Diesel engine questions
Why do diesels get better mileage and last longer than gas engines?
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'cos there running in oil,(lubrication) as a fuel & not as a detergent, washing the lub away & scrubbing metal 2 metal !![;)] 0 -
In the case of the turbo diesel, as the turbine packs more air into the engine, the same amount of fuel is used. So that, the engine is burning the same amount of fuel as a non turbo, and it is getting the extra power from the oxygen, thus more power and better mileage.
With a gasoline turbo, as the turbine packs more air into the engine, there must be a similar increase in the amount of gasoline injected. You get lots more power, but a decrease in fuel economy.
Why the diesel lasts longer, I don't know.0 -
A factor on lasting longer partly is that most diesel motors operate at a little lower rpm. 0 -
A gas engine that is fueled by LP last longer and is a much cleaner fuel. LP has less power thought. Why doesn't AL Gore push LP over gasoline? 0 -
Diesel's last longer because of a combination of things....
1 - as GRD said, they typically operate at low RPMS, they produce massive amounts of torque at low rpms, and even when towing, the engine doesn't need to rev as high to accelerate.
2 - same as Mond said. Diesel is actually an oiled fuel. The oil in the fuel gives added lubrication, when the typical gasoline engine is started from a dead cold, there is no lubrication. In a second the oil pump has pumped and recirculated the oil around to lubricate the needed parts. Since diesels burn the oil fuel, there is available lubrication from the start. Cylinders, pistons, and rings are not subjected to "dry starts" like with gasoline motors.
3 - Diesels do not have ignition systems. They have glowplugs to intiate starting, once the motor is started the fuel air mixture is ignited by a process called dieseling(thus diesel). The mixture is compressed to the point of ignition. Some diesels have compression rations of 23+:1. The fact that there are no ignitions systems is another reason for their reliability.0 -
Cubs reason number 3 is why they are more efficent. Firing with compression causes it to fire all at once and not at one point like with spark plugs. You get a better spark all though the fuel and all of it is done at once. 0 -
quote:Originally posted by PC800
Why do diesels get better mileage and last longer than gas engines?
now you/we have an idea of why it does what it does, Can anyone here tell me why it cost more at the pump than gas. at least up until the last week or so diesel has been 10-20 cents more per gallon. now here where i am diesel i 10 cents less a gallon.
here are a few reason's Why, I ask,
1. it take's the same amount of oil to make a gallon of diesel as it does gas
2. the refining process is much less complicated and time comsuming
3. the are less additives that must go into diesel than gas
SO WHY,0 -
Since they've gone to this Bio-Diesel(cleaner), the prices have gone up slightly. It's usually high when gas is low or the other way around.
Refining costs have gone up for this new Bio-Diesel.0 -
quote:Originally posted by Odawgp
quote:Originally posted by PC800
Why do diesels get better mileage and last longer than gas engines?
now you/we have an idea of why it does what it does, Can anyone here tell me why it cost more at the pump than gas. at least up until the last week or so diesel has been 10-20 cents more per gallon. now here where i am diesel i 10 cents less a gallon.
here are a few reason's Why, I ask,
1. it take's the same amount of oil to make a gallon of diesel as it does gas
2. the refining process is much less complicated and time comsuming
3. the are less additives that must go into diesel than gas
SO WHY,
Doesn't here. Diesel prices are as much as $.30 less than gas in northern Wisconsin.0 -
Because a diesel is compression-ignition rather than coil-ignition, when the mixture fires (all at once, as stated) the stresses to the bottom end of the engine are much higher than a gas engine. So, the engine must be more robust to absorb the high impact loading.
Anyone remember the GM diesels of the late 70s-early 80s ? These were built on a gas engine block and could not handle the extreme loads. They almost all failed, and, if I recall, GM had some sort of generous buy-back program at the time.
As far as the price goes, there are two issues - supply and demand tends to keep prices up. I would guess that there is far less than 10 percent of crude refined into diesel fuel, than gas. The second issue is the actual complexity of the refining process. Diesel comes out of crude near the bottom of the catalytic cracking process, while more volatile liquids need to come off nearer the top of the cat-cracker tower. That creates a lower cost per gallon to manufacture. Also, it does take more crude oil to produce a gallon of gasoline than a gallon of diesel.
As far as the improved economy goes, the sudden ignition of the fuel, which would be called "spark knock" or "detonation" in a gasoline engine, occurs at much lower piston speeds and higher manifold vacuum (in non-supercharged applications) than gas engines, producing maximum torque at much lower RPM. Torque, as you may know, is what moves the vehicle, and horsepower is a factor of torque and RPM. Maximum torque in an electric motor is produced at full-throttle stall - ZERO RPM.
