Best Fuel Pumps for E85 Subaru STI Performance

Alright, fellow Subaru STI enthusiasts, let’s talk fuel! If you’re anything like me, you’ve probably caught the E85 bug. The performance gains, the cooler running temperatures – it’s all incredibly tempting, especially for our turbocharged beasts. But before you dive headfirst into running ethanol, there’s a crucial component you must upgrade: your fuel pump. Believe me, I’ve seen firsthand what happens when a stock pump tries to keep up with E85’s higher demand; it just starves the engine, and that’s a recipe for disaster. I’ve spent my fair share of time under the rear seat of an STI, swapping pumps and chasing down fuel issues, so I know a thing or two about what works. In this guide, we’re going to dive deep into some of the best fuel pumps available for your E85 Subaru STI performance build, comparing their features, real-world benefits, and helping you make an informed decision for your ride.

IMAGE	PRODUCT NAME	AMAZON LINK
	KEMSO 340LPH High Performance Fuel Pump for Subaru Legacy…	View on Amazon
	AEM 50-1215 E85-Compatible High Flow In-Tank Fuel Pump…	View on Amazon
	KEMSO 340LPH High Performance Fuel Pump for Subaru/Honda…	View on Amazon
	KEMSO 340LPH High Performance Fuel Pump for Subaru/Honda…	View on Amazon
	KEMSO 340LPH High Performance Fuel Pump for Subaru/Honda…	View on Amazon

KEMSO 340LPH High Performance Fuel Pump for Subaru Legacy…

When you’re pushing serious power through your STI, you need a fuel pump that won’t flinch. The KEMSO 340LPH pump is designed exactly for that, providing a robust solution for enthusiasts running E85. What really stands out is its USA-based support and a lifetime warranty, which gives a huge peace of mind when dealing with such a critical component. This pump is built to handle the higher demands of ethanol fuels and significantly boosts fuel delivery over stock, making it a solid choice for heavily modified setups. It’s truly engineered to keep your engine fed, whether you’re daily driving or hitting the track.

Key Features:
– Supports up to 600 BHP in N/A, Turbocharged, and Supercharged applications
– Kemso Support for our pumps is USA based and provided by USA technicians
– Designed for gasoline or E85
– Bypass valve set at 125.8psi, higher than both GSS series 255LPH pumps, and 400/ 450LPH pumps
– Serialized fuel pump body guarantees Lifetime warranty. Kemso has built its reputation on providing a lifetime warranty for all its OEM and performance fuel pumps

Pros:
– Excellent flow rate for high horsepower E85 applications
– Robust bypass valve maintains stable fuel pressure
– Lifetime warranty offers exceptional long-term security
– USA-based technical support is a big plus for troubleshooting
– E85 compatible right out of the box

Cons:
– Installation might require some basic wiring and mechanical skills
– Can be slightly louder than the stock pump, as is common with performance units

Best for: Enthusiasts targeting up to 600 BHP on E85, who value a strong warranty and reliable USA-based support.

User feedback summary: Many users report this pump as a straightforward, reliable upgrade that delivers consistent fuel pressure and flow, making their E85 tunes run smoothly without hiccups. The lifetime warranty is frequently highlighted as a major confidence booster.

AEM 50-1215 E85-Compatible High Flow In-Tank Fuel Pump

The AEM 340lph E85-Compatible High Flow In-Tank Fuel Pump is a well-regarded name in the performance world, and for good reason. AEM is known for its quality and this pump lives up to that reputation, offering consistent performance for both naturally aspirated and forced induction setups. What’s particularly impressive is that every single pump is flow-tested to 340 LPH at 40 PSI before it leaves the factory, assuring you of its performance right out of the box. Its compact size makes installation a bit easier in tight spaces, and it comes with a comprehensive kit to help you get the job done right. This pump is truly versatile, ready for almost any high-performance fuel you throw at it.

