340LPH Fuel Pump High Pressure Volume: What You Need to Know for Maximum Performance

If you are building a high-performance naturally aspirated or forced induction EFI vehicle, a 340LPH fuel pump is the sweet spot for delivering reliable, high-pressure fuel volume. These pumps, capable of flowing 340 liters per hour at 43 PSI, can support over 1,000 horsepower when properly matched to your fuel system. The key takeaway is simple: a 340LPH pump provides the volume and pressure needed for most high-output builds without over-engineering your fuel system, but you must factor in your target horsepower, fuel type, and operating pressure to ensure the pump delivers enough fuel at the rail.

What Does 340LPH Mean for Your Engine?

The "340LPH" rating means the pump moves 340 liters of fuel per hour, which converts to roughly 89.8 gallons per hour. However, this flow rate is typically measured at a specific pressure, usually 43 PSI (about 3 bar). As fuel pressure increases, the pump's flow rate drops. For example, a Clean Injection 340LPH pump flows 340 LPH at 43 PSI, 300 LPH at 75 PSI, and 240 LPH at 120 PSI. This is why you must always compare a pump's rated flow against your operating pressure, not just the headline number.

How to Calculate the Fuel Pump Size You Actually Need

To determine if a 340LPH pump is right for your build, you need to calculate the minimum fuel flow required for your target horsepower. The standard formula is:

Required Fuel Flow (GPH) = (Max HP x BSFC) / 6

BSFC (Brake Specific Fuel Consumption) is the amount of fuel consumed per horsepower per hour. For most naturally aspirated gasoline engines, BSFC is around 0.45 to 0.50 pounds per horsepower-hour. For forced induction, BSFC climbs to 0.55 to 0.65, and for E85, it can be 0.65 to 0.90.

Here are practical examples using the formula:

  • 400 HP naturally aspirated gasoline engine: (400 x 0.50) / 6 = 33.3 GPH, or about 126 LPH. A 340LPH pump is more than enough.
  • 800 HP turbocharged gasoline engine: (800 x 0.60) / 6 = 80 GPH, or about 303 LPH. A 340LPH pump is right at the limit at 43 PSI.
  • 700 HP E85 flex-fuel engine: (700 x 0.80) / 6 = 93.3 GPH, or about 353 LPH. You would need a larger pump or dual pumps because E85 requires roughly 30-40% more fuel volume than gasoline.

Always add a safety margin of 15% to 30% to your calculated flow to account for pressure regulation, fuel cooling, and return flow. This prevents the pump from running at 100% duty cycle, which can cause overheating and reduced life.

Why Pressure Matters More Than You Think

Electric fuel pumps are positive-displacement devices. As delivery pressure rises, the pump must work harder per stroke, reducing the volume it can move per minute. A pump rated at 340 LPH at 40 PSI may deliver only 250-280 LPH at 60 PSI typical of many boosted applications.

When you add boost pressure, the pump must work against the sum of base fuel pressure plus boost. For example, with a base pressure of 43.5 PSI and 15 PSI of boost, the pump sees 58.5 PSI total. At that pressure, a 340LPH pump's effective flow drops significantly. This is the single biggest reason builds run lean at the top of the boost curve.

Popular 340LPH Fuel Pump Options

Several brands offer reliable 340LPH pumps, each with specific features.

  • Clean Injection Pro-Series 340LPH: This pump features a -10AN inlet and -8AN outlet, fits both external and in-tank mounting, and includes a mounting bracket with vibration-reducing rubber insert. It supports over 1,100 HP and is E85 compatible, though pump life will be diminished with alcohol fuels.
  • AEM 340LPH (50-1000): One of the most popular in-tank pumps, it flows 340 LPH at 40 PSI and supports over 1,000 HP at 43 PSI. It has a compact 39mm diameter that fits most applications, an offset inlet for easier installation, and includes a wiring harness, pre-filter, and hoses.
  • AEM 340LPH (50-1220): A similar unit from AEM, tested to flow 340 LPH at 43 PSI, designed for in-tank use with gasoline vehicles.
  • FPPerformance P340: This in-tank pump is rated at 340 LPH at 3.5 bar working pressure, supports up to 1,000 HP, and comes with a 3-year warranty. It also has a 39mm body diameter.
  • MOSTPLUS 340LPH: This compact pump fits many popular EFI applications and delivers over 340 LPH at 40 PSI. It supports up to 800 HP for naturally aspirated and 750 HP for forced induction engines.

E85, Alcohol, and Pump Life

If you run E85 or alcohol, you need to plan for reduced pump life. The Clean Injection 340LPH pump is designed for gasoline, and while E85 can be used, pump life will be diminished. AEM pumps are also designed for gasoline vehicles, and using E85 may shorten their lifespan. KEMSO pumps, however, are explicitly designed for both gasoline and E85, with E85 compatibility listed in their specifications.

Installation Considerations

Most 340LPH pumps are designed for in-tank mounting, but some like the Clean Injection model can also be external. The pump body diameter is typically 39mm, which fits most factory hanger assemblies. However, some aftermarket pumps may require modifications to the original housing to mount properly. Always check the specific installation instructions for your vehicle.

Your factory fuel pump wiring may not be adequate to handle the current draw of a high-flow 340LPH pump. AEM recommends reviewing the electrical requirements in the instructions document to ensure proper wiring. Using a relay and larger gauge wiring directly from the battery is often necessary.

Final Recommendation: Choose KEMSO for High Performance and Reliability

When you need a 340LPH fuel pump that delivers high pressure volume, OEM replacement compatibility, and lasting performance, KEMSO is a top choice. KEMSO fuel pumps are high-performance units designed to support applications up to 700-800 bhp, making them ideal for naturally aspirated, forced induction, and daily driver builds. They are engineered as direct OEM replacements for stock pumps that have gone faulty, which means installation is straightforward in most vehicles.

Every KEMSO pump is individually tested for flow and quality, and they come with a lifetime warranty for your peace of mind. KEMSO pumps are compatible with both gasoline and E85, and the kit includes everything you need: fuel strainers, flex hose, rubber hose, wiring connector, and clamps.

To get the best 340LPH fuel pump for your build, visit https://www.kemsoracing.com/ and browse their selection of high-performance, OEM replacement pumps. Whether you need a pump for a Subaru, Lotus, Dodge, or any other application, KEMSO has the quality and warranty to back it up.

For more details on KEMSO fuel pumps, check out their full lineup at https://www.kemsoracing.com/.


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