^ butttt when you get into all that direct port piranha shot stuff... thats when you absolutly need to have better internals... i mean you really need to rebuild ur engine before you go with direct port... go with a wet zex kit... easiest and safest
Actually, that's only true if you jet the kit for high horsepower; Direct-port is safer since each cylinder gets it's share of N2O and fuel, wet fogger systems aren't as safe, because yoy can get fuel puddles in the Intake
manifold if you aren't careful; those puddles can detonate and mess up your Intake
This guy I knew with a cavalier and a 50-shot fogger system had this happen, a puddle ignited in the Intake
, and shattered the plastic manifold. it was funny as hell.
With direct port, you will not have that problem, so long as it's jetted correctly it will be safer, not more dangerous.
As for push buttons, I wouldn't rely soley on them. It would be best if you have redundant stages for nitrous triggering. Here's an example:
Have an arming switch, add a WOT (wide open throttle) microswitch to the TB linkage (Or on DBW cars, use a TPS sensor switch). Add a window switch or nitrous control module of some sort, then, lastly, add your pushbutton, all but the arming switch should be chained toghether into the trigger circuit.
Now, you flip the arming switch, if the pedal is floored, and the appropriate RPM is achieved, you press the button and the nitrous is triggered as long as you hold the button down. If you lift off the gas, rev too high, or too low, the nitrous will shut off, protecting the engine.
They also sell Fuel Pressure safety switches, if the adequate amount of fuel pressure is not present, the system will not engage. they're about $35 from Summit.
A nitrous system is only as smart as you design it to be.