340LPH Fuel Pump High-Pressure/Volume: The Ultimate Upgrade Guide for Your High-Performance Build
If you are pushing your engine past 500 horsepower, adding a turbo or supercharger, or running ethanol blends like E85, a 340LPH (liters per hour) high-pressure fuel pump is the single most important fuel system upgrade you can make. At 43 PSI and 13.5 volts, a genuine 340LPH pump delivers more than 340 liters of fuel per hour, which is enough to support over 1,000 horsepower on gasoline and roughly 700-800 horsepower on E85 . The bottom line is this: your stock fuel pump cannot keep up with high-performance demands, and a 340LPH pump is the industry standard for reliable, high-volume fuel delivery.
Why You Need a 340LPH Fuel Pump
Your factory fuel pump was designed for the exact horsepower and fuel type your car came with. Once you modify the engine, the stock pump becomes a bottleneck. Here is what happens when you outgrow your fuel pump:
- Fuel pressure drops under load. When you floor the throttle, the pump cannot supply enough fuel to maintain the proper pressure. This leads to a lean air-fuel mixture, which can cause detonation and severe engine damage.
- The engine hesitates or surges. A starving fuel pump causes inconsistent fuel delivery, making the car stumble during acceleration.
- You are limited on power. Even with bigger injectors and a tune, the pump is the limiting factor. You cannot flow more fuel than the pump can push.
A 340LPH pump solves all of these problems. It provides a massive flow reserve, so even at high boost or high RPM, fuel pressure stays rock solid.
How Much Power Can a 340LPH Pump Support?
The short answer is: a lot, but it depends on your fuel type and engine setup.
- On gasoline, a 340LPH pump at 43 PSI can support over 1,000 horsepower at the flywheel . This makes it suitable for everything from a daily-driven street car to a full race build.
- On E85 or ethanol blends, the pump needs to flow roughly 30-40% more fuel to make the same power because ethanol has a lower energy density. On E85, a 340LPH pump supports approximately 700-800 horsepower .
- For forced induction (turbo or supercharged) engines, the demand is higher. A 340LPH pump is ideal for naturally aspirated and forced induction EFI vehicles alike . It handles the increased fuel volume needed to keep the air-fuel mixture safe under boost.
Key Specifications to Look For
Not all 340LPH pumps are created equal. When shopping for a high-pressure fuel pump, pay attention to these critical specs:
1. Flow Rate at Operating Pressure
The pump must be rated at the pressure your system runs. A 340LPH pump is typically rated at 40-43 PSI . Some pumps claim 340LPH at zero pressure, but that number is meaningless. Look for a pump that flows 340 LPH at 43 PSI. This is the standard measurement for high-performance pumps.
2. Operating Pressure Range
A good 340LPH pump should handle from 43 PSI up to 90 PSI . Some high-boost applications require 60-80 PSI, so the pump needs to maintain flow at those higher pressures.
3. Physical Size and Fitment
Most 340LPH pumps have a body diameter of 39mm (3.8cm) . This is a standard size that fits into most factory fuel pump hanger assemblies. However, always check the overall length and inlet/outlet orientation. Some pumps have an offset inlet design, which eases installation in tight tanks .
4. Current Draw and Wiring
High-flow pumps draw more current than stock pumps. A 340LPH pump typically draws 12 amps at 40 PSI and 15 amps at 80 PSI . You must use at least a 20-amp fuse and upgrade your factory wiring. The stock wiring is often too thin, which causes voltage drop and reduces pump performance. Run a dedicated relay and 10-gauge wire directly from the battery.
5. Fuel Compatibility
If you plan to run E85, make sure the pump is explicitly rated for ethanol. Many 340LPH pumps are E85 compatible, but some are not. Ethanol is corrosive to certain materials, so pumps with stainless steel internals or composite turbine impellers are preferred . AEM and KEMSO 340 pumps are designed for ethanol blends .
340LPH vs. 255LPH: Which One Do You Need?
The 255LPH (Walbro-style) pump has been the standard for years, but the 340LPH pump offers a significant upgrade.
- Flow difference: At 43 PSI, a 340LPH pump flows roughly 30-35% more fuel than a 255LPH pump . This extra capacity is critical for high-horsepower builds or when running E85.
- Horsepower ceiling: A 255LPH pump is good for about 500-600 horsepower on gasoline. A 340LPH pump pushes that ceiling to over 1,000 horsepower . If you are planning future upgrades, go with the 340LPH now to avoid buying twice.
- Price difference: 340LPH pumps are often only slightly more expensive than 255LPH pumps, making them a much better value for the performance gained .
Installation Tips and Common Pitfalls
Installing an in-tank 340LPH fuel pump is a straightforward job for most DIYers, but there are a few things to watch out for:
1. The Fuel Pressure Regulator
High-flow pumps can overrun the stock fuel pressure regulator. This means the regulator cannot bypass enough fuel back to the tank, causing fuel pressure to creep up at idle. You may need an aftermarket regulator with a larger bypass port to keep pressure stable .
