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Originally Posted by vex
Fix some of your issues with your math
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The math is correct as far as I can tell. I used an intermediate density of 0.72g/mL because gasoline covers a broad range of densities. Perhaps you don't like that I used engineering units. (I really didn't want to put 0.0001656 L/rev).
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Originally Posted by ReTed
You might be right about a steady state snap shot of the engine, but when most people describe "BSFC" for a particular engine, we're talking about the average BSFC for all ranges.
I've heard 0.60 - 0.65 used in most applications when talking about a 13B.
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Actually BSFC is typically expressed as a chart with engine load on one axis, speed on the other axis and BSFC indicated by islands (similar to a compressor isentropic efficiency map for a turbo).
Many engines are rated at peak BSFC which is commonly computed at the highest BMEP (highest torque output). This is the point that I picked.
I will develop a full load BMEP curve for my engine at a variety of speeds, but not tonight. I don't have partial load data.
I agree that you have heard those numbers, so have I, but I also heard that I should never exceed 26 degrees of ignition advance and to always run rich of 12:1 AFR. If you do that, you will have a BSFC of 0.6 lb/HPh