: Missing on dyno tests these days....

04-09-06, 12:27 AM
You know, more and more when I see dyno tests by these magazines, I don't see BSFC numbers anymore.

I am curious, is this something they have forgotten about? Measuing essentially the efficiency of the power output by the engine?

I remember reading an article on the SD455 going through jetting and timing paces on a dyno, and they would sometimes see slightly more power, but end up changing the jetting up or down, because the BSFC is too high.

Is this a lost art? In other words, dropping on that air foil on your TB on your LT1 might gain you 1 hp, but if it messes up BSFC, and makes it higher, it sounds like those mods should be avoided.

What I never did figure out is how that was determined. Anyone know? Can it be determined on EFI cars?

04-09-06, 10:08 PM

I don't think professional engine builders have forgotten the BSFC ratio or factor. Specific engine applications rely a lot on those numbers in relation to engine performance (HP), and fuel efficiency, which relates directly to engine temp., burn efficiency, and MPG.

A lot of engine build tests don't spend much time fooling with BSFC because they are usually interested in getting the highest HP figures in print.

At least that's my cynical opinion.

04-10-06, 12:45 PM
I never did figure out how BSFC is calculated, anyone know?

04-10-06, 01:03 PM
This should help you out:

04-11-06, 11:30 PM

Nice article, very concise...

BSFC = (observed fuel flow) / (observed brake horsepower)

I'm breaking out the books again with all this talk about E85.

Also, Nodih, thanks for the tuning info. sources.