• We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.

Why does diesel fuel exist?

The real question is, why does gasoline exist?

Diesel engines are more efficient and typically last much longer than a gasoline equivalent.
 
No, they can't use gasoline. Totally different combustion characteristics. Diesel engines exist because they're superior in almost every way, but gasoline engines can be lighter and tend more towards top-end power, making them better for racing and diesels better for hauling and regular driving.
 
actually, diesel fuel allows for a higher compression ratio than does gasoline, which leads to better efficiency. the US still frowns on diesels because the older diesel technology resulted in heavily polluted exhaust (think old mercedes diesels). today's diesels are much cleaner and many cars (in europe for now) get upwards of 40 mpg using a diesel engine!
 
From my understanding, diesel engines are more expensive and heavy, but diesel fuel will get you more miles to the gallon. A diesel car will be more expensive when you first buy it, but you'll get MUCH better mileage, so the car really pays for itself.

Sure, the engine is a little more expensive to replace, but how often do you replace an engine in a car's lifetime? Diesel cars are superior in almost every way if you're not some crazy racing guy.
 
Originally posted by: kaizersose
actually, diesel fuel allows for a higher compression ratio than does gasoline, which leads to better efficiency. the US still frowns on diesels because the older diesel technology resulted in heavily polluted exhaust (think old mercedes diesels). today's diesels are much cleaner and many cars (in europe for now) get upwards of 40 mpg using a diesel engine!
Click to expand...

VW jetta TDI gets ~50mpg
 
Originally posted by: Fenixgoon
Originally posted by: kaizersose
actually, diesel fuel allows for a higher compression ratio than does gasoline, which leads to better efficiency. the US still frowns on diesels because the older diesel technology resulted in heavily polluted exhaust (think old mercedes diesels). today's diesels are much cleaner and many cars (in europe for now) get upwards of 40 mpg using a diesel engine!
Click to expand...

VW jetta TDI gets ~50mpg
Click to expand...

aye. $$$ <-very good investment ..they are sellign very high now😀
 
Originally posted by: Eeezee
From my understanding, diesel engines are more expensive and heavy, but diesel fuel will get you more miles to the gallon. A diesel car will be more expensive when you first buy it, but you'll get MUCH better mileage, so the car really pays for itself.

Sure, the engine is a little more expensive to replace, but how often do you replace an engine in a car's lifetime? Diesel cars are superior in almost every way if you're not some crazy racing guy.
Click to expand...

Plus a diesel engine is a lot tougher than gas, so you won't HAVE to replace it. Gas cars start crapping out between 200k and 300k depending on how you care for them (obviously there are exceptions), but a diesel will easily double that if you take care of it.
 
Diesels don't have much horsepower. A jetta TDI only has 100hp and needs a turbo to even get that much. However, you can drive it hard all the time and the engine will still last forever. That's why all big rigs have diesels. They need a lot of power all the time. You could but but the engine from a corvette Z06 in a big rig and it would run ok in the short term, but wouldn't last long.
 
Originally posted by: vi_edit
The real question is, why does gasoline exist?

Diesel engines are more efficient and typically last much longer than a gasoline equivalent.
Click to expand...
Because until VERY recently, diesel was incredibly inconvenient. Until the 1990's diesels required glow-plugs and at best a 30 second wait before you could start the engine (some engines required much longer), diesel congeals at low temperatures (I remember as a kid in 1996 or so in Ohio we had a cold snap in the middle of winter and school was canceled for two days because all the diesel in the busses congealed and none would start), diesel engines used to be almost impossible to start at low temps (some semis had small gasoline engines to start their diesel engines during winter), diesels used to emit vast amounts of particulate emissions that caused severe asthma problems (similar to heavy coal emissions), and the NOx emissions from diesels used to be abominable.

It has only been in the past 10-15 years that diesel has become a viable everyday alternative to gasoline and the engines still cost more to produce.

ZV
 
Horsepower is a marketing tool for gasoline engine makers. Torque is where it's at and diesels make torque in boatloads.
 
Originally posted by: Sureshot324
Diesels don't have much horsepower. A jetta TDI only has 100hp and needs a turbo to even get that much. However, you can drive it hard all the time and the engine will still last forever. That's why all big rigs have diesels. They need a lot of power all the time. You could but but the engine from a corvette Z06 in a big rig and it would run ok in the short term, but wouldn't last long.
Click to expand...

Yes, but compare the torque to a gasoline engine with similar displacement. And look at where they hit their power peaks.

A 1.9L Diesel engine in a VW pumps out about 180 ft/lbs of torque at under 2000RPM's. A civic puts out under 115 at nearly 5000 RPM's. The diesel is great around town and for towing. Not so good for 1/4 drag races though. 🙂
 
Originally posted by: Eeezee
From my understanding, diesel engines are more expensive and heavy, but diesel fuel will get you more miles to the gallon. A diesel car will be more expensive when you first buy it, but you'll get MUCH better mileage, so the car really pays for itself.

Sure, the engine is a little more expensive to replace, but how often do you replace an engine in a car's lifetime? Diesel cars are superior in almost every way if you're not some crazy racing guy.
Click to expand...
It's not so much that the fuel gives the engine better mileage (to some small degree it does, since diesel has more energy per unit volume than gasoline, but this is not the main factor), rather the lack of a throttle butterfly is what gives the bulk of the efficiency. A diesel engine has almost no pumping losses. There is an absurd amount of wasted power in gasoline engines from having to pull a manifold vacuum due to the restriction of the throttle butterfly.

