is a lot of "smoke" blown around about them. My ass just isn't that keen on inhaling it.

And one more thing...it is just FYI. According to Mr. Athens, the 6BT pumps 4 times more fuel than it uses. My tanks are relatively small(100 gals). At cruise each engine is burning about 8-10gph. If the temp doubles at each go round, I would explode in just a few hours.
You would be surprised how much temp goes away when pressure drops. Fuel lines take heat out. A relatively small amount of heated fuel goes back. Most of the return fuel never sees full pressure and heat. It is excess to make sure the pump is properly supplied and doesn't cavitate.
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Old 11-12-2013, 02:18 PM   #144
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Geez, I wonder why waterjet cutting machines don't produce great clouds of steam, or melt the crap out of fabrics, paper, or foam? Some of those buggers squeeze water up to around 100,000psi. Must be some kind of voodoo thing, do you think?

Hydraulic systems get hot because flowing oil through an orifice will increase the heat. It is a liquid with long molecules that release a lof of energy when they get disturbed, it's not a gas that expands by absorbing heat from outside or converting the work of compression into pressure and heat. If you have a 100 hp worth of hydraulic flow but only extract 50hp worth of work out of it, that other 50hp is going to be dissipated as heat.

Check out the temperature difference across a hydraulic reducing valve sometime ... the pressure drops drastically but it doesn't cool the fluid - quite the opposite, it gets hotter than a trawler forum argument with a pretender. Dropping pressure in a hydraulic system without doing work will produce heat. The pump only adds a tiny amount of heat from internal friction. The fluid does not compress enough to produce heat adiabatically.

Compressing a gas is a whole 'nuther process altogether and that is how a diesel engine works and why air gets hot when compressed by a turbocharger. Like many others with a little bit of the vocabulary, you need to attach the correct concept to the words if you want to make sense or try to explain how or why stuff works.

You've got quite a handly little IR thermometer if it can read an injector tube by itself. Tell you what I'll do, sometime in the next week or so I'll take an IR movie of fuel moving through a diesel injection pump so we can see how much it heats up.
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Old 11-12-2013, 02:31 PM   #145
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Most of the return fuel never sees full pressure and heat. It is excess to make sure the pump is properly supplied and doesn't cavitate.



Would you be so kind as to supply a fuel system diagram for a Cummins engine that shows where the return fuel originates?
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Old 11-12-2013, 02:43 PM   #146
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Most importantly by bringing the engine(s) to operating temp burns off any condensation inside the engine.
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Old 11-12-2013, 03:02 PM   #147
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Some of you guys are talking past each other.

Compressing diesel does increase its temperature significantly But temperature is not straight away heat. Heat has another dimension per pound or per gallon or per something. So if you have high temperature and low volume or mass then you don't have so much heat. Conversly with reletively low temperature and a large volume you can have a lot of heat to deal with. Another point is that the hotter something is the faster it will give up its heat to something else. Enough of the thermodynamics. It is important to note that the return fuel on a diesel engine is hot from both compression and where its been and it has provided some lubrication to system.

O.B. Thomas, P.E.
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Old 11-12-2013, 03:52 PM   #148
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Some of you guys are talking past each other.

Compressing diesel does increase its temperature significantly But temperature is not straight away heat. Heat has another dimension per pound or per gallon or per something. So if you have high temperature and low volume or mass then you don't have so much heat. Conversly with reletively low temperature and a large volume you can have a lot of heat to deal with. Another point is that the hotter something is the faster it will give up its heat to something else. Enough of the thermodynamics. It is important to note that the return fuel on a diesel engine is hot from both compression and where its been and it has provided some lubrication to system.

O.B. Thomas, P.E.
Now you really are talking past the subject. We are not talking about the number of BTU's transferred to the fuel in the injector pump plunger, the Texan stated that the temperature - the sensible temperature - of diesel fuel was doubled when pressurized to 1,000 psi and the temperature of the fuel lines was measured at twice that of the incoming fuel, that temperature rise being the result of compressing the liquid and producing a temperature high enough to raise the temperature of the fuel lines.

Not quite enough thermo in my opinion. The return fuel is hot because it is used to extract heat from friction within the injection pump and from the injectors within which it circulates. If you can show the math or by empirical evidence that liquid fuel is heated "significantly" by compression in the injection pump I will eat that crow but I am not going to worry too much about how much bird sauce I need to stock up on.

I believe that if you research it a bit further, increasing the pressure of diesel fuel at a couple of psig to 30,000psig at 40C will raise the temperature to about 45C ... with a specific heat of about half that of water I seriously doubt that the miniscule flow of fuel is going to rise the temperature of the lines to 80C by adiabatic compression. Increasing the pressure rapidly to 1,000 psig doesn't even register on any scale.

Like I offered, give me a bit of time to set up and I will provide an IR movie to show what gets hot at what rate when a diesel engine is fired up from ambient. The injector lines are not even on the real world map.
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Old 11-12-2013, 04:32 PM   #149
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Like I offered, give me a bit of time to set up and I will provide an IR movie to show what gets hot at what rate when a diesel engine is fired up from ambient. The injector lines are not even on the real world map.
Now THAT I would like to see!!!
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Old 11-12-2013, 05:35 PM   #150
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Gentlemen,

While I find your intercourse somewhat entertaining (I keep waiting for the knock-out punch), I am finding it difficult identifying the relevance to my initial inquiry.

