Car weighs about 3000 plus me, so figure 3200 race weight.

Makes about 500 rwhp, shift points at 7k. 3 speed auto trans. Tires are 28 inch tall.

I need a gear for NA runs, and another for 300 shot fogger runs. I was thinking 4.11 and 3.50 respectively, but I haven't been able to find a good formula.

Anyone help on this one?

 

The question is how quick do you want to go? With that light of a car you won't be giving up very much ET if you choose something in the middle and you could just change tires for N/A and n2o. Like putting a 3.50 gear in the car and run 26" tires for N/A so it would be like having a 3.73 with 28' tires, then just run a 29" tire for n2o which will give you better traction. The cars running cheap street run 9.90's-10.30's with n2o on 26" tires with 3.70 gears for example. I am running 3.42's and 26x11.5 ET streets and my 3550lb car runs 11.6's spinning with a 355" engine so my engine would run 10.9's tto 11.00's in your car with 3.42's. N2o works really well with a higher gear b/c it loads up the engine and pulls like a freight train. So you really can't go wrong with a high gear on n2o. You won't go wrong with anything from 3.50 to 3.90's and just change tires if it's crossing to high. Later Clint