What NOS Means in Cars

NOS in a car most commonly refers to Nitrous Oxide Systems—the brand name of a popular performance parts company—used generically to describe nitrous oxide (N2O) injection for a temporary horsepower boost. In parts catalogs and restoration circles, NOS can also mean New Old Stock, referring to original, unused factory components. Understanding the context clarifies which meaning applies.

In Performance Talk: Nitrous Oxide Systems

When enthusiasts say a car “has NOS,” they typically mean it’s equipped with a nitrous oxide injection system. Nitrous oxide increases engine power by adding more oxygen (released when N2O decomposes under combustion heat) and cooling the intake charge, allowing more fuel to be burned safely for a short burst of extra power. The term originates from Nitrous Oxide Systems, a brand founded in the late 1970s and now part of Holley Performance, whose kits popularized nitrous in street and track applications.

How Nitrous Adds Power

Mechanically, nitrous injection provides a denser, oxygen-rich charge and lowers intake temperatures, enabling a controlled increase in fuel and spark energy. This yields significant, on-demand gains—from mild 25–75 horsepower shots to 300+ horsepower on race setups—when properly tuned.

The following components are commonly found in a complete nitrous kit and help explain how the system operates:

• N2O bottle and heater: Stores nitrous under pressure; a heater stabilizes pressure for consistent flow.
• Solenoids: Electrically controlled valves that meter nitrous and (in “wet” systems) additional fuel.
• Jets or nozzles/plate: Calibrated orifices that determine the “shot” size and mix location.
• Feed lines and fittings: High-pressure plumbing to safely deliver nitrous to the intake.
• Controller or window switch: Manages activation by RPM, throttle position, and gear for safety.
• Safety devices: Blow-down tube, pressure relief disc, and wideband monitoring to prevent damage.

Together, these parts ensure nitrous is introduced in the right amount and at the right time, safeguarding the engine while delivering the intended power increase.

Common System Types

Nitrous systems vary in how they add fuel and where they introduce the mixture. Choosing the right type depends on goals, engine build, and tuning capability.

• Dry system: Injects only nitrous; the ECU or fuel system adds extra fuel via injectors. Simpler, often used on EFI cars.
• Wet single-nozzle/plate: Adds nitrous and fuel together before the intake manifold. Balanced and popular for street/strip.
• Direct-port: Individual nozzles for each cylinder with separate fuel and nitrous lines. Most precise and scalable for high power.

Each setup trades complexity for control; dry systems are easiest to install, while direct-port builds offer the safest, most even distribution at higher power levels.

Safety, Tuning, and Legality

Proper installation and calibration are essential to avoid detonation and engine damage. Equally important are local regulations governing street use and bottle transport.

• Tuning: Use appropriate jetting, ignition timing retard, and sufficient fuel supply; verify air-fuel ratios with a wideband sensor.
• Hardware checks: Maintain bottle pressure (typically 900–1,050 psi), inspect lines/solenoids, and use filters.
• Engine readiness: Healthy compression, cooling, and spark components are critical before adding nitrous.
• Compliance: Track use is widely accepted; street legality varies by jurisdiction. Transport rules may require a closed valve and safety caps.

When treated as a complete system—mechanical, electronic, and regulatory—nitrous can be a reliable power adder rather than a risk.

In Parts and Restorations: New Old Stock

Outside performance discussions, NOS can mean New Old Stock: original, unused parts produced by the manufacturer or its suppliers years ago, typically prized for authenticity in restorations. These items differ from reproductions or aftermarket equivalents.

Consider the following when evaluating NOS parts for a project:

• Authenticity and fit: NOS parts often match factory specs and finish, aiding concours-level restorations.
• Condition: Age can affect rubber, plastics, and coatings even if parts are unused; inspect carefully.
• Availability and cost: Scarcity can drive prices high; weigh originality against budget and function.
• Compatibility: Verify part numbers and model-year applicability to avoid mismatches.