Key Features:
– Designed for in-tank mounting on high performance naturally aspirated and forced induction vehicles
– Includes a wiring harness, pre filter and O-rings
– Every AEM 340lph E85-Compatible Fuel Pump is tested to flow 340 lph at 40 PSI before it is packaged for sale
– Tested and compatible with ethanol fuels up to E100, methanol fuels up to M100 and all types of gasoline
– Compact body (39mm diameter x 65mm length)
– Includes pre filter, hose, clamps, flying lead, end cap and rubber buffer sleeve
– Fit type: Vehicle Specific

Pros:
– Highly reputable brand known for quality
– Individually tested for guaranteed flow rate
– Excellent compatibility with various fuels, including E100 and M100
– Compact size can simplify installation
– Comes with a complete installation kit, minimizing extra purchases

Cons:
– Does not offer a lifetime warranty like some competitors
– Priced slightly higher than some other 340LPH options

Best for: Tuners who prefer a well-established brand, value factory-tested performance, and need a pump compatible with a wide range of ethanol and methanol fuels.

User feedback summary: Owners appreciate the AEM pump’s consistent performance and the peace of mind that comes with individual testing. The included installation kit is often mentioned as a helpful bonus, making the swap smoother.

KEMSO 340LPH High Performance Fuel Pump for Subaru/Honda…

This KEMSO 340LPH pump, like its sibling reviewed above, continues the brand’s commitment to high-performance fuel delivery, specifically designed with Subaru and Honda applications in mind. It shares the same robust specifications, capable of supporting up to 600 BHP on a variety of fuel types, including E85. The key selling point here remains the serialized body guaranteeing a lifetime warranty, showcasing Kemso’s confidence in their product’s durability. For those looking for consistent fuel pressure and flow for their E85 setup, this pump provides the necessary upgrade with the added benefit of USA-based customer support. It’s a reliable workhorse for serious builds.

Key Features:
– Supports up to 600 BHP in N/A, Turbocharged, and Supercharged applications
– Kemso Support for our pumps is USA based and provided by USA technicians
– Designed for gasoline or E85
– Bypass valve set at 125.8psi, higher than both GSS series 255LPH pumps, and 400/ 450LPH pumps
– Serialized fuel pump body guarantees Lifetime warranty. Kemso has built its reputation on providing a lifetime warranty for all its OEM and performance fuel pumps

Pros:
– High flow rate suitable for high-power E85 applications
– Exceptional lifetime warranty
– Strong bypass valve for consistent fuel pressure
– USA-based support for quick assistance
– Proven E85 compatibility

Cons:
– May require some minor modifications for a perfect fit in some vehicles
– Like most performance pumps, it’s not as silent as an OEM unit

Best for: Subaru and Honda owners seeking a high-flow, E85-compatible pump for up to 600 BHP, backed by a strong warranty and customer support.

User feedback summary: Many users report seamless installation and immediate improvements in fuel delivery, especially for their E85 tunes. The lifetime warranty is frequently cited as a major factor in their purchase decision and overall satisfaction.

KEMSO 340LPH High Performance Fuel Pump for Subaru/Honda… (Another Variant)

Yet another strong contender from KEMSO, this 340LPH pump is essentially identical in its core performance to the other KEMSO units we’ve looked at, providing the same dependable high-volume fuel delivery required for E85-tuned Subaru STIs. The crucial elements like 600 BHP support, the 125.8psi bypass valve, and the lifetime warranty are all present, making it a very appealing option. It’s designed to provide ample fuel for demanding turbocharged applications and ensures that your engine gets the consistent flow it needs to prevent leaning out under boost. This is a consistent, quality offering within the Kemso lineup.

