BSFC and Air/Fuel Ratio

turboman1

turboman1

New member
Joined
Aug 20, 2008
Messages
248
Couple of quick questions

1) What is the aprroximate BSFC (lb/(hp*hr)) of around a 750-800 hp 12 valve cummins.

2) At what air/fuel ratio does one start to see visible black smoke?

Thanks
Adam M.
 
I believe the smoke free A/F ratio is around 20-22:1.
Don't know for sure, but I read that somewhere.
 
turboman1 said:
Why at 16:1 is not the extra fuel just being wasted out the pipe or does it actually burn some to create a better combustion?

Adam
Click to expand...

Depends on how you look at it. A diesel is not a an air throtttled engine. Well some of the new ones are. But that is another story. Basicly if you can burn every once of 02 you will make more power. So if you have air mass "X" in your cylinder and an AFR of 16:1 you will make more power than you will at 20+:1 with the same air mass "X". That is fact. To make power you need to burn as much of the 02 as you can. That means smoke. Unless you have huge twins or lots of :nos::nos::nos:. Those are both good options for cleaning up smoke at the drag strip. But if your in a limited turbo class like pulling you need to make as much power as you can with the limited air mass you have. Again that means smoke.

Yes I have dynoed and measured my AFR with a wide band.
 
Johnboy,

do you have the dyno sheet that showed the A/F ratios for corresponding rpms?

Thanks
Adam M.
 
turboman1 said:
Johnboy,

do you have the dyno sheet that showed the A/F ratios for corresponding rpms?

Thanks
Adam M.
Click to expand...


What I have is a large handful dyno sheets where I was logging the A/R with my Innovate hand held as I was working on my timing and fueling. In my setup the difference was large between 16:1 and 20:1. The more air you move the bigger the difference should be.
 
You mean the A/F ratio fluctuated between 16:1 and 20:1? If so what was the performance gain between going from 20:1 to 16:1?

Thanks
Adam M.
 
You must log in or register to reply here.
Back
Top