I have never seen the numbers, but I suspect that, in terms of overall cost, diesel and gasoline engines come out nearly equal, in a light truck or automobile. I'm talking about the increased cost of the engine(system) and drivetrain and much higher maintenance cost, over the life of the vahicle.
That increased overall cost, and lack of acceleration performance, is probably why diesels don't have nearly the popularity of gasoline fueled light trucks and automobiles. A diesel can be tuned to perform as well as a gasoline engine, but, the fuel economy would be the same, or the diesel would be even costlier.
How's that ??
Doug0 -
Well... Gentlemen & Ladies
Some of you came close, but no cigar!
Here's the skinny on diesel vs. gasoline engines.
We'll start with energy content per volume of fuel. Remember the LP comment? LP has less energy content by volume than gasoline. Alcohol also has less energy by volume than gasoline. Both burn cleaner, though. Either will extend the life of a gas engine.
Diesel fuel, on the other hand, has more energy stored in a like volume of fuel. Thus, if diesel contains 30% more energy by volume of fuel, it stands to reason that fuel economy will increase by 30% (in theory anyway).
Diesel engines do not ALL have glowplugs. Glowplugs are merely a convenience for starting a diesel engine. Look at Cummins for example.
Spark or compression ignitions have more to do with the type of fuel being used than anything else. Then there's a matter of cetane and octane, but that's a discussion for another time.
Turbo induction on either diesel or gas does exactly the same thing. It allows more fuel to be burned. Thus more power from a given displacement. Too much fuel in a non-turbo diesel and you'll get lots of black smoke. Too much fuel in a gasser and she'll stall.
Lubrication... A wives tale about the lubricity of diesel fuel. Nothing more fatal in a diesel than what we call a fuel wash at startup. VERY BAD!
Longevity... Don't add enough octane or overboost a gasser and you'll get "spark knock". That's really just violent compression ignition caused by the explosion of the mixture instead of an even burn. Spark knock will destroy a gasoline engine.
Diesels thrive on "exploding" fuel. They don't rely on a smooth flame front and are built heavily enough to withstand the stress of compression ignition.
So... Longevity has to do with the fact that diesels are much more heavily built than gassers. Don't believe me. Just refer to the efforts GM made to convert their gasser V's to diesel. They found out very quickly that it didn't work.
Oh... The stronger the components the more they weigh. The more they weigh the more the revolving mass. The more the revolving mass the more torque produced. But... The heavier the reciprocating mass the less rpm's allowable.
Want to get into 2-stroke diesels? I'm game.0 -
Nord - I'm pretty sure that diesel has LESS energy stored per volume of fuel. The energy comparison would be by comparing output per volume, in BTUs.
Doug.
* edited to refine my reply0 -
quote:Originally posted by Doug Wilson
Nord - I'm pretty sure that diesel has LESS energy stored per volume of fuel. The energy comparison would be by comparing output per volume, in BTUs.
Doug.
* edited to refine my reply
Doug... you are wrong in your belief. All fuels are measured by BTUs (Basic Thermal Units) per pound. Diesel fuel is much denser than gasoline, and therefore, it has considerably more BTUs per pound than gasoline.0 -
Here you go - http://auto.howstuffworks.com/diesel3.htm 0 -
Thanks, Bert. I hate it when I don't get my facts straight !!
Everything else OK ??
Doug0 -
quote:Originally posted by nord
Want to get into 2-stroke diesels? I'm game.
Detroit Diesel did this long, long, ago. They will make some sick horsepower. EPA put the design out of business. They were noisy smoky beasts. Still a few running around my area. the is a 4-71 (4 cylinders, 71 cubes per cylinder) at running a sawmill a mile or so away. Most I have seen were 2-71's, 3-71's, 4-71's, and 6-71's. IIRC there were some 53 inch versions and some 8 and 12 cylinders too.0 -
quote:Originally posted by Zulu7
quote:Originally posted by Odawgp
quote:Originally posted by PC800
Why do diesels get better mileage and last longer than gas engines?
now you/we have an idea of why it does what it does, Can anyone here tell me why it cost more at the pump than gas. at least up until the last week or so diesel has been 10-20 cents more per gallon. now here where i am diesel i 10 cents less a gallon.
here are a few reason's Why, I ask,
1. it take's the same amount of oil to make a gallon of diesel as it does gas
2. the refining process is much less complicated and time comsuming
3. the are less additives that must go into diesel than gas
SO WHY,
Doesn't here. Diesel prices are as much as $.30 less than gas in northern Wisconsin.
here in the rockie's we have been paying 10-20 cents more per gallon of diesel than gas for the last 3 yrs at least. there was a time about 4yrs ago that diesel was 50 cents less a gallon but now even OFF ROAD RED diesel (which is minus all the FED hwy tax.) is the same price as a gal of regular gas.