Key Features:
– Supports up to 600 BHP in N/A, Turbocharged, and Supercharged applications
– Kemso Support for our pumps is USA based and provided by USA technicians
– Designed for gasoline or E85
– Bypass valve set at 125.8psi, higher than both GSS series 255LPH pumps, and 400/ 450LPH pumps
– Serialized fuel pump body guarantees Lifetime warranty. Kemso has built its reputation on providing a lifetime warranty for all its OEM and performance fuel pumps

Pros:
– Consistent high flow for significant power gains on E85
– Outstanding lifetime warranty
– Built-in USA support is a great bonus
– Robust pressure regulation
– Excellent value for the features provided

Cons:
– Fitment can be tight in some older Subaru models without minor bracket adjustments
– Expect a slight increase in pump noise compared to factory

Best for: Budget-conscious performance enthusiasts who need E85 compatibility and high flow up to 600 BHP, backed by a leading warranty.

User feedback summary: Users highlight the pump’s great performance for the price, noting its reliability for E85 conversions and modified engines. The lifetime warranty frequently comes up as a deciding factor, offering long-term confidence.

KEMSO 340LPH High Performance Fuel Pump for Subaru/Honda… (Final Variant)

Rounding out our KEMSO selection, this final 340LPH High Performance Fuel Pump offers the same impressive specifications and reliability that we’ve come to expect from the brand. If your Subaru STI is running E85 and making serious power, this pump is more than capable of handling the demands, supporting up to 600 BHP. The lifetime warranty and USA-based support are cornerstones of Kemso’s offering, ensuring you’re not left stranded. This consistency across their 340LPH line means you’re getting a proven design that’s specifically engineered to deal with the corrosive nature of ethanol fuels while maintaining optimal fuel pressure and flow.

Key Features:
– Supports up to 600 BHP in N/A, Turbocharged, and Supercharged applications
– Kemso Support for our pumps is USA based and provided by USA technicians
– Designed for gasoline or E85
– Bypass valve set at 125.8psi, higher than both GSS series 255LPH pumps, and 400/ 450LPH pumps
– Serialized fuel pump body guarantees Lifetime warranty. Kemso has built its reputation on providing a lifetime warranty for all its OEM and performance fuel pumps

Pros:
– Ideal flow rate for up to 600 BHP on E85
– Unbeatable lifetime warranty
– Reliable USA-based customer service
– High-pressure bypass valve for stable delivery
– Durable construction for E85 use

Cons:
– Like most aftermarket pumps, some users report a louder hum than stock
– Requires careful installation to ensure proper sealing and wiring

Best for: Any Subaru STI owner seeking a robust and reliable E85-compatible fuel pump with an industry-leading warranty for their performance build.

User feedback summary: Many reviews praise the pump for its consistent performance and easy installation, especially when replacing older, weaker pumps. The lifetime warranty is consistently mentioned as a standout feature that provides long-term value.

Helpful Comparison Insights

When choosing the best fuel pumps for E85 Subaru STI performance, you’ll primarily be weighing the robust offerings from KEMSO against the well-established reputation of AEM.

The KEMSO 340LPH pumps (all three “Subaru/Honda” variants and the “Subaru Legacy” one, as they share identical core features) are essentially the same high-performing unit. Their standout feature is undoubtedly the lifetime warranty, which provides immense confidence, especially for a component that sees so much stress with E85. They’re all rated to support up to 600 BHP, which covers a significant range of modified STIs. The USA-based support is also a huge plus, offering direct help if you ever need it. For many, the Kemso pumps offer incredible value for their E85 performance capabilities and the peace of mind of that warranty.

On the other hand, the AEM 340LPH pump brings the weight of a highly respected brand in the performance automotive world. While it doesn’t offer a lifetime warranty, AEM’s commitment to quality is evident in their practice of individually flow-testing every single pump before it ships. This means you know exactly what you’re getting in terms of performance. The AEM pump also boasts compatibility with E100 and M100 fuels, making it a more versatile choice for extreme applications or those dabbling in different race fuels. Its compact body and included comprehensive installation kit can also make the installation process a bit smoother for some users.

