SPOOL FX-350 Upgraded High-Pressure Fuel Pump (HPFP) – Mercedes-AMG M157

What Is the Spool FX-350?

The Spool FX-350 is a next-generation upgraded high-pressure fuel pump designed specifically for the Mercedes-AMG M157 5.5L V8 biturbo engine. Engineered to support high-horsepower applications, the FX-350 delivers increased fuel flow and pressure capabilities to overcome the limitations of the factory high-pressure fuel system.

With operating pressure capabilities of up to 350 BAR, the FX-350 provides the additional fueling capacity required for aggressive performance builds, higher ethanol concentrations, and larger turbocharger setups.

Designed with performance and reliability in mind, the FX-350 is engineered to support demanding fueling requirements while maintaining factory-style integration.

Why Do You Need the FX-350?

The factory M157 high-pressure fuel pumps become a significant limitation when increasing engine output, particularly when running high ethanol blends or upgrading to larger turbochargers.

As horsepower increases, so does the demand for fuel delivery. The factory HPFP system can struggle to maintain the required fuel pressure and volume under high-load conditions.

The Spool FX-350 addresses these limitations by providing:

• Increased high-pressure fuel delivery capacity.
• Operating pressure capability of up to 350 BAR.
• Improved fueling support for high-horsepower applications.
• Greater flexibility when running E50, E85, and other ethanol blends.
• Additional fueling headroom for upgraded turbocharger systems.
• Increased fuel system capability for aggressive custom tuning.

Whether you're building a high-horsepower street car or pushing your M157 platform to its limits, the FX-350 is designed to take your fuel system to the next level.

What Does the Kit Include?

The Spool FX-350 fuel system package is designed to provide the necessary components for upgrading your factory high-pressure fueling system.

• 2 × Spool FX-350 upgraded high-pressure fuel pumps.
• Upgraded fuel lines and necessary installation hardware.
• Additional supporting fuel system components, depending on selected package configuration.

350 BAR High-Pressure Fuel Technology

One of the defining features of the FX-350 is its ability to support fuel pressures up to 350 BAR.

Higher fuel pressure capability provides additional flexibility when configuring direct-injection fueling strategies. This allows your tuner to optimize injection pressure, injector delivery, and injection timing around your engine's specific performance requirements.

Combined with increased pump flow capacity, the FX-350 provides a stronger foundation for high-output M157 builds.

E85 Compatibility

The FX-350 is designed to support ethanol-based fueling applications, including E85.

Ethanol blends require significantly more fuel volume than traditional pump gasoline. As a result, upgraded high-pressure fueling capacity becomes increasingly important as engine output rises.

The FX-350 helps provide the additional fueling capacity needed for high-ethanol applications while supporting the demands of aggressive performance calibrations.

Are Tune Changes Required?

YES. Custom tuning and fuel system calibration are required.

The FX-350 requires appropriate ECU calibration changes to account for the upgraded pump characteristics and increased fuel delivery capabilities.

These changes must be completed before starting the engine with the upgraded pumps installed. Operating the vehicle without the appropriate calibration can result in improper fuel system operation and potential component damage.

Spool Performance can provide the necessary pump calibration information to your existing tuner and assist with technical questions regarding integration.

Custom tuning is strongly recommended to maximize performance, maintain proper fueling, and ensure the system is calibrated for your specific vehicle, turbocharger configuration, fuel type, and operating conditions.

Spool Performance specializes in fuel system hardware and does not provide custom ECU tuning.

Supporting Low-Pressure Fuel System Upgrades

Upgrading the high-pressure fuel pumps is only one part of building a capable direct-injection fuel system.

Proper low-pressure fuel delivery is critical to the performance, lubrication, and long-term durability of the high-pressure pumps.

Insufficient low-pressure fuel supply can cause fuel starvation, excessive pump wear, and damage to the internal piston and bore assemblies.

For this reason, we strongly recommend evaluating your factory low-pressure fuel system and upgrading supporting components when necessary to ensure adequate fuel supply under demanding operating conditions.

A properly matched low-pressure and high-pressure fuel system is essential for achieving consistent fueling performance and protecting your investment.

Built for Serious M157 Performance

The Spool FX-350 is designed for enthusiasts and builders who have outgrown the limitations of the factory M157 fuel system.

Whether you're running upgraded turbochargers, high-ethanol fuel blends, or pursuing serious horsepower goals, the FX-350 provides the increased fuel pressure and delivery capability needed to support your build.