Quote:
Originally Posted by tyrannor
I assumed there would be only 1 bmep at each speed of the engine.
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1 specific point for each specific combination of engine operating conditions.
Engine speed is one condition , but not the only one.
Engine load is another condition.
If all other factors do not change and you know a specific engine's speed and the load it is under , than a BSFC chart can be an easy way to look up the operating efficiency under those conditions.
If however a specific engine can be changing other operating conditions at the same speed and load , the operating efficiency could still change.
For example, if at the same engine speed and engine load the engine can operate at different ignition timing ... that will effect the combustion characteristics ... or if under the same engine speed and load the engine can operate under different air to fuel ratios , that can also effect the combustion characteristics... with or without turbo active... etc... etc...
Quote:
Originally Posted by tyrannor
How would one achieve the lowest bsfc?
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If you want to design an engine to achieve the best BSFC that is allot of work , and years of study and design.
If you want to achieve the best BSFC for a specific engine , learn about the operating conditions for that engine ... A BSFC chart will show you for one set of conditions ... if the specific engine in question only has one BSFC that makes it much much easier ... if you want to try to improve the BSFC either better peaks or wider peaks , there are lots of modifications you can do to the engine.
Is there a specific engine you have in mind?
Quote:
Originally Posted by tyrannor
How would one operate with the lowest bsfc and also at a particular bmep?
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If the specific engine in question only has one BSFC chart than that chart will show you what engine speed ( RPM ) at that bmep ( load ) will result is the best BSFC.
Just remember it is the load the engine is under at that instant , not what you want it to be or think it should be.
If you make changes / mods to the engine to try and improve or change the BSFC chart ... you could get a new BSFC chart , but producing one usually involves time on a dyno.