Injector size/Dry nitrous



I need to know what size injector to run in my new setup.
I have dne a search on the web and used many of the online calculators with many differnt results.

I will be using a fast sequential setup with a tnt dry fogger(small block chevy).We are shooting for 680 h.p. on the moter with a 500-600 horse shot.This is a drag car that will see the street maybe once a month.

Any input would be great.What b.s.f.c should I use when figuring for the nitrous .What duty cycle.

Any input would be great.
Thanks ED
I would get a set of 83s. If you figure a 0.5 BSFC (which I think should be close but I am no nitrous expert) 83s should support around 1300 hp at max duty cycle and 45 psi fuel pressure.

With that much nitrous on a small block you may be at the point where your O2 is not much of a tuning tool anymore. From what we have seen, when you get to the point where the horsepower level of nitrous is the same or greater than the displacement of your engine (400 hp shot on a 400 CID engine, for example) the O2 sensor doesn't know what to do anymore. This point seems to be where you are shoving enough unused nitrous right out the exhaust that the airflow signal across the O2 sensor isn't really representative of what's happening inside the motor anymore. You would be best off to know exactly what BSFC level you want to run at and pay close attention to the volume of fuel in lbs/hr you are injecting on nitrous. Look at your spark plugs to see how you are doing. No data acquisition tool in the world will ever be a better indicator of what your engine is doing than reading the plugs.