Subscribe to a magazine

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

4x4 Jeep Cherokee
Drew Hardin
| Contributor
Posted September 1, 2002
Photographers: Manufacturers, Michael Rudd

Does a 4x4 Need Nitrous?

Did you see "The Fast and the Furious" last summer? It was a really silly movie about drag racing rice rockets, but it made stars out of an actor called Vin Diesel and a gas called nitrous oxide. Vin we can take or leave, but nitrous is far more fascinating stuff. It's "throttle in a bottle," a means to literally bolt on horsepower. Sounds good if you're trying to fly down the quarter-mile, but does nitrous have a place in a four-wheeler's world?

The answer to that depends on how you use your 4x4 and where you think it needs improvement. Nitrous is what's called a power adder. If you want your V-6 to feel like a V-8, or your small-block to feel like a big-block, bolting on a nitrous kit may be one of the easiest ways to get there. Unlike other power upgrades, like a turbo or supercharger, nitrous-oxide injection only works when you want it to. When the system is turned off, your engine operates as if the gas wasn't there. So to anyone else driving your truck - your mom, your wife, your dumb boyfriend-it feels like it's still stock. Once you've armed the system and mashed the throttle, though, it's magic time.

So, just how much power are we talking about? As a general rule of thumb, if you're leaving your engine otherwise stock, you can add up to 140 hp to a small-block V-8, 75-100 hp to a V-6, and 125-200 hp to a big-block V-8. If you're willing to make a few additional engine modifications, the power numbers can go much higher.

What'll this cost you? After a quick check of a couple of performance retailers, we found nitrous kits for small-block V-8s in GM pickups for between $560 and $660. Some of those systems were even 50-state legal.

Want to know more? We thought you'd never ask.

This illustration shows how a wet system is plumbed between the carburetor and intake manifold. The cylindrical objects labeled 8 and 9 are solenoids; 8 controls the flow of nitrous, 9 the supplemental fuel.

How Nitrous Works
Probably the biggest misconception about nitrous is that it's some sort of super racing fuel. It's not. Nitrous oxide is an oxygen-carrying substance (with the chemical formula N2O) that is in a liquid state when it's stored in a bottle. Injecting nitrous into an engine turns the liquid into a gas, and the temperature of combustion releases the oxygen molecules so they're available to the combustion process.

In a way, nitrous oxide is like a chemical supercharger or turbocharger. It introduces more oxygen into the engine so it can burn greater amounts of fuel to increase horsepower production. Also, because the nitrous is so cold when it enters the engine, it lowers the temperature of the whole intake charge in the manifold by as much as 65 degrees F, making the air/fuel mix denser. A denser mix means more air and fuel can pack into the combustion chamber, which also boosts power

But nitrous oxide does require supplemental fuel to make power. If you don't put more fuel into a nitrous-injected engine, all that extra oxygen will just burn the existing fuel faster, resulting in pre-ignition and damaged pistons. For this reason, nitrous-oxide kits include some means of pumping additional fuel into the engine.

There are three basic forms of nitrous delivery: wet, dry, and direct-port. Only the first two really apply to trucks, as the direct-port method (where nitrous and fuel are delivered directly into each intake port) is found mostly in racing applications.

Wet delivery, used with a carburetor or throttle-body injection, is called that because the nitrous is introduced at the same point as the fuel, and the two move together as a plume of atomized fuel and nitrous vapor through the manifold and into the cylinders. Typically, the nitrous and supplemental fuel are sprayed from a plate mounted either directly below the carb or, in a TBI application, a few inches ahead of the throttle body.

So-called dry nitrous delivery is used in port-injected engines, where the intake manifold is designed to flow air only. The nitrous is sprayed into the air intake, and the supplemental fuel comes from the fuel injectors at the ports. To get the extra fuel from the injectors, electronics in the nitrous system fool the engine's ECU into thinking the motor is cold and is receiving cold air. (This is why the temp gauge on the dash will fall to stone cold when the nitrous activates.) Under those conditions, the computer tells the injectors to spray fuel for a longer period of time. The computer also dials back any advance in the ignition timing, which is a good thing. Since nitrous oxide accelerates the burn rate of the fuel, you don't want the ignition system doing anything to start the burn sooner.


View Photo Gallery

Don't Call It "Noss"
One more thought about nitrous and "The Fast and the Furious": The street racers in that movie called nitrous oxide injection "noss," after the letters "NOS" stamped on the nitrous bottles. Don't do that. It'll make you look stupid. "NOS" is an acronym for the Nitrous Oxide Systems brand. It's a word like "Kleenex" on the side of a tissue box. Some bright pennies in the import racing community do actually call it "noss," and the movie was imitating that lingo. But they're just wrong. If you want a nickname for nitrous oxide, try "squeeze," "spray," "juice," "laughing gas," "the bottle," or some other term that real racers use.


Nitrous Express
Wichita Falls, TX 76310
Nitrous Oxide Systems (NOS)
Costa Mesa, CA 92626
So-Cal Speed Shop (NOS West Coast facility)
Pomona, CA 91766
Load More Read Full Article