Nitrous oxide. Even the name sounds cool. And while Hollywood movies glamorize it and make it seem like some out-of-this-world mystery gas, you should know nitrous is not that fancy. In actuality, the magic is nothing more than a mix of two of Earth's most common elements: nitrogen and oxygen.
Engines rely on a mixture of oxygen and a fuel (such as gasoline) ignited by a spark to make combustion and power. And nitrous simply provides your engine with copious amounts of oxygen. The result greatly enhances the combustion process, and massive gains in horsepower can result.
The big-bang-for-the-buck comes from the fact that nitrous kits are relatively inexpensive, simple in design, easy to install, and pack the potential to drastically increase the horsepower output of your engine with the push of a button. Additionally, nitrous systems can be turned on or off, making them perfect for street/strip applications. Some nitrous installs can see a pickup of 80-150 hp, sometimes with an even greater improvement in torque. A full second or more can be lopped off quarter-mile times, and it can be done without sacrificing drivability. But nitrous has its own evils, and we're sure you've heard the horror stories.
What we've learned is many of the mishaps come from nitrous misuse. More often than not, the biggest problem with nitrous comes from users who lack an understanding of the product and those who get greedy and go after the biggest shot they can find. In actuality, this is the same as the guy who buys a supercharger and tries to run 16 pounds of boost on 89-octane fuel or without the proper tune-up.
This article will expose some common mistakes and offer some tuning tips to help you get the best performance from your nitrous system.
ENGINE BASICS
Before we can bolt up a bottle and extract extra power, it's important to understand how your engine produces that power. Simply grasping this theory will help you understand why adding nitrous increases the output.
Stated in basic terms, the internal combustion engine is a mechanical device designed to harness and apply the power produced from the combustion of fuel and oxygen. Alone, an engine cannot make power, but with the proper ratio of fuel (gasoline or other), oxygen, and spark, the internal combustion engine can generate torque and horsepower. Some of the smallest engines make as little as a 1/2 hp, while Top Fuel engines that burn nitro-methane can make upward of 8,000 hp.
Engines work by ingesting the mixture air through the induction system. The air is mixed with a fuel by a carburetor or fuel injection system and fed to the cylinders. Pistons then compress the mixture of air and gas into the combustion chamber. At a predetermined point during the crankshaft rotation (usually just before the pistons reach TDC) the air/fuel mixture is ignited by a spark plug. If the engine is tuned properly the mixture burns rapidly and energy is released in the form of heat.
It's important to note that the mixture does not explode, but rather it burns rapidly. As the mixture burns the gasses expand, the pressure in the cylinder rises, and force is applied to the pistons (and rods). Thus, it is simply the cylinder pressure that forces the pistons down to rotate the crankshaft. The crankshaft, in turn, transfers the energy from combustion into a rotating force (and we call this rotating force torque). You can see that more cylinder pressure equals more power at the crank.
One way to raise cylinder pressure is to burn more fuel, because burning more fuel should create more heat, right? Yes, but only to a degree. You can't simply dump extra fuel in and expect good results, because engines rely on having the proper air/fuel ratio to run efficiently. Generally, the air/fuel ratio will fall between 12:1 and 14.7:1. Simply adding more fuel to an engine (without increasing the airflow) will cause a rich condition, and that kills power. The key is to add more fuel as well as more oxygen.
We can feed an engine more fuel by raising the fuel pressure, enlarging the injector size, or by commanding the computer (in EFI applications) to do so. However, increasing the airflow is not always a simple task. Racers and hobbyists often install larger carburetors, ported intakes, heads and larger camshafts to increase airflow, while others bolt on a supercharger or turbocharger, which forces compressed air into the engine. In contrast, nitrous oxide boosts power only by increasing the oxygen content available to the engine, and by matching the oxygen with additional fuel we see increased power. That's why nitrous has been termed "atmosphere in a bottle."
Nitrous is stored in a pressurized bottle and is fed through a line to a solenoid, usually located near the engine. When the solenoid is energized, nitrous flows to the engine and is injected either near the throttle body, under the carburetor by a plate system, or directly into the ports in the intake manifold. Additional fuel is either supplied by the injectors or by supple-mental lines connected to a solenoid, which activates in sync with the nitrous solenoid.
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NOS, one of the leading manufacturers of nitrous systems, is a staple at the track and on the street. Nitrous bottles can be bolted in the trunk (as here in this Cobra roadster), hatch, or even in the driver's compartment when properly secured and vented. The beautiful thing about using nitrous on a street car is the system can be turned off so you can maintain stock-type drivability. |
Before any kit is installed you should consider the condition of the engine, including the internal components. If you plan to get into heavy nitrous use, it is recommended you install strong rods and forged pistons. This also applies to supercharger and turbocharger guys. |
On EFI engines, the nitrous can be injected directly into the intake tract. A tuning tip when using nitrous is to retard the timing to prevent detonation. One rule of thumb is you should take out 2 1/2 degrees for every 50 hp of nitrous. Most of the aftermarket ignition companies sell electronic switches to retard the timing when the nitrous is activated. This allows you to keep the timing at your normal setting for those times when the nitrous is not in use. |
The Nitrous Works offers a variety of systems. One is this outfit that uses a nozzle to inject the nitrous and the gas. It is not unusual to see gains up to 150 hp using a system like this. |
Fogger systems inject nitrous and gas directly into each intake port. A fogger should be used in race applications and can kick up the power by about 500 ponies. |
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Wilson Manifolds and Nitrous Pro Flow developed this plate system with burst panels. The burst panels are designed to blow out in the case of a nitrous backfire, thus preventing damage to the intake, carb, or throttle body. |
NOS makes this trick kit for Modular Ford engines. |
Maintaining proper fuel and nitrous pressure is critical, so a set of quality gauges is a must. |