wanting to know were i should put my AFR's for 150-200 shot? is there some sort of equation? on my "Tuning School" book it says forced induction should be 10.5:1-12.0:1 does this apply for nitrous?

 

With blowers/forced induction you add fuel for inlet charge cooling to increase the detonation threshold on pump gas. Nitrous is a different ball game, but the same rule applies, for a different reason.
Nitrous has a stoichiometric A/F ratio of about 7:1, so you need to calculate the desired AFR on the spray, based on your optimum N/A AFR and HP output on and off the spray. If your N/A AFR is 12.6 and HP is 400, with a 150 shot on that engine you would want an Nitrous AFR of about 11.1. That's what I've come up with for my truck for when I go up to a 150 shot. Right now it runs in the mid 10's on the spray w/ the 125 shot, because I can't get the N/A AFR to do what I command (it's running 12.0 instead of 12.8), but that's a story for a different thread.
There is a calculator in Greg Banish's "Engine Management Advanced Tuning" book (if thats what you're reading) on page 101. For a 300 HP motor with an N/A AFR of 12.7, with a 100 shot you would look for an AFR of about 11.3 on the spray.
All in all, for most motors, low to mid 11 AFRs is what you should be seeing, especially if you're running pump gas. Anything higher and you're asking for burnt pistons and broken ring lands. Take it from a graduate of the school of many hard knocks...

 

There is no set A/F for nitrous. The only accurate way is to read the plugs. My truck ran in the low 12 range, thats what made the plugs happy. If it were me, I would would start in the mid 11's and keep timing low, and adjust from there. Running mid 10's is asking for trouble.

 

What kind of trouble? Bore wash, carbon build up, plugs fouling? Most of the application specific nitrous kits come with jetting on the rich side, and all of them that I've seen AFR readings taken from have readings in the 11's, and mostly, the plugs come out of the engine looking as clean as new after a run. If you have the timing/octane and plug heat range right, I'm sure you can make more power with a low 12 AFR, but there probably won't be any room for error (high bottle press, lower octane, fuel press drop, etc.).
I agree plugs are the best indicator for tuning any engine. Problem is, they're a lot harder to read than an AFR gauge for most folks.

 

12-13...10s and 11s is askin for trouble like built408 said

 

I had a pretty good write up from monty smith.. its all in the timing and plugs as built 408 said. monty has cars sprayin a 900 shot runnin 13:1 afr. when i ran a dyno I seen alot of people lose hp tryin to get them in the low 11 vrs mid 12s.

 

put it this way when i had mid to high 11's afr and 24 degrees of timing on 100 shot mine would pretty much hook from a 25 30 roll now that my afr is 12.4 and 22 degrees of timing, i could add more if i wanted too,its a smoke show from a roll.