Jean Fouche wrote:

     Dear Paul

     What does BSFC stand for? Is it an emmision standard?

     Jean Fouche
     Learning South African

BSFC stands for Brake Specific Fuel Consumption. It is a very old term
and is measured in weight of fuel burned for each HP generated in one
hour. Lets say we have a 100 HP engine and it is burning  five gallons
an hour. What is the BSFC. Gasoline weighs about six pounds per gallon
so the number of pounds burned is thirty pounds. 30/100 = .3 BSFC.
A very low number for a gasoline burning engine. Rather unlikely.

BSFC can be used in reverse. Usually these types of engines burn
around .45 BSFC. Thirty pounds of fuel in one hour at .45 BSFC
would be 30/0.45 or sixty six HP. If your friend is telling you
his engine is generating 200 HP and burns 10 gallons an hour
don't believe it. It is generating about 133 HP.


Here are some typical numbers.

0.4 to 0.5 for almost all gasoline burning four stroke engines.
The wankel type rotary is near the top at about .47 to .50.
Or the bottom depending on how you look at it.

Diesel engines are in the range 0.3 to 0.4. But diesel fuel
is heavier than gasoline.

0.6 to 0.65 for almost all two stroke gasoline burning engines.
There have been some improvements lately with direct injection.

0.65 to 0.7 for gas turbines with shaft outputs. Turbo props. PT6

There are a couple of other rare categories.
Below 0.3 for a gasoline burning four stroke turbo compound
aircraft engine. Long story see the web site.

Below 0.2 for a combined cycle engine. Exhaust heat is converted 
to steam. The steam is used in a steam turbine to recover some
of the 50% waste heat energy found in the exhaust of almost all 
combustion engines.  

BSFC can also be given in metric units. In that case it is
grams per HP hour.

How did I do guys? Anybody want to add to this?

Paul Lamar
 
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