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  #16 (permalink)  
Old 04-29-2010, 12:38 PM
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Hey guys, this is fun. As for diesel fuels. Mercedes Benz labeled their diesel engines as OM power plants like OM 615 or OM 617. The OM is a classification as an OIL fired motor. Diesel fuel is taken off at a different point in the cracking tower so it was always cheaper to buy as it was cheaper to make. Kerosene was also classified as JP 4 which as many know was jet fuel used during the Viet Nam era, might still be. I dont remember all the particulars but diesel is a much more efficient form of fossil fuel combustion than gasoline fired engines. It may have been in publications by Robert Bosch, I used to study them a ton during my career. So my engineering friends, splain some more stuff. Automatic transmission fluid is the universal solvent for those that care.
Bill

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  #17 (permalink)  
Old 04-29-2010, 12:42 PM
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Quote:
Originally Posted by ap72
no one in their right mind would use either kerosene nor diesel as a lubricant, can you use it, sure, you can use any fluid. Should you? No. It actually dissolves most accepted lubricants (because it is a solvent).
ap, you are incorrect. Diesel is a lubricating fuel oil. This is the reason why running a REAL solvent, like gasoline, in a diesel engine causes such catastrophic failure in parts such as injection pumps, injectors and the newer high pressure common rail pumps. They have NO other source of lubrication, and run tolerances in to the micron range. Without the lubricating properties of diesel, these parts gall and seize VERY quickly. To deny the lubrication properties of fuel oil is, at best, misinformation, and shows a lack of understanding on how diesel engines and related parts actually operate.
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Old 04-29-2010, 12:54 PM
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Compression ratios in diesels usually start at about 17.5:1 for forced induction, and as high as 22-23:1 for N/A engines. Diesel is fired due to the heat created by such high compression. Any time you compress a gas (with some very few exceptions), the temperature goes up. When the diesel is injected in an atomized form, there is an instantaneous change of state from liquid to gas, and autoignition occurs. This change of state and instant explosion was the reason for the loud, rattling, noise signature of older generation diesels. Newer designs, such as the newer power-strokes and now the common rail designs used by most manufacturers, utilize what is known as pilot injection. The injector pulses a small amount of fuel into the cylinder while the piston is still coming up on compression. This fuel vaporizes with the increasing temperature, but does not auto-ignite. As the temp comes up, a slow burn is initiated, and causes a much faster vaporization and autoignition of the main injection event, thus lowering the "diesel knock" commonly associated with older diesels. This, coupled with very high injection pressures (over 30,000 psi) make the newer diesel engines much quieter, and more efficient.

As well, part of the "more power" associated with diesel fuel is the fact that it contains more latent heat energy than gasoline. And, because it is fired on cylinder heat and relies on that to vaporize, the hotter it runs, the more efficient it gets, within reason. This is why air cooled diesel engines are more fuel efficient than their liquid cooled counterparts. They have their own issues, as well, but that is another discussion.

Last edited by sbchevfreak; 04-29-2010 at 12:57 PM. Reason: spelling
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  #19 (permalink)  
Old 04-29-2010, 01:01 PM
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Quote:
Originally Posted by sbchevfreak
ap, you are incorrect. Diesel is a lubricating fuel oil. This is the reason why running a REAL solvent, like gasoline, in a diesel engine causes such catastrophic failure in parts such as injection pumps, injectors and the newer high pressure common rail pumps. They have NO other source of lubrication, and run tolerances in to the micron range. Without the lubricating properties of diesel, these parts gall and seize VERY quickly. To deny the lubrication properties of fuel oil is, at best, misinformation, and shows a lack of understanding on how diesel engines and related parts actually operate.

In short, diesel has lubricating properties (like any other liquid). My point being that possessing certian properties does not make it a lubricant.

Ford made a 5.0L engine, camaros came with a 5.0L engine, doesn't mean a camaro is a Ford, even though they both have the same 5.0L engine property.

Gasoline DOES have lubriacting properties as well.
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Old 04-29-2010, 01:07 PM
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To use your own point, just because is posses some solvent properties, does not make it a solvent. Diesel is listed as a FUEL OIL. Gasoline has virtually NO lubricant properties, and to claim such is, IMHO, absurd.
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  #21 (permalink)  
Old 04-29-2010, 01:10 PM
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Thats way cool, so then why do diesel engines seem to have such higher torque capabilities for a similar displacement engine over a gasoline fired engine
Bill
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  #22 (permalink)  
Old 04-29-2010, 01:13 PM
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Quote:
Originally Posted by sbchevfreak
To use your own point, just because is posses some solvent properties, does not make it a solvent. Diesel is listed as a FUEL OIL. Gasoline has virtually NO lubricant properties, and to claim such is, IMHO, absurd.
Most pump gasoline does have lubricant additives. Most race gasoline has additives, one of the reason LL100 is avoided is because it has a low amount of lubrication additives.

