Nitrous Oxide Systems For Your 4x4 Truck - A Nitrous Oxide Primer

When Nitrous Works
There are two terms that are important to understand about using nitrous oxide: armed and activated. A nitrous system is armed when the system is turned on and the valve from the bottle is open. There's no injection going on at this point, but the system is ready. Nitrous injection is activated by a switch or trigger that opens the solenoid to release the nitrous and, at the same time, introduce supplemental fuel to the intake charge.

Since they're intended for drag-race-style, high-speed bursts of power, most nitrous systems are designed to activate at wide-open throttle (WOT). Activation is not always done via the steering-wheel-mounted button that the "Fast and Furious" boys made so famous. It certainly can be, but some systems activate automatically. The EFI-engine kits from Nitrous Oxide Systems (NOS), for example, have what's called a WOT box with a wire lead that's connected to the throttle-position sensor. When the lead reads voltage that indicates the throttle is wide open, it activates the nitrous solenoid.

Here's how the dry system looks under the hood of a 2000 Durango. Pretty stealthy, eh? The only obvious tip-offs to the system's existence are the braided hose leading into the airbox and the solenoids, which in this photo are barely visible.

Here's how the dry system looks under the hood of a 2000 Durango. Pretty stealthy, eh? The

And here is where we get to the heart of the question, "Does a four wheeler need nitrous?" How often do you find yourself at WOT when you're four-wheeling? Probably never, unless you spend a lot of time dune-bashing or mud-bogging. So are you out of luck as far as nitrous goes? Not necessarily. Some companies make controllers that feed nitrous progressively into the intake system, taking nitrous injection out of the all-or-nothing realm of WOT use and adapting it for folks who may want an occasional pick-me-up, like when climbing a rutted hill, blowing over a dune, or pulling a trailer up a long grade.

There are a couple of types of partial-throttle controllers on the market. The one that's most 4x4-friendly is the throttle-position-controlled unit from NOS. Unlike a time-based controller (which is better suited to drag-race applications), the throttle-position controller feeds nitrous into the system gradually as you roll into the throttle.

One word of warning about the progressive controllers, though: They may not be 50-state emissions legal. That's because the California Air Resources Board (CARB), which often drives issues of legality with its testing and certification processes, granted its exemption for nitrous kits based on the fact that the nitrous would only be used under WOT conditions, and that most street-driven cars see very little time at WOT. So, sorry Californians. Unless you want to disregard the law, you're back to nitrous as a WOT tool, only.

Tuning For Nitrous
The good news is, if you're adding a relatively mild amount of nitrous to a bone-stock engine, there's little tuning to be done. Nitrous shots that produce around 100 hp won't overly tax your V-8's reliability. Just make sure the engine is in a good state of tune and that you're using premium gasoline. If you have a fuel-injected engine, it's a good idea to clean and match the flow of the injectors, since they will have to work harder (pumping anywhere from 30 to 40 percent more fuel) when the nitrous is activated.

That small switch on the left (below the temp control dial) arms the nitrous system in Golightly's Durango. The little red button above it is used to purge the lines. Golightly doesn't use a button to activate the nitrous; the system does that automatically when it reads voltage on the throttle-position sensor indicating that the pedal is to the metal.

That small switch on the left (below the temp control dial) arms the nitrous system in Gol

Some nitrous system makers recommend changing spark plugs for nitrous use, either to a plug with a short ground strap or one in a cooler heat range. We're not going to take sides in the debate-go with the advice given to you by your nitrous supplier of choice.

One area the nitrous companies agree on is this: Be conservative when adding nitrous to your engine. Make sure you've got plenty of extra fuel running to the system, and start out with small nitrous jets and work up to the bigger shots when you're ready. That'll save you from making mistakes that may result in severe engine damage.

The experts told us engine modifications for nitrous use are only necessary if you go really aggressive-150- to 200hp nitrous shots, for example-as the cylinder pressure and energy generated with that much power production will stress the pistons, rods and head gaskets.

In a 4x4, however, even modest nitrous use may require modifications behind the engine. On the street, if you put too much power to the wheels, chances are good you'll just overwhelm the tires and blow the extra power off in a cloud of tire smoke. On the trail, though, grippy tires may not spin as easily. So the weakest link may be somewhere else, like the axles, U-joints or transfer case. Unless you've got a really bulletproof driveline, take extra care the first few times you use the nitrous off-road.

This is just a starting point if you're interested in adding nitrous to your 4x4. There's a ton more information out there on everything from nitrous bottle warmers to fully custom nitrous setups. Check out the nitrous system manufacturers listed here for more information about your particular setup.