Interesting Diesel facts from the BMW motorcycle website

[desertryder]

To read the entire post go here



http://bmwsporttouring.com/ubbthrea...463688&page=1&view=collapsed&sb=5&o=7&fpart=1



Really interesting article in the WSJ today about converting natural gas to diesel. There's a $20+ billion dollar operation being built in Qatar right now, located there probably because they sit on 17% of the world's NG capacity.



The diesel they are creating is about 1/3 the cost of oil (per barrel, at the current high prices), and get this: it has no sulfer (thus burns cleanly) and can be used in current diesel engines without modification. Apparently it's being used in South Africa and somewhere else right now, though not on a wide scale.



Also in the article was a quantification (that's a stupid word) of diesel usage. Less than 1% of passenger vehicles in the US are diesel. It's more than 50% in Europe. We're talking new vehicles sold.



I'm guessing fuel economy is the primary driver of this trend, where their gas prices are high? But that leads to a few questions for the collective:



1) Why is diesel a more efficient fuel? Is it because of the higher allowable compression, and thus more "bang" for that buck?



2) Why do diesel engines last longer? Is it because of how the engine must be "overbuilt" to handle that higher compression?

 

[mberry]

1. No. There is more energy in a gallon of diesel than a gallon of gas.



2. Yes. They must be built strong not only for the compression but heat as well.

 

[Froadin]

diesel has a higher BTU per pound then gasoline. So it has more energy per unit of measure. The compression is needed to generate enough heat to light the fuel.



Diesels are built tougher, but they also only rev about half the RPM (typically). They are also more thermally efficient. This means that more of the energy from the fuel goes into pushing the piston, and less into just heating parts of the motor up. Gasoline motors are less efficient, waste more power, and put more heat into the engine rather then useable power.



Others will respond with much better answers then this though

 

[Hohn]

diesel has a higher BTU per pound then gasoline. So it has more energy per unit of measure. The compression is needed to generate enough heat to light the fuel.

Actually, per POUND-- gas has more energy in BTUs.





By the GALLON, diesel has more energy. Diesel weighs more per gallon.



Do the math for BTUs per gallon and lb/gallon and you will see this is true.



jlh

 

[Forrest Nearing]

diesels also last longer because fuel isn't drawn in on the intake stroke... and it's an oily fuel on top of that.



Forrest

 

[Froadin]

Actually, here are the BTU's for the fuels.



One source.

Diesel fuel 128,000 and 130,000 per gallon.

Gasoline 109,000 to 125,000 Btu per gallon.



Another.

124,000 Btu per gallon of gasoline

138,000 Btu per gallon of diesel



Another.

Diesel fuel 128,450 per gallon.

Gasoline 116, 090 per gallon.



Doesn't seem to be exact, but they all show more BTU per gallon with diesel.

 

[Vaughn MacKenzie]

It would be interesting to know efficiency based on BTU. How much usable work can you get out of a gasoline engine burning 100,000 BTUs worth of gasoline compared to a diesel burning 100,000 BTUs of diesel? Most of us would agree the diesel would win here, because of direct cylinder injection, lack of restrictive throttle plate, and ability to run super lean fuel ratios (not dependent on it like a gasser) when running lighter loads.



Vaughn