Choosing NOS parts can enhance historical accuracy and value, but practicality and condition should guide the final decision.

Pop Culture and the Name

Movies and games helped turn “NOS” into a catch-all term for nitrous, even when the hardware isn’t made by Nitrous Oxide Systems. While the brand’s role is foundational, using “nitrous” is the clearer, generic descriptor for the power-adder itself.

Summary

In car culture, NOS most often refers to Nitrous Oxide Systems, the brand synonymous with nitrous oxide injection used to deliver short bursts of power. In parts contexts, NOS stands for New Old Stock, meaning original, unused factory components. Context—performance talk vs. parts sourcing—determines which meaning applies.

What does NOS do to a car?

NOS (nitrous oxide) gives a car more power by introducing a concentrated source of oxygen into the engine, allowing for a more efficient and powerful combustion of fuel. The N₂O molecules break apart under engine heat and pressure, releasing extra oxygen. This process also has a cooling effect, making the intake air denser, which further allows more fuel to be burned, resulting in a short but significant increase in horsepower. 
How it works

1. Oxygen Delivery: Nitrous oxide contains two parts nitrogen and one part oxygen. When injected into the engine, it acts as a temporary oxygen booster. 
2. Temperature and Pressure: In the hot engine cylinder, the stable nitrous oxide molecules split apart, releasing the oxygen to burn with the fuel. 
3. Fuel Combustion: The increased amount of oxygen allows the engine to burn more fuel more quickly and efficiently. 
4. Cooling Effect: As the liquid nitrous oxide expands into a gas, it cools down, making the air entering the engine denser and allowing even more fuel to be burned. 
5. Increased Power: The combination of extra oxygen and denser air leads to a bigger, more powerful explosion during the combustion cycle, which results in increased horsepower. 

Effects on the Car

• Increased Horsepower: Opens in new tabNOS provides a temporary boost in engine power, often used for short bursts during racing. 
• Faster Acceleration: Opens in new tabThe added power allows the car to accelerate more quickly. 
• Potential for Engine Damage: Opens in new tabWhile effective, improperly tuned nitrous systems can lead to a lean air-fuel mixture, which can damage the engine. 
• Increased Wear: Opens in new tabOver time, the increased stress on engine components like the pistons, connecting rods, and gaskets can lead to accelerated wear and potential failure. 

Why is NOS illegal in a car?

NOS is not federally illegal in cars, but many states prohibit its use on public roads due to safety risks, potential for street racing, increased pollution, and the risk of engine damage. While NOS systems are legal for track use in many states, using them on the street is often illegal, as laws vary significantly by location and can range from completely prohibiting them to restricting their use to private property or race tracks. 
Reasons for Legal Restrictions

• Safety Hazards: Nitrous oxide can be dangerous if inhaled, and its high-pressure application in an engine can lead to explosive failures if improperly installed or used. 
• Engine Stress and Damage: The sudden increase in oxygen and power from NOS can overstress engine components, potentially causing engine failure like blown head gaskets or damaged pistons. 
• Illegal Street Racing: NOS is a popular modification for street racing, and lawmakers often ban it to discourage and combat illegal activities on public roads. 
• Pollution Concerns: Using NOS increases pollution, as it adds nitrogen to the engine’s combustion cycle, which can increase emissions beyond legal limits. 

Legal Status and Where to Find Information 

• Vary by State: Opens in new tabWhile the federal government doesn’t ban NOS in cars, many state laws strictly regulate or prohibit it.
• Legal for Racing: Opens in new tabMany states allow the use of NOS in vehicles specifically for racing on a closed track.
• On-Public-Road Restrictions: Opens in new tabSome laws only prohibit having the system connected or ready for use on public roads, requiring it to be disconnected or safely stored in the trunk.
• Research Your Local Laws: Opens in new tabIt’s crucial to research the specific laws in your state and consult with local auto enthusiasts or professionals to understand what is permitted.

