Fuel Pressure Requirements For Nitrous: How Much Is Enough?

Nitrous oxide systems are designed to use a combination of fuel and nitrous jets based on specific nitrous and fuel pressures. This is because reducing either fuel or nitrous pressure lowers the total flow. Therefore, fuel pressure is critical. With a closed-end or dead-head nitrous fuel system, the fuel pump pushes fuel up against a closed valve when the fuel solenoid is not activated, increasing the line pressure and causing fuel pressure creep. Most fuel pumps have an internal bypass that is set to a given pressure, usually higher than the nitrous fuel system flowing pressure. When the nitrous system is activated and the fuel solenoid opens, the pressure drops significantly. This is why nitrous fuel pressure must be set by creating system fuel flow.

Fuel pressure creep

To understand fuel pressure creep, it's essential to know the difference between blocking-style and bypass-style fuel pressure regulators. In a blocking-style regulator, fuel enters through the inlet port, passes the fuel control valve, and is distributed through an outlet port to the carburetor. The fuel flow and pressure are controlled by the fuel control valve, which is actuated by a diaphragm. On the other hand, a bypass-style regulator has a fuel return line from the regulator back to the fuel tank. When there is no fuel demand, the fuel bypass valve redirects the fuel flow back to the tank instead of halting it completely, as in the blocking-style regulator.

Bypass-style regulators do not experience pressure creep because the fuel continues to flow even when the valve is closed. In contrast, pressure creep in blocking-style regulators can cause inconsistent fuel pressure readings, making it challenging to adjust the fuel pressure accurately.

To avoid pressure creep when adjusting fuel pressure with a blocking-style regulator, it is necessary to maintain a small amount of fuel flow through the regulator during adjustments. This can be achieved by operating the engine at idle speed or by using bleed returns to simulate flow rate.

In conclusion, fuel pressure creep is a critical factor to consider when working with blocking-style fuel pressure regulators. By understanding its causes and effects, one can take appropriate measures to mitigate its impact and ensure accurate and consistent fuel pressure adjustments.

Nitrous fuel system

A nitrous oxide engine, or nitrous oxide system (NOS), is an internal combustion engine that uses nitrous oxide (N2O) to burn fuel at a higher-than-normal rate, resulting in increased engine power output. The system can be ""dry,", where nitrous oxide is injected separately from the fuel, or "wet", where additional fuel is carried into the engine along with the nitrous.

The amount of fuel pressure required for a nitrous system depends on various factors, including the jet size, engine modifications, and desired power output. It is essential to follow the manufacturer's recommendations for fuel pressure to ensure optimal performance and prevent engine damage. Most users recommend maintaining a fuel pressure between 4 and 10 PSI for nitrous systems, with lower pressures preferred to avoid over-fuelling. However, the specific fuel pressure can vary depending on the nitrous kit and jetting setup being used.

Dedicated fuel pressure regulators are often used in nitrous systems to ensure stable fuel pressure. It is crucial to monitor fuel pressure while the nitrous system is active to prevent engine damage due to insufficient fuel delivery. Some users also employ a safety device called a Hobbs switch, which shuts off the nitrous if the fuel pressure falls below a certain threshold.

Additionally, it is important to consider the fuel delivery method when designing a nitrous fuel system. The four main methods are single nozzle, direct port, plate, and bar. Each method has advantages and disadvantages in terms of precision, ease of installation, and reversibility. The choice of delivery method depends on factors such as the type of fuel injection, desired power output, and ease of installation.

Nitrous pressure gauge

Benefits of Nitrous Pressure Gauges

The inclusion of a nitrous pressure gauge in your setup provides several advantages. Firstly, it allows you to easily monitor your vehicle's nitrous pressure, ensuring you maintain optimal bottle pressure. This monitoring capability helps prevent serious engine damage by allowing you to fine-tune your setup. Additionally, the pressure sensor included with the gauge can be installed directly into your nitrous system, regardless of the tank's location in your vehicle. This provides accurate readings that are displayed on the electronically driven nitrous gauge.

Installation and Customization

Nitrous Pressure Recommendations

The recommended fuel pressure for nitrous systems varies depending on the specific setup and jetting. Some sources suggest that a fuel pressure of around 5 to 7 PSI is typical for carbureted engines with nitrous, while others recommend 10 PSI for low-pressure jetting. It's important to consult the instructions and requirements of your specific nitrous kit to determine the optimal fuel pressure for your setup.

Flowing fuel pressure

With a closed-end or dead-head nitrous fuel system, the fuel pump pushes fuel up against a closed valve when the fuel solenoid is not activated, increasing the line pressure and causing fuel pressure creep. Most fuel pumps have an internal bypass set to a given pressure, usually higher than the nitrous fuel system flowing pressure. When the nitrous system is activated and the fuel solenoid opens, the pressure drops significantly. This is why nitrous fuel pressure must be set by creating system fuel flow.

To set the fuel pressure, you must flow fuel through the regulator. You cannot properly set a dead-headed regulator. Fuel pressure changes are a method of leaning or enriching your tune as needed based on plug reading and the incrementals on your time slip.

To properly use and tune a nitrous system, you need a fuel flow tool and an accurate nitrous pressure gauge in the car. The flow tool is used to flow fuel through the regulator to accurately set the fuel pressure and make changes. When it comes to nitrous pressure, a four-inch nitrous pressure gauge in the car is recommended. This way, regardless of what nitrous bottle is put in the car, it is always set to the same gauge.

Fuel flow tool

Fuel pressure is a critical aspect of a nitrous system, as too much or too little can lead to engine damage. To ensure the correct fuel pressure, a fuel flow tool is necessary.

The Nitrous Pro-Flow Pro Series Fuel Flow Tool is one such tool that can help set the correct flowing fuel pressure. It does so by attaching to the #6 fuel feed line, with the other end fitted with the appropriate size slip fit fuel/nitrous jet. The fuel supply is then turned on, and the fuel pressure is adjusted while the fuel flows through the tool and into a separate container. This process ensures that the fuel pressure is optimal for when the nitrous system is activated. The tool is highly accurate, with a margin of error of only 0.5%.

Another option is the Induction Solutions Flow Tool, which also includes safety features like an inline shut-off valve. This tool comes with a .073 jet already installed and a protective case. It is essential to have the correct gauge port adapters and fittings for your specific setup.

Nitrous Outlet also offers a Flowing Fuel Pressure Test Gauge Kit, which includes a digital gauge with high accuracy and 43 tuning jets. This kit provides an exact readout, allowing for fine-tuning adjustments with confidence. The gauge can measure fuel pressure in low or high-pressure fuel systems and has a programmable auto-shutoff feature.

When using nitrous, it is crucial to follow the kit instructions and maintain the recommended fuel pressure to avoid engine damage. The jetting setup, dome, compression, nozzle, and other factors also play a role in optimising nitrous systems.

Frequently asked questions