ZV
 
Originally posted by: Zenmervolt
Originally posted by: vi_edit
The real question is, why does gasoline exist?

Diesel engines are more efficient and typically last much longer than a gasoline equivalent.
Click to expand...
Because until VERY recently, diesel was incredibly inconvenient. Until the 1990's diesels required glow-plugs and at best a 30 second wait before you could start the engine (some engines required much longer), diesel congeals at low temperatures (I remember as a kid in 1996 or so in Ohio we had a cold snap in the middle of winter and school was canceled for two days because all the diesel in the busses congealed and none would start), diesel engines used to be almost impossible to start at low temps (some semis had small gasoline engines to start their diesel engines during winter), diesels used to emit vast amounts of particulate emissions that caused severe asthma problems (similar to heavy coal emissions), and the NOx emissions from diesels used to be abominable.

It has only been in the past 10-15 years that diesel has become a viable everyday alternative to gasoline and the engines still cost more to produce.

ZV
Click to expand...

All of this is true. It's similar how gasoline turbo engine used to be problematic up until about 20 years ago (and aren't anymore) but most people still believe that they are problematic. But then again, the turbo did save the diesel. 🙂
 
Originally posted by: Zenmervolt
Originally posted by: Eeezee
From my understanding, diesel engines are more expensive and heavy, but diesel fuel will get you more miles to the gallon. A diesel car will be more expensive when you first buy it, but you'll get MUCH better mileage, so the car really pays for itself.

Sure, the engine is a little more expensive to replace, but how often do you replace an engine in a car's lifetime? Diesel cars are superior in almost every way if you're not some crazy racing guy.
Click to expand...
It's not so much that the fuel gives the engine better mileage (to some small degree it does, since diesel has more energy per unit volume than gasoline, but this is not the main factor), rather the lack of a throttle butterfly is what gives the bulk of the efficiency. A diesel engine has almost no pumping losses. There is an absurd amount of wasted power in gasoline engines from having to pull a manifold vacuum due to the restriction of the throttle butterfly.

ZV
Click to expand...

I'd say the higher compression ratio is more of a factor...Carnot cycle.
 
http://www.slspart.com/wmc.html

First we need vivid analogies to describe energy content. The sad truth is no lay person, politician, or most techies can describe the energy contained in a kilowatt hour in simple terms. Here are some clearly understood analogies of a kilowatt hour of stored energy (not necessarily fully recoverable but stored). A water tank with 1,000 gallons of water on top of a structure or hill 315 feet above the reference point has the potential energy of 1 kilowatt hour. A 12 volt automobile battery with 83 amp hours of capacity has one kilowatt hour of stored energy. Now the kicker 3.1 fluid ounces (80 ccs) of diesel has one kilowatt hour of stored energy.

From the above analogies one can see that diesel has massive energy density per unit volume. Volume is the method by which things are stored in the three dimensional space that we live within. While many tout the high energy density of hydrogen per unit mass, the energy density per unit volume of liquid hydrogen is only one fifth that of diesel. Forgetting how expensive and inefficient it is to produce and store liquid hydrogen, it simply makes no sense to store a fuel that contains only 20% of energy content of another fuel when considering personal or other transportation vehicles. The space shuttle jettisons its external hydrogen tanks for this very reason. This space vehicle would be too large and too heavy if it did not have throw away hydrogen tanks. I doubt we can litter the roads with throw away hydrogen tanks for Hummers even if Arnie likes to say ?hasta la vista baby?..

Why does diesel have such a high energy density per unit volume? The simple answer is that the carbon hydrogen bond (hence hydrocarbon) when oxidized (burned) releases substantial energy. The second part of the answer is also that the specific gravity or density of diesel is much greater than that of liquid hydrogen. Diesel is more than 15 times denser than liquid hydrogen and more than 10,000 times denser than gaseous hydrogen. While the density of our politicians may not be tolerable, high density of fuels are a desirable quality.

Self service gasoline stations are now the norm in the US. There is hardly ever any mention in the news of accidents occurring while the least technical amongst us fill their vehicle tanks with gasoline or diesel. The amount of energy transferred into a 15 gallon tank from the diesel pump equals more than 600 kilowatt hours of stored energy. The transfer of the 15 gallons of fuel is accomplished in approximately 3 minutes. This implies a rate of energy transfer greater than 12,000 kilowatts or about the capacity of an electrical substation for a housing development with 8,000 homes. Another analogy is as follows: If the Hoover Dam?s entire electrical output is used to fill the kilowatt hours in the fuel tanks of personal vehicles, the Hoover Dam could simultaneously fill 165 vehicles. These vehicles would be filled with their energy in 3 minutes. Therefore 3,300 vehicles could be filled in an hour, or about 2,900,000 vehicles could be filled with their energy in a year. This is about half the number of vehicles in the San Francisco Bay Area. I guess we are not going to build two Hoover Dams soon in the Bay Area just to fill our cars with fuel only once a year.
Click to expand...
 
You must log in or register to reply here.

TRENDING THREADS

Back
Top