93transam1234

I dont have a dyno but my mods in my sig.

Trying to find out if i have enuf injector for my setup
(stock Inj.)

Jameslt1TA

You probably do. But the best way is to get datamaster and run a wot log on your car. See what the % duty cycle is. I think that anything over 90% is pushing it.

93transam1234

i got auto tap, i am just trying to understand how the calculation is done

Jameslt1TA

It should tell you the injector duty cycle. Im not to sure about auto tap though. I would say that you have enough injector for you setup but it would be nice to know.

93transam1234

it doesnt show mr duty cycle, it shows pulse with and inorder to calculate duty cycle i need to know the BSFC

1racerdude

BSFC will only be learned on an engine dyno.
There are recommended figures to calculate the injector size. A N/A engine is usually rated at .5,but .45 is relevant too if it's efficient.Just use .5 and ya will have a small amount of growing room for more HP.

Injuneer

You don't need BSFC to calculate duty cycle. To calculate duty cycle you need the pulse width and the RPM from a frame of data. Divide the pulse width by the number of milliseconds it takes to complete 2 crank revolutions at the RPM in the frame. That's duty cycle.

Time for two crank revs in milliseconds = (2/RPM) X 60,000

At 6,000rpm, time available is 20mSec. An 18mSec pulse width would give you:

18 / 20 = 0.90 = 90% duty cycle.

You do need BSFC to calculate required injector flow in #/HR. As indicated in the post above, you get that number with the engine on an engine dyno, measuring both flywheel HP and mass fuel consumption, see typical dyno output sheet, with BSFC in 5th column from right. That's for my engine with a 250 shot of nitrous, so the BSFC peaks at 0.53 #/HR/HP. Running NA, its about 0.44

http://members.aol.com/Fredrick518/dynoN2O.jpg