In summary, while not federally illegal, NOS use in a car is often illegal on public roads due to a combination of safety risks, potential for engine damage, and association with illegal street racing.

What does NOS mean for a car?

NOS (Nitrous Oxide System) is a forced induction system for cars that temporarily boosts an engine’s power by injecting nitrous oxide (N₂O) into the intake. The nitrous oxide, stored as a liquid in a tank, turns into a gas when released, cooling the air in the intake and delivering more dense oxygen to the engine. This additional oxygen allows more fuel to be burned, significantly increasing horsepower for a short duration.
 
How it works:

1. Storage: Nitrous oxide is stored as a liquid in a high-pressure cylinder. 
2. Injection: When activated, a solenoid valve releases the liquid nitrous oxide into the engine’s intake manifold. 
3. Gasification & Cooling: As the liquid nitrous oxide turns into a gas, it absorbs heat, cooling the incoming air. 
4. Increased Oxygen: The gaseous nitrous oxide decomposes, releasing oxygen (which is 36% of its weight) and nitrogen. 
5. Enhanced Combustion: This extra oxygen, far denser than what’s in normal air, allows the engine to burn more fuel. 
6. Power Boost: More fuel burned results in more power and a significant, but temporary, increase in horsepower. 

Types of NOS Systems:

• Dry System: Opens in new tabOnly nitrous oxide is injected into the intake manifold, and the car’s standard fuel system is adjusted to provide more fuel. 
• Wet System: Opens in new tabBoth nitrous oxide and additional fuel are mixed together before being injected into the engine. 

Key Considerations:

• Finite Resource: Nitrous oxide is a consumable resource that needs to be refilled. 
• Engine Preparedness: Engines must be tuned to handle the increased pressure and heat that comes with using a nitrous system. 
• Legality: While not federally illegal, state and local laws may restrict the use or storage of nitrous oxide in vehicles. 
• Temporary Boost: NOS provides a short burst of power, making it ideal for racing or high-performance applications. 

How much does NOS increase speed?

Nitrous oxide (NOS) increases engine speed and power by providing more oxygen for combustion, which can add from 50 to several hundred extra horsepower, depending on the engine and system setup. While this boosts acceleration and can help a car reach its potential top speed faster, it won’t significantly increase a vehicle’s maximum speed, which is limited by the car’s gearing and rev limiter. 
How Nitrous Works 

1. Phase Change: Liquid nitrous oxide (N₂O) turns into a gas when released into the engine’s intake, causing a significant drop in temperature and a resulting increase in the density of the air/oxygen mixture entering the cylinders.
2. More Oxygen, More Fuel: The extra oxygen allows for the combustion of more fuel, leading to a powerful burst of additional horsepower and torque.
3. Short Bursts: NOS systems are designed for short, powerful bursts of power, rather than continuous use.

Factors Influencing Power Gains

• Engine Size and Type: Opens in new tabLarger engines and forced-induction (turbocharged/supercharged) engines can typically handle and benefit from larger nitrous “shots” more effectively than smaller, naturally aspirated engines. 
• Nitrous System Setup: Opens in new tabThe size of the “shot” (the amount of nitrous injected) and the type of system (e.g., dry vs. wet, direct port vs. fogger) directly impact the resulting horsepower increase. 
• Internal Engine Components: Opens in new tabFor significant power gains, engine components like pistons, connecting rods, and gaskets may need to be upgraded to withstand the increased stress. 

Impact on Speed

• Faster Acceleration: Opens in new tabThe significant increase in power allows the vehicle to accelerate to its maximum speed much faster. 
• No Increased Top Speed (Usually): Opens in new tabIn most cases, nitrous will not raise a car’s theoretical top speed, as this is capped by the engine’s gearing and rev limiter. However, if the car’s top speed was previously limited by insufficient power to reach the longest gear at redline, nitrous can help it reach a higher top speed.