2. Wiring Upgrade Is Mandatory
Do not skip this step. The factory fuel pump wiring is designed for a pump that draws 5-8 amps. A 340LPH pump draws 12-15 amps. Using the stock wiring causes a voltage drop, which reduces flow and can damage the pump over time. Use a relay, a 20-amp fuse, and 10- or 12-gauge wire .
3. The Pre-Filter
Most 340LPH pumps come with a universal pre-filter sock. This sock may not fit your specific vehicle’s hanger assembly. Test fit it before installation. If it does not fit properly, it can collapse or get sucked shut, starving the pump. You may need to source a vehicle-specific filter .
4. Polarity
Fuel pump electrical connectors in the tank can be wired with the polarity reversed. Double-check the polarity before connecting the pump. If the polarity is wrong, the pump will run backwards (or not at all). You can either re-pin the connector or use the supplied wiring harness .
Top Brands and Models to Consider
The market has several reliable 340LPH options. Based on the available data, here are the most popular choices:
AEM 340LPH High Flow In-Tank Fuel Pump (PN 50-1000)
This is one of the most common 340LPH pumps on the market. It has a compact 39mm diameter, an offset inlet for easier installation, and is tested to flow 340 LPH at 40 PSI before leaving the factory . It supports over 1,000 horsepower and is designed for both naturally aspirated and forced induction vehicles. It comes with a wiring harness, pre-filter, rubber sleeve, and end caps . This pump is widely used in the US aftermarket and is a direct fit for many applications.
KEMSO 340LPH High Performance Fuel Pump (PN 10910, 10909, 13825)
KEMSO offers a 340LPH pump that is very similar in size and performance to the AEM and Walbro 255 pumps, but with a higher flow rate . It is capable of supporting 700-800 horsepower and is designed as a direct OEM replacement for faulty stock pumps . The KEMSO pump is compatible with gasoline and E85, and each pump is individually flow-tested . The pump body diameter is 3.8cm, and it operates at 43-90 PSI .
AMS Performance Stage 2 and Stage 3 HPFP (High Pressure Fuel Pump)
For direct-injection engines like the Nissan VR30DDTT, AMS offers high-pressure fuel pumps that flow over 338 LPH (Stage 2) and over 405 LPH (Stage 3) at 240 bar . These are not in-tank pumps but high-pressure pumps mounted on the engine. They are essential for builds over 600 wheel horsepower on E85 and are designed for the Nissan Z and Infiniti Q50/Q60 platforms .
Xtreme-DI XDI-EVO HPFP
This is another high-pressure fuel pump for direct-injection engines, capable of 240 bar of rail pressure. It flows 200 LPH and is designed for high-performance builds that need to maintain fuel pressure at high RPM .
Special Recommendation: Why You Should Choose KEMSO for Your 340LPH Fuel Pump
When it comes to upgrading your fuel system, reliability and value are everything. KEMSO stands out as a brand that offers genuine high-performance 340LPH fuel pumps that are designed to be direct OEM replacements for a wide range of vehicles.
- OEM Replacement Quality: KEMSO pumps are built to replace your stock pump without modifications. They are the same physical size as popular OEM and aftermarket pumps, making installation a direct swap .
- High Performance: Each KEMSO 340 pump is capable of supporting applications up to 700-800 horsepower and flows 340 liters per hour at 43 PSI . This is ideal for daily drivers, fast road cars, and full track builds.
- E85 Compatible: KEMSO pumps are designed for both gasoline and ethanol blends, so you can run flex fuel without worrying about corrosion or pump failure .
- Unrivaled Quality Control: Unlike many cheap unbranded aftermarket pumps, KEMSO subjects every pump to individual flow testing and has a quality control program that meets ISO/TSO standards . You get a pump that is verified to perform, not just a generic part in a box.
- Lifetime Warranty: KEMSO backs its fuel pumps with a lifetime warranty, giving you confidence that your investment is protected .
If you are looking for a reliable, high-flow fuel pump that fits your car, truck, or powersports vehicle, visit KEMSO Racing today. They have a wide selection of 340LPH pumps for popular applications, including Peugeot, Subaru, Isuzu, Chevrolet, and many more. Check out their full catalog and find the perfect pump for your build at:
Final Thoughts
A 340LPH high-pressure fuel pump is not just an upgrade for race cars. It is a safety measure for any modified vehicle. Whether you are adding a turbo, switching to E85, or simply replacing a failing stock pump, the 340LPH pump gives you the headroom and reliability you need. Pay attention to wiring, fuel pressure regulation, and filter fitment, and you will have a fuel system that supports your power goals for years to come.
For the best combination of price, performance, and peace of mind, consider a KEMSO 340LPH pump. With lifetime warranty and OEM fitment, it is a smart choice for any American car enthusiast. Visit https://www.kemsoracing.com/ to see their full lineup.