I've put a hand on a zex dry nitrous kit for cheap. This kit is initially for 5.0 mustang. It looks like it works like the NOS kit #5115. Is it safe to run a 75 dry shot on my stock 89 TPI???

The only mods I have are custom air intake, hedman headers 1 5/8, 3in catback with dynomax ultra flow. Stock fuel pump and #22 injectors.

 

For running a dry kit, you look at injector duty cycles...


Injector flow rate (lb/hr) / brake specific fuel consumption (lb/hr/HP) * number of cylinders = HP at 100% injector duty

The brake specific fuel consumption (BSFC) is about 0.5 for normally aspirated engines, 0.55 for supercharged, and 0.6 for turbocharged. I use .5 for nitrous engines...


22 / .5 * 8 = 352hp @ 100% duty cycle

Most stock injectors prefer a 80% duty cycle to remain happy. So, 281.6 HP is what your injectors could supply..

Subtract the HP you're making now from the 281.6, and that's the dry shot you can run 100% safely.

I've seen injectors get stretched as far as a 98% duty cycle, but do it at your own risk


(ALL HP FIGURES ARE CRANK HP, NOT RWHP)

 

my experience,
a 75 shot seems to be ok but the 100-125 makes them detonate and break stuff after a while unless injectors are swapped and fuel pumps are installed too.