Fuel Pressure Regulator Club 3G: What You Need To Know

The Mitsubishi Eclipse 3G Club is an online forum community for Mitsubishi Eclipse 3G owners and enthusiasts. Members discuss modifications, troubleshooting, engine swaps, maintenance, and more. One such discussion centres on the fuel pressure regulator (FPR) and whether it is necessary to install one. Some members suggest that it is a relatively inexpensive part that could save your motor, while others advise on specific FPRs to purchase and how to install them.

The Aeromotive FPR

When installing the Aeromotive FPR, it is important to remove the stock FPR completely. The fuel flow will then go from the tank to the fuel rail, out to the Aeromotive FPR (one side port, the other side blocked off), and then return to the tank via the bottom port. This setup allows the Aeromotive FPR to function correctly and maintain the desired fuel pressure.

Some users have also suggested using the open port on the Aeromotive FPR to attach a fuel pressure gauge. This can provide a more accurate monitoring of fuel pressure, especially if the gauge is installed inside the cabin. Additionally, when mounting the Aeromotive FPR, it is recommended to have it right side up, as per the instructions.

Overall, the Aeromotive FPR appears to be a reliable option for Mitsubishi Eclipse 3G owners looking to upgrade their fuel pressure regulator and ensure optimal fuel flow and pressure for their modified engines.

The stock FPR

When installing an aftermarket FPR, you will need to remove the stock FPR completely. The fuel flow will then go from the tank to the fuel rail, out to the FPR (one side port, the other side blocked off), and then return to the tank via the bottom port. The FPR controls the amount of fuel returned to the tank, creating higher or lower pressure in the fuel system.

It is important to note that the stock fuel pump may not be sufficient for a Fuel Management Unit (FMU). An upgraded fuel pump, such as the Walbro 255lph, may be necessary to ensure adequate fuel delivery.

The FPR and FMU

The Fuel Pressure Regulator (FPR) is a component in a car's fuel system that controls the amount of fuel that is returned to the tank. It works by restricting the flow of fuel, thereby increasing the pressure in the fuel system. The stock FPR on a Mitsubishi Eclipse 3G is located at the end of the fuel rail and has a vacuum line connected to it.

Some car enthusiasts choose to upgrade or replace the stock FPR, especially when modifying their car for performance or installing a turbo kit. This is because the stock FPR may not be able to handle the increased fuel demands of a modified engine or turbo setup, potentially leading to insufficient fuel pressure or lean fuel mixtures.

When upgrading the fuel system, there are a few options to consider:

• Fuel Pressure Regulator (FPR): This is a basic component that allows you to adjust the base fuel pressure. However, it does not increase fuel pressure relative to boost, so it may not be sufficient for a turbocharged engine.
• Rising Rate Fuel Pressure Regulator (RRFPR): This is an adjustable FPR that includes a vacuum line. It can increase fuel pressure with boost, but it may not provide enough fuel for high-boost applications.
• Fuel Management Unit (FMU): An FMU is a more advanced option that includes both a FPR and a fuel pressure booster. It adds a set amount of fuel pressure for every psi of boost, ensuring an adequate fuel supply for turbocharged engines. There are adjustable and non-adjustable FMUs available, with the non-adjustable options being considered more reliable.
• Electronic Tuning Devices and Larger Injectors: Instead of solely relying on fuel pressure, you can also increase fuel delivery by upgrading to larger injectors and using an electronic tuning device to fine-tune the fuel delivery. This option may be more expensive but can provide more precise control over fuel delivery.

When choosing between these options, it's important to consider your specific needs and budget. For a mildly modified car, a simple FPR upgrade might be sufficient. For a turbocharged setup, an FMU or a combination of larger injectors and electronic tuning may be more appropriate. It is always a good idea to consult with experienced mechanics or tuning specialists to ensure that your fuel system is properly configured and safe.

The FPR vacuum line

The Fuel Pressure Regulator (FPR) vacuum line is responsible for maintaining the appropriate fuel pressure in the engine. It connects the FPR to the intake manifold, allowing the FPR to adjust fuel pressure based on the engine's vacuum or boost pressure. This ensures a consistent and adequate fuel supply, optimizing engine performance and fuel efficiency.

When it comes to the FPR vacuum line, Mitsubishi Eclipse 3G owners often face a dilemma. The stock FPR is designed to handle up to 10 PSI, and attempting to use it beyond this limit can lead to performance issues. Upgrading to an aftermarket FPR becomes necessary, especially when installing performance modifications such as turbo kits or larger fuel injectors.

Aftermarket FPRs, such as the Aeromotive A1000-6, offer greater flexibility and performance. However, they require careful installation and consideration of other components in the fuel system. Braided stainless steel fuel lines are often recommended for their durability and performance, but they can be challenging to install, especially when connecting to the fuel rail. Custom-made fuel lines or professional assistance may be required to ensure a proper fit.

Additionally, the FPR vacuum line plays a crucial role in boost control. When running a turbocharger, connecting the FPR vacuum line becomes essential. It allows the FPR to adjust fuel pressure in relation to the manifold pressure, ensuring the engine receives the necessary fuel to support the increased boost levels. This 1:1 ratio of fuel pressure to manifold pressure helps prevent running lean or rich, optimizing performance and engine safety.

In conclusion, the FPR vacuum line is a critical component for Mitsubishi Eclipse 3G owners, especially those seeking performance enhancements. Upgrading the FPR and associated fuel lines can improve engine performance and fuel efficiency. However, careful consideration and installation are required to ensure the system functions correctly. For those with turbochargers, the FPR vacuum line becomes even more vital, ensuring the engine receives the fuel it needs to handle the increased boost levels safely.

The FPR and fuel injectors

Fuel injectors are devices that spray pressurised fuel into the engine's combustion chamber, intake manifold, or throttle body. They play a critical role in the final stage of fuel delivery, ensuring that the fuel is atomised and mixed with air before combustion. The performance of fuel injectors is influenced by factors such as fuel pressure and injector size.

When upgrading an engine's fuel system, the relationship between the FPR and fuel injectors is important. Increasing fuel pressure by installing a higher-rated FPR can impact fuel injector performance. Higher fuel pressure may require larger or higher-flow fuel injectors to ensure optimal fuel delivery and engine performance. Conversely, upgrading to larger fuel injectors may necessitate adjusting the FPR to provide the optimal fuel pressure for the new injectors.

In some cases, installing a 3-bar FPR (increasing fuel pressure) instead of larger fuel injectors may be a more cost-effective option. However, this approach can lead to decreased fuel efficiency as the higher fuel pressure may result in increased fuel consumption. Additionally, the engine management system or chip must be calibrated to accommodate the higher fuel pressure to ensure proper fuelling and engine performance.

Ultimately, the decision to upgrade the FPR or the fuel injectors depends on various factors, including engine specifications, desired performance, and cost considerations. Consulting with a qualified technician or mechanic is advisable to ensure that the FPR and fuel injectors are appropriately matched and calibrated for optimal engine performance and fuel efficiency.

Frequently asked questions