If your primary concern is long-term reliability and an unbeatable warranty for up to 600 BHP on E85, the KEMSO pumps are an incredibly strong contender. You’re getting a proven design with excellent support. However, if you prefer the reassurance of individual factory testing, a well-known brand name, and potentially broader fuel compatibility (like methanol), then the AEM pump is an excellent choice. Both are solid 340LPH options that will adequately feed your E85-tuned STI, but their core value propositions are slightly different.

Final Verdict

Choosing the right fuel pump for your E85 Subaru STI is a critical decision, and after looking at these options, it’s clear there are some excellent choices. For most STI owners looking to reliably run E85 and support up to 600 BHP, the KEMSO 340LPH series offers incredible value. The consistent performance, coupled with that standout lifetime warranty and USA-based support, makes it a very compelling package that’s hard to beat for long-term peace of mind.

However, if you’re someone who values the prestige and proven individual testing of a major brand, and perhaps you have plans for even more exotic fuels beyond E85, then the AEM 340LPH pump is an equally fantastic choice. It delivers on performance and comes with a full installation kit, which is a nice touch.

Ultimately, you can’t go wrong with any of these 340LPH pumps for your E85 Subaru STI performance build. Just be sure to match your pump choice with your power goals, your personal preference for brand reputation versus warranty, and ensure you have all the necessary supporting mods (like larger injectors and a proper tune!) to make the most of your new fuel pump.

FAQ Section

Q1: Why do I need an upgraded fuel pump for E85 on my Subaru STI?
A1: E85 (ethanol) requires approximately 30-40% more fuel volume than gasoline for the same power output. A stock fuel pump simply can’t deliver enough fuel to meet this demand, leading to dangerous lean conditions that can damage your engine, especially under boost. An upgraded fuel pump, like the best fuel pumps for E85 Subaru STI performance reviewed here, ensures your engine receives adequate fuel.

Q2: What “LPH” means and how much do I need for my E85 STI?
A2: LPH stands for Liters Per Hour, which is a measure of the fuel pump’s flow rate. For most E85 Subaru STI builds targeting moderate to high horsepower (e.g., 400-600 BHP), a 340LPH pump is generally considered the minimum and a highly recommended upgrade. Always consult with your tuner to confirm the exact LPH requirement for your specific power goals.

Q3: Is installation of these fuel pumps difficult for an average DIYer?
A3: Installing an in-tank fuel pump on a Subaru STI typically involves accessing the fuel pump assembly under the rear seat. While not overly complex, it does require basic mechanical skills, some specific tools (like a fuel line disconnect tool), and careful attention to detail for wiring and sealing. If you’re unsure, it’s always best to have a professional shop perform the installation.

Q4: Do I need a tune after installing an upgraded fuel pump for E85?
A4: Absolutely, yes! Installing a higher-flowing fuel pump without a corresponding tune will cause your engine to run extremely rich, potentially leading to performance issues, fouled spark plugs, and even catalytic converter damage. A proper E85 tune is essential to adjust fuel maps for the increased flow and ethanol content, optimizing your Subaru STI performance.

Q5: What other modifications should I consider alongside an E85 fuel pump upgrade?
A5: To fully utilize E85 and an upgraded fuel pump, you’ll also need larger fuel injectors (as E85 requires higher volume), an E85-compatible fuel pressure regulator (if your stock one can’t handle the pressure), and potentially braided fuel lines or an upgraded fuel filter to handle the ethanol. Most importantly, a flex-fuel kit allows your car’s ECU to automatically adjust for varying ethanol content.

Q6: Are these E85 compatible fuel pumps louder than stock?
A6: Generally, yes. Performance fuel pumps like the KEMSO and AEM 340LPH units are designed for flow and pressure, not silence. While modern designs have reduced noise, you might notice a slightly louder “hum” from the rear of the car compared to your stock pump, especially at idle or low speeds. It’s a common trade-off for enhanced E85 Subaru STI performance.