Out of curiosity what would you define as a lubricating property?
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  #23 (permalink)  
Old 04-29-2010, 02:13 PM
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Quote:
Originally Posted by Bill Adkins
Thats way cool, so then why do diesel engines seem to have such higher torque capabilities for a similar displacement engine over a gasoline fired engine
Bill
It has some to do with the higher compression, but it also has to do with how the diesel burns. Gasoline's effective cylinder pressures exist between 0 and 22-23 degrees ATDC. After that, any additional fuel would be unburned HC in the exhaust because it runs out of air. Gasoline burns quickly, so for a given potential of air/fuel, there is only a limited amount of peak cylinder pressure that can be maintained over the power stroke.

Diesel not only burns slower, but it continues to inject fuel during the first 15-25 degrees of stroke. The only limitation is with how much air you can cram in there during the intake valve opening (which with turbos is only limited by the tensile strength of the head bolts ) The net effect is that for a given amount of BTUs released in the cylinder during a power stroke, the diesel can apply more of its peak pressure for a longer time (and during the middle of the stroke when it has the most leverage on the crank).
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Old 04-29-2010, 02:28 PM
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Quote:
lu·bri·cant   /ˈlubrɪkənt/ Show Spelled[loo-bri-kuhnt] Show IPA
–noun
1.a substance, as oil or grease, for lessening friction, esp. in the working parts of a mechanism.
–adjective
2.capable of lubricating; used to lubricate.
Use lubricant in a Sentence
See images of lubricant
Search lubricant on the Web

--------------------------------------------------------------------------------

Origin:
1815–25; < L lūbricant- (s. of lūbricāns), prp. of lūbricāre to make slippery. See lubric, -ant

from dodgeram.org

Quote:
the VE and VP-44 pumps are fuel lubricated. The "lighter" fuels, such as Kerosene, Jet-A, and JP-5/8, don't lubricate enough.

Quote:
1.oily smoothness, as of a surface; slipperiness.
2.ability to lubricate; capacity for lubrication

That would be several definitions of lubricant, lubricity, ect.

I gain what I have said about the lubricity of diesel fuel from 17 years of learning, training and actual hands on experience, and making my living diagnosing, repairing, and maintaing vehicles, both gas and diesel. It is my job to know the properties of the fluids involve, as the wrong fluid with the wrong properties can and will cause failures. Diesel fuel in an engine application is classified as a lubricating fuel oil.

Last edited by sbchevfreak; 04-29-2010 at 02:36 PM.
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  #25 (permalink)  
Old 04-29-2010, 02:31 PM
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Quote:
Originally Posted by curtis73
It has some to do with the higher compression, but it also has to do with how the diesel burns. Gasoline's effective cylinder pressures exist between 0 and 22-23 degrees ATDC. After that, any additional fuel would be unburned HC in the exhaust because it runs out of air. Gasoline burns quickly, so for a given potential of air/fuel, there is only a limited amount of peak cylinder pressure that can be maintained over the power stroke.

Diesel not only burns slower, but it continues to inject fuel during the first 15-25 degrees of stroke. The only limitation is with how much air you can cram in there during the intake valve opening (which with turbos is only limited by the tensile strength of the head bolts ) The net effect is that for a given amount of BTUs released in the cylinder during a power stroke, the diesel can apply more of its peak pressure for a longer time (and during the middle of the stroke when it has the most leverage on the crank).

Great defintion. Couldn't have said it any better. Also, the rotational mass of a diesel engine also factors in as momentum.
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  #26 (permalink)  
Old 04-29-2010, 02:56 PM
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I guess you could say sand is a lubricant as well then. it a lot of applications it can reduce friction.

I guess that's one way to look at the world- its all lubricants in the right application.
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  #27 (permalink)  
Old 04-29-2010, 03:13 PM
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OK, I like Curtis's explanation. So where can I find text describing that set of facts. There are those here that wont believe it unless it is written, didn't Yule Brener say something like that? You see I truly love to find technical stuff and read and learn from it.
Bill
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  #28 (permalink)  
Old 04-29-2010, 03:26 PM
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best engine builder in my area uses Diesel as the lubricant for honing cylinders.. I'v also used it for that also and it works good
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  #29 (permalink)  
Old 04-30-2010, 10:01 AM
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Quote:
Originally Posted by ap72
I guess you could say sand is a lubricant as well then. it a lot of applications it can reduce friction.

I guess that's one way to look at the world- its all lubricants in the right application.




I guess I must not know what I am talking about. The almighty ap says I am wrong, and since he knows all, I will stop with my information, as I must be incorrect. ap has spoken, so it must be.
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Old 04-30-2010, 10:49 AM
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Geez, AP. Just do a google search. And yes diesel is a lubricant. Why do you think everyone refers to diesels as "oil burners"? I wouldnt say gasoline is a lubricant, but it does serve its purpose in the tank as a lubricant for the fuel pump.
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