Has anyone gone through the trouble of finding their actual BSFC on a dyno? I reviewed some logs and found mine to be around 0.78, which is quite high but not unreasonable...

 

I haven't...numbers not reliable enough What is your observed AFR?

 

AFR is not really important for BSFC directly, just flow rate and power produced. But I aim for around 0.8 lambda plus some meth on top.

 

What do you mean directly?

 

Because the AFR is not part of the equation. Just the amount of fuel being used is important. Obviously you can increase fuel usage changing the commanded afr, but BSFC is designed to be computed at a given operating condition (ie, constant AFR). What you would need to know is the power produced at a point, and the injector size and duty cycle at that same point. Changing AFR can change power, but usually not much if its close to ideal.

 

Well that was my point. If you're looking for actual BSFC, you'd need to be tuned at MBT. More than likely a tune at MBT that is leaned out enough to complement your timing value is leaner than what you're running...but it does make more power. And leaner would decrease fuel rate, etc etc.

 

I think I know what you mean...just your particular BSFC, not the minimum potential BSFC, right? Also, how do you accurately calculate the flow of methanol? A way to directly measure it would be useful...

 

More than likely you arent going to be on the ragged edge of AFR. Finding true MBT AFR and timing would take a very long time on the dyno...something most guys just dont do...so perhaps I should be more specific and say at whatever conditions you ran, which I am going to assume are reasonably close to MBT values, what was your BSFC? Correct, just your particular one, which im assuming is reasonably close to the minimum.

If anyone can provide: Horsepower, Injector size (at what pressure), and Injector duty cycle, BSFC is easy to calculate.

Fueling from meth would be tricker...you could convert the volumetric flow of the nozzles into a mass flow rather easily...but most controllers dont give a clear equation of the rate at which they increase pressure. Furthermore, most nozzles dont specify at what pressure they are rated...

I suppose you could figure it out if you have 4 data points, 2 at different rpms without meth, and 2 with meth. Wideband readings, injector size, boost pressure, and idc would be needed for each point. You would basically calculate the meth component as an extra flow on top of the normal injectors.

 

Hey I just assumed you camped out on the dyno for a day...wouldn't surprise me

 

Nah I just fiddeled with the dizzy and adjusted the carb jets twice and let it eat!