Glad to hear you all aren't getting the SHAFT.0 -
quote:Originally posted by Odawgp
quote:Originally posted by Zulu7
quote:Originally posted by Odawgp
quote:Originally posted by PC800
Why do diesels get better mileage and last longer than gas engines?
now you/we have an idea of why it does what it does, Can anyone here tell me why it cost more at the pump than gas. at least up until the last week or so diesel has been 10-20 cents more per gallon. now here where i am diesel i 10 cents less a gallon.
here are a few reason's Why, I ask,
1. it take's the same amount of oil to make a gallon of diesel as it does gas
2. the refining process is much less complicated and time comsuming
3. the are less additives that must go into diesel than gas
SO WHY,
Doesn't here. Diesel prices are as much as $.30 less than gas in northern Wisconsin.
here in the rockie's we have been paying 10-20 cents more per gallon of diesel than gas for the last 3 yrs at least. there was a time about 4yrs ago that diesel was 50 cents less a gallon but now even OFF ROAD RED diesel (which is minus all the FED hwy tax.) is the same price as a gal of regular gas.
Glad to hear you all aren't getting the SHAFT.
Up until several months ago, diesel fuel was about the same price as the mid-grade gasoline (and had been for the past few years). Then about three months ago, gasoline prices rose, but the diesel fuel price did not, and even the regular (87 octane) gas was suddenly more $$ than diesel. The price gap between the two has been steadily increasing over the last several months, and currently, I am paying $2.89.9 per gallon for diesel, and regular grade gasoline is $3.41.9 per gallon... a whopping $.52 per gallon difference[^][8D][^].
Now, considering the fact that my Cummins TD powered Dodge Ram 3500 averages 19.6 mpg, I am laughing my butt off at the people who insist on driving gasoline powered trucks[:D][:D].0 -
Here's a set of energy charts for several different fuels. All deal with an "average" type of course, and individual fuels can differ a bit from the average.
Fuel & Energy
Conversion & Equivalence Chart
Electricity:
1 KW = 3,413 Btu/hr
Natural gas:
1 Cubic Foot of Natural Gas = 1030 Btu's
1 CCF = 100 Cu Ft = 1 Therm = 103,000 Btu's
1 MCF = 1,000 Cu Ft = 10 Therms = 1,034,000 Btu's = 1.034 MMBtu's
Propane:
1 Gal Propane = 91,600 Btu's
1 Cu Ft Propane = 2,500 Btu's
Gasoline:
1 Gal Gasoline (mid grade) = 125,000 Btu's
Ethanol:
1 Gal Ethanol = 76,000 Btu's
Fuel Oil:
1 Gal of #2 Fuel Oil = 139,000 Btu's
1 Gal of #4 Fuel Oil = 145,000 Btu's
1 Gal of #6 Fuel Oil = 150,000 Btu's
1 Barrel of Oil = 42 Gallons
1 Btu = 252 calories
1 Btu= .293 watt
1 ton of refrigeration = 12,000 Btu/hr
1lb residential garbage = 2,500 Btu
1lb coal = 12,000 Btu
1lb wood = 3,500 Btu
1hp = 746 watts
1hp = 33, 479 Btu/hr (boiler)
1hp = 33,000 foot-lbs./min
1hp = 42,440 Btu/min.
1 watt = 3.412 Btu
1 kilowatt = 1,000 watts
1 kilowatt = 1.341 horsepower
1000 kilowatts = 1 Megawatt
All of the following fuels are equivalent to 1,000,000 Btu's.
Electricity 293.083 kWh
(3412 Btu/kWh)
Natural Gas: 1 MCF, 10 therms or 1,000 cubic feet
Coal: 83.34 pounds
@ 12,000 Btu/pound
Propane 10.917 gallons
@ 91,000 Btu/gallon
Gasoline 8.0 gallons
@125,000 Btu/gallon
Fuel Oil #2 7.194 gallons
@ 139,000 Btu/gallon
Fuel Oil #6 6.67 gallons
@ 150,000 Btu/gallon
Wood 285.7 pounds
@ 3,500 Btu/pound0 -
BTU ='s British Thermal Unit[:)] 0 -
Thanks for all the great info. 0 -
Handy stuff. Thank you.
