The way the ZEX nitrous kit works:

ZEX kit I have is a dry nitrous kit, meaning it sprays from a nozzle, into your Intake, unlike wet kits, which spray into the fuel injectors. It has a little computer box on it, that is programmed to spray nitrous at WOT. You wire the box up to your Throttle Positioning Sensor, the sensor that tells your car how much gas to give it in conjunction with the amount of force your putting on the pedal. The voltage of the TPS goes up as you get on the gas. When the line reads like 4.2 or so volts, the nitrous solenoid 'clicks' and begins spraying, most cars TPS sensor at WOT are above 4.2 volts (4.4/4.6). When you let off the gas it stops spraying.

You have a switch inside that turns on the Nitrous Management unit, the little computer that comes with the kit, when you arm the nitrous, its ready to spray as soon as you floor it. When you shift gears, you have to let off the gas to shift (well unless you redneck power shift it with the gas to the floor), which cuts the nitrous, - if the nitrous kept spraying youd get alot of air, and no fuel, lean motor = Detonation which = BOOOOM.

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