Nitrous Oxide System

Nitrous oxide systems come in a lot of different types and styles, but they generally fall into one of two categories. "Dry" systems inject only nitrous oxide into the engine, and usually rely on the ECU of a fuel injected car to deliver additional fueling. These are usually smaller systems that deliver a net horsepower gain of 50HP or less. They are less expensive and somewhat easier to install compared with the other category, "wet" systems.

Wet systems incorporate both a nitrous oxide and fuel delivery solenoid, and use a special nozzle designed in such a way that the spraying nitrous atomizes and mixes with the fuel. These systems are most common in larger or more potent nitrous installations.


Below is pictured my custom fabricated NX wet system. Note the fuel (red) and nitrous (blue) solenoids and thier corresponding distribution blocks. This setup uses a total of three nozzles feeding into a spacer plate just below the progressive carb. This optimizes the flow of nitrous at wide open throttle when both the primary and secondary of the carb are open. The choke, and anything else that could be removed, were stripped off to make room for the nitrous plumbing.


The primary enemy of an engine under nitrous is lean detonation. Lean detonation occurs if fuel pressure drops, or a fuel solenoid fails, or fuel line or nozzle freezes up. On more potent systems, lean detonation with nitrous can remove the head of a motor or send a connecting rod happily through the engine block or oil pan. For this reason, adequate flow and pressure of fuel is of paramount importance. Frequently this may entail additional items like dedicated fuel pumps or regulators. Always err on the side of too much fuel, it is much safer for the engine to run rich on a nitrous burn than to lean out. Fine tuning the mixture is usually done by an examination of spark plug condition after a nitrous burn. Plugs should go from the regular "chocolate" color to a light beige or near whitish color, but they should not be scaled, melted, or burned.

The major players in the nitrous game as of the time of this writing are NOS (Nitrous Oxide Systems), NX (Nitrous Express), Venom, and ZEX. Both NOS and NX have been around a long time, and have a proven history of reliability. Venom and ZEX are newer entries, but hold the promise of a technology called "pulsed solenoids". This allows the solenoids to be modulated for a gradual increase in power, to reduce stresses on the engine. this technology is an offshoot of an aftermarket product originally market by ignition supplier Jacobs Electronics, the "Jacobs Nitrous Mastermind". Since this really doesn't have a whole lot to do with the basic setup and can be added later, I opted for the Nitrous Express system. The "Pirahna" fogger nozzles looked like those best suited to my application, and the carb geometry I needed to work around.


The installed solenoid plate.

Wiring the system is fairly straightforward. An arming switch provides power to a wide open throttle switch mounted on the carb body. When the system is armed, and the throttle is opened up completely, nitrous and fuel solenoids are simultaneously energized. Ground to the solenoids is broken by a fuel pressure safety switch in most applications, although other devices such as the RPM output of an ignition controller may be incorporated as well.


In my setup, I added a few custom touches. The arming switch is covered by an aircraft safety toggle. there is an arming pilot and also a purge button and purge indicator pilot lamp. I also added a key switch in series with the arming switch and purge. This is designed to keep an overly curious parking attendant or unauthorized person from causing any mishap.



View of bottle looking toward back of car.


Aluminum structure atop engine secures purge tube.