EFI Tuning Fundamentals: BSFC Values

I'm curious to know how the typical BSFC values for different engines which was mentioned in the tutorial calculated?

Here is a good page with the details on BSFC calculation.

https://x-engineer.org/automotive-engineering/internal-combustion-engines/performance/brake-specific-fuel-consumption-bsfc/

Thanks David for the helpful info. Cheers

Jolly good article, David.

To summarise, Omair, it's the fuel used to produce the power, in American it's "pounds of fuel per horsepower per hour".

Way back in the day, 0.5 lbs/hp/hr was about average at peak power, but some modern engines can be as low as 0.4 lbs/hp/hr with some being even more fuel efficient. The actual number will vary with rpm, load and the relative efficiency of the engine under those conditions - that's why you can see the map variations.

While most of the time, tuners are aiming to get the most torque/power out of the engine, there are times when a small amount of torque/power may be sacrificed for better BSFC numbers - economy if you prefer. You have probably seen mention, in motorsport, of drivers selecting different maps, or engine modes - this will usually be a graduated set of pre-set maps giving better fuel economy to eke out another lap, or two, between fuel stops while sacrificing a little lap time.

In aviation, you may have heard the term "lean best" or "cruise power" - this is basically the same thing, the fueling is leaned out to give the most torque/power for the amount of fuel used. Production road vehicles do the same thing by careful fuel calibration, as they generally have to balance acceptable engine power with good fuel consumption, while still meeting emission standards.