thfonz98
1/2 ton status
You "may" see a drop in mileage due to cetane ratings in the US
Min. cetane rating in Germany is 51, US diesel stations are 40-51.
http://forums.tdiclub.com/showpost.php?p=1987974&postcount=1
Copy and paste from another forum post:
The cetane number measures the ignition quality of a diesel fuel. It is the % volume of cetane ( n-hexadecane, Cetane Number = 100 ) in alpha methyl naphthalene ( Cetane Number = 0 ), that provides the specified standard of 13 degrees ( crankshaft angle ) ignition delay at the identical compression ratio to that of the fuel sample. These days, heptamethyl nonane - with a Cetane Number of 15 - is used in place of alpha methyl naphthalene because it is a more stable reference compound. It is measured in special ASTM variable compression ratio test engine that is closely controlled with regard to temperatures ( coolant 100C, intake air 65.6C ), injection pressure ( 1500psi ), injection timing 13 degrees BTDC, and speed (900rpm ). The compression ratio is adjusted until combustion occurs at TDC ( the ignition delay is 13 degrees ). The test is then repeated with reference fuels with five cetane numbers difference, until two of them have comporession ratios that bracket tthe sample. The cetane number is then determined by interpolation, and the higher the Cetane Number, the shorter the delay between injection and ignition. Now, if the fuel is pure hydrocarbons ( does not contain cetane number improving agents like alkyl or amyl nitrates ) then the cetace number can be predicted fairly well using some physical properties, such as boiling point and aniline point. It's obvious from the above that the higher the cetane number ( 100 = normal alkane, 15 = iso-alkane ), then the lower the octane number ( 100 = iso-alkane, 0 = normal alkane ). This is because the desirable property of gasoline to prevent knock is the ability to resist autoignition, whereas for diesel, the desirable property is to autoignite. The octane number of normal alkanes decreases as carbon chain length increases, whereas the cetane number increases as the carbon chain length increases. Many other factors also affect the cetane number, and around 0.5 volume % of cetane number improvers will increase the cetane number by 10 units. Cetane number improvers can be alkyl nitrates, primary amyl nitrates, nitrites, or peroxides. In general, aromatics and alcohols have low cetane numbers ( that's whypeople using methanol in diesels convert it to dimethyl ether ).One of the obvious effects of running on low cetane number fuel is the increase in engine noise. Typically engines are designed to use fuels with Cetane Numbers of 40-55, because below 38 a more rapid increase in ignition delay. The significance of the cetane number increases with the speed of the engine, and large, low speed diesel engines often only specify viscosity, combustion and contaminant levels, as Cetane Number requirement of the engine is met by most distillate and residual fuels that have the appropriate propeties. High speed diesel engines ( as in cars and trucks ) virtually all are designed to accept fuels around 50 Cetane Numbers, with higher numbers being a waste. However, Cetane Number is only one important propety of diesel fuels, with three of the others being also very important. Firstly, the viscosity is important because many injection systems rely on the lubricity of the fuel for lubrication. Secondly, the cold weather properties are important, remember that normal alkanes are desirable, but the desirable diesel fraction alkanes
PS On the ten hour drive to Yuma, AZ from northern California I avg'd 57 MPG in my '03 Manual TDI Jetta. I was also loaded down with everything I needed down here for 5 months: clothes, tool box, computers, and one speeding ticket I acquired at the speed trap by Lost Hills on 46
Min. cetane rating in Germany is 51, US diesel stations are 40-51.
http://forums.tdiclub.com/showpost.php?p=1987974&postcount=1
Copy and paste from another forum post:
The cetane number measures the ignition quality of a diesel fuel. It is the % volume of cetane ( n-hexadecane, Cetane Number = 100 ) in alpha methyl naphthalene ( Cetane Number = 0 ), that provides the specified standard of 13 degrees ( crankshaft angle ) ignition delay at the identical compression ratio to that of the fuel sample. These days, heptamethyl nonane - with a Cetane Number of 15 - is used in place of alpha methyl naphthalene because it is a more stable reference compound. It is measured in special ASTM variable compression ratio test engine that is closely controlled with regard to temperatures ( coolant 100C, intake air 65.6C ), injection pressure ( 1500psi ), injection timing 13 degrees BTDC, and speed (900rpm ). The compression ratio is adjusted until combustion occurs at TDC ( the ignition delay is 13 degrees ). The test is then repeated with reference fuels with five cetane numbers difference, until two of them have comporession ratios that bracket tthe sample. The cetane number is then determined by interpolation, and the higher the Cetane Number, the shorter the delay between injection and ignition. Now, if the fuel is pure hydrocarbons ( does not contain cetane number improving agents like alkyl or amyl nitrates ) then the cetace number can be predicted fairly well using some physical properties, such as boiling point and aniline point. It's obvious from the above that the higher the cetane number ( 100 = normal alkane, 15 = iso-alkane ), then the lower the octane number ( 100 = iso-alkane, 0 = normal alkane ). This is because the desirable property of gasoline to prevent knock is the ability to resist autoignition, whereas for diesel, the desirable property is to autoignite. The octane number of normal alkanes decreases as carbon chain length increases, whereas the cetane number increases as the carbon chain length increases. Many other factors also affect the cetane number, and around 0.5 volume % of cetane number improvers will increase the cetane number by 10 units. Cetane number improvers can be alkyl nitrates, primary amyl nitrates, nitrites, or peroxides. In general, aromatics and alcohols have low cetane numbers ( that's whypeople using methanol in diesels convert it to dimethyl ether ).One of the obvious effects of running on low cetane number fuel is the increase in engine noise. Typically engines are designed to use fuels with Cetane Numbers of 40-55, because below 38 a more rapid increase in ignition delay. The significance of the cetane number increases with the speed of the engine, and large, low speed diesel engines often only specify viscosity, combustion and contaminant levels, as Cetane Number requirement of the engine is met by most distillate and residual fuels that have the appropriate propeties. High speed diesel engines ( as in cars and trucks ) virtually all are designed to accept fuels around 50 Cetane Numbers, with higher numbers being a waste. However, Cetane Number is only one important propety of diesel fuels, with three of the others being also very important. Firstly, the viscosity is important because many injection systems rely on the lubricity of the fuel for lubrication. Secondly, the cold weather properties are important, remember that normal alkanes are desirable, but the desirable diesel fraction alkanes
PS On the ten hour drive to Yuma, AZ from northern California I avg'd 57 MPG in my '03 Manual TDI Jetta. I was also loaded down with everything I needed down here for 5 months: clothes, tool box, computers, and one speeding ticket I acquired at the speed trap by Lost Hills on 46
This thing has a cat and 2 mufflers that I'm gonna be getting rid of and building a 2.5" system for in the hopes of getting it in the 40s for all stop and go city driving.