As I’m reading the posts I'm trying to determine what is fact, and what is opinion, (except Rick B, he tells you when it’s his opinion) or just plain fiction. It’s seems everyone speaks from a position of knowledge and yet there are some very opposing statements.
For my part, I have to sift through all the banter and try to extract something useful, but man, you guys don’t make it easy.

I don’t own Cummins engines. I saw a couple of brand new ones on pallets in a boat yard and they sure looked pretty slick. Apparently some guy was pulling his Hino’s out and putting those in.

It’s ok with me if you guys want to continue this UFC thing; I just thought I’d mention that you’re going down a different waterway.

I would love to see the movie too. Do we have to wear those funny glasses to watch it? KJ
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Old 11-12-2013, 05:42 PM   #151
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Rick and a few others alluded to it...if you start your engines once a week or so...get them up beyond a cold idle and you are probably OK...you are probably OK to NOT run your engines for months if the oil was changed and you block off the exhaust and intake openings to reduce the moisture in the engine while it sits.

Either extreme is probably bad...a start and oil pressure with no temp increase and shutting them down on a regular basis or letting them sit for years without a prescribed "long term storage" procedure. Short of those and reasonable knowledge covered here and the chances your engine will die of something else is probably true.
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Old 11-12-2013, 06:24 PM   #152
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Hey I have a solution reference the OP's topic. And it is a "knock out" punch. Everyone get their pen and paper so they can write it down. Two words:

Block Heaters!!!!

THE END!

And reference all of the other banter....I announced my "opinion" when I voiced it. I also provided a random sample to support my argument. Factual data.

One more thing for SomeTexan. If you know 6BTs and their marine application so well, there is a market out there and money to be made. Right now, Seaboard Marine owns it!!! Before you bestow upon us your expertise, I would challenge you to educate yourself on all things Cummins Marine!!! Tony Athens has been kind enough to document his life of experiences with these engines and share them with us. Again, if you care to read up on the MARINE side of these engines please go to this link and be enlightened.

Tony's Tips - Information about Marine Diesel Engines and Boats from Tony Athens
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Old 11-12-2013, 07:02 PM   #153
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Two words: Block Heaters!!!! THE END!
Block heaters work great on my standby generators. Two 1 megawatt Cats sitting on a tank with a days supply of diesel, 1650 gallons of it. From not running to 1800 rpm full load in less than 10 seconds. Darn things will even send me an email when they want something
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Old 11-12-2013, 07:14 PM   #154
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Thanks for this link, some very helpful information there.

-Mike (a 'happy' Cummins owner)
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Old 11-12-2013, 08:07 PM   #155
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As Iím reading the posts I'm trying to determine what is fact, and what is opinion ... (except Rick B, he tells you when itís his opinion) or just plain fiction.
That's just because I'm such a fair and reasonable kind of guy ...
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Old 11-12-2013, 08:15 PM   #156
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Greetings,
"That's just because I'm such a fair and reasonable kind of guy ..."

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Old 11-12-2013, 08:45 PM   #157
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RickB, 1, you would be surprised how much heat is added by the injection pump. Compressing anything creates heat. When you are talking over 1000psi, doubling temp isn't uncommon. But, it's under pressure, it won't vaporize.
The compressibility of gasses is described by the ideal gas laws pv=nrt. The laws for fluids are different due to the fact that the molecules are closer and not moving at speeds defined by van der walls equations. W/o getting into a physics discussion ponder this link for a while if you choose and then perhaps we can all decide whether to start or pickle an engine for the winter. http://www.chem.purdue.edu/gchelp/liquids/teffect.html btw you have made some great contributions to this discussion.

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Old 11-13-2013, 06:54 AM   #158
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Now THAT I would like to see!!!
It might be a couple of days before I can arrange a cold engine to video but in the meantime, take a look at these photos of a running engines.

One pic shows the IR view, the other shows the visual image of the same photo.

Note that the temperature of the injection pumps and fuel lines are (for practical purposes) no greater than the parts they are attached to. The pumps certainly add a degree or so but that is to be expected of any operating machine with moving parts. The hot bright background is a generator engine that has been running for several hours.

The smaller engine is a generator that has been running for several hours at about twice the rpm as the main engine.

I will let the temperatures speak for themselves.
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Old 11-13-2013, 07:58 AM   #159
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A cold front rolled through last night it is 37* here.
I had to laugh early this morning when I heard an announcer on tv telling folks it is not a good idea to let their car engines idle to "warm them up" that they may be damaging the engine by doing so. HERE WE GO AGAIN!
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Old 11-13-2013, 08:54 AM   #160
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Our ancient DD 6-71 flows large amounts of fuel to cool the injectors, which ARE the injection pump on a DD .

The tanks are small 100G each , and with a flow scan can operate with 90G used then switch.

As we cruise at 3GPH or less the last 10G in the tank may have been thru the engine 200 times .
The tank does get warm , but one can still hold a hand to it , so as guess would be below 125F , where hurt starts.

Using fuel as injector or injector pump cooling is no big deal as the injection pump is at engine operating temp, usually under 200F.

The huge surface area of most tanks is great for cooling , tho I do not know how well a modern plastic tank, foamed in place would fare.
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