Doug0 -
quote:Originally posted by richbug
quote:Originally posted by nord
Want to get into 2-stroke diesels? I'm game.
Detroit Diesel did this long, long, ago. They will make some sick horsepower. EPA put the design out of business. They were noisy smoky beasts. Still a few running around my area. the is a 4-71 (4 cylinders, 71 cubes per cylinder) at running a sawmill a mile or so away. Most I have seen were 2-71's, 3-71's, 4-71's, and 6-71's. IIRC there were some 53 inch versions and some 8 and 12 cylinders too.
53 series came in 2,3, 4 V6 and V8 versions
71 series came in 2, 3, 4, 6, V8, V12, V16 and V24
92 series came in V6, V8, V12, V16 and I think a V24
149 series came in V12, V16, V20 and V24
Might have missed a couple in there somewhere.
Then there are the big boys, Sultzer, EMD and ALCO, also 2 strokes
EMD commonly found in locomotives, 635 or 720 cubes per cylinder, V8, V12, V16 and V20 (that I have seen)
Odd 2 stroke, FairbanksMorse, 2 pistons in 1 cylinder, 2 crankshafts. Navy liked to use them in submarines. Some laid out flat and some stand up on end.
Sultzer I worked on (I do governor/control work on engines) was an in line 6. Made 10,000 shaft horse power at 90 rpm. When they went to back the ship up, they stopped the engine and ran it backwards, made to work like that.
New 2 strokes are becoming rare, can't make EPA regs, except for the big ship board engines.
Was on a ship doing some work, they cleaned the turbo charger daily by dumping a barrel of stell balls into the hot side. Made a terrible racket and knocked the soot off of the blades. The exhaust stack had a gutter system that caught the ball, they were washed and stored for the next day's cleaning. Turbo was about the size of 2 pickup trucks side by side.
Diesels are built stronger than a gasser cause they have to be to stand the forces of the diesel burning, this in turn makes them heavier and longer lasting than a gasser. Diesels are not really that much more efficient than a gasser but there is a good amount more energy in diesel than there is in gasoline, alchohol, etc.0 -
What about the Fairbanks & Moorse opposing engines? Wern't they diesels?
Got Guns?0 -
But how many B-T-U'S in a B-U-T-T the size of a T-U-B? 0 -
quote:Originally posted by Cutiegirlracing
Cubs reason number 3 is why they are more efficent. Firing with compression causes it to fire all at once and not at one point like with spark plugs. You get a better spark all though the fuel and all of it is done at once.
Actually, no. The proof is when you hear a diesel run...all that "knocking" is ignition.0 -
quote:Originally posted by richbug
quote:Originally posted by nord
Want to get into 2-stroke diesels? I'm game.
Detroit Diesel did this long, long, ago. They will make some sick horsepower. EPA put the design out of business. They were noisy smoky beasts. Still a few running around my area. the is a 4-71 (4 cylinders, 71 cubes per cylinder) at running a sawmill a mile or so away. Most I have seen were 2-71's, 3-71's, 4-71's, and 6-71's. IIRC there were some 53 inch versions and some 8 and 12 cylinders too.
EPA did not kill them...the reluctance to put a better fuel injection system on them did.0 -
quote:Originally posted by A J Christ
Then there are the big boys, Sultzer, EMD and ALCO, also 2 strokes
EMD commonly found in locomotives, 635 or 720 cubes per cylinder, V8, V12, V16 and V20 (that I have seen)
Diesels are built stronger than a gasser cause they have to be to stand the forces of the diesel burning, this in turn makes them heavier and longer lasting than a gasser. Diesels are not really that much more efficient than a gasser but there is a good amount more energy in diesel than there is in gasoline, alchohol, etc.
EMD engines are 645 and 710 series. Tier 2 emissions are no problem...there are 1000 choochoos running around the U.S. and Canada with a Tier 2 710 engine. All of the V16 variety.0 -
One of the major factors of more power at lower RPM's for a diesel engine lies in the chemistry of the fuel. Diesel is a "long chain hydrocarbon"....therefore, it burns a touch slower than other common fuels, which provides a little better efficiency, and a LOT better power and efficiency when they are huffed or puffed (supercharged or turboed). 0
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