Nothing is 'safe' But 150 is the max that is recommended on a stock motor. Just jet it rich and you should be okay. BTW, nitrous loves exhaust, so do the basic intake/exhaust mods like CAI, muffler, headers.
At what RPM should you spray nitrous?
2500rpmA: We recommend at least 2500rpm as a minimum for nitrous system activation. This ensures that you will not have excessive cylinder pressures that could cause engine damage. The use of an RPM window switch ensures no premature activation.
How much HP do you get from spraying nos?
Well, you're in luck because adding nitrous is just as cheap and effective. Plates such as this LS-style example from NOS can deliver from 75 to 250hp to the wheels of your modern engine-equipped ride.
How much HP does a 100 shot of nitrous add?
100 flywheel horsepowerMaxwell: A “shot” is typically how much horsepower the nitrous system is adding to the engine. For instance, a “hundred shot” is adding 100 flywheel horsepower on top of what the engine makes normally. The horsepower level of the nitrous kit can is easily changed by swapping out metering jets.
Does nitrous ruin your engine?
Does nitrous damage your engine? No. Using high-quality nitrous that's been fitted correctly and according to the requirements of your car should be safe for the engine and will not cause the engine to overheat or explode.