Nitrous Tuning

The amount that's safe depends on what it makes NA, the machining, the fasteners, the parts, and the tune. Assuming stock rods and crank and the typical 450hp NA - I'd limit it to 300. A good progressive controller could raise that a bit. The old school retard is 2° for every 100hp or for extra safety go 3°/100hp. As the system gets bigger the plugs are more important, as are the fuel and bottle pressures. 400-500 is a big hit in one shot on small tires or stock suspension.