2018-2021 Subaru WRX STi 2.5L E85 Flex Fuel Conversion Kits
Boost your HP by up to 20% With our Plug-and-Play E85 Kits
In 2015, Subaru decided to focus their Rally Car efforts on the WRX STi sedan and we are here for it. The 4th and current generation of WRX STi still gets its speed from the 2.5L turbocharged 4-cylinder, capable of 310 horsepower but its suspension got a major overhaul. Reminiscent of the 2000-2007 Impreza WRX STi, the current generation has a much tighter turn with quicker steering and super sharp reflexes for sailing through the curves. Boost the horsepower by up to 20% with one of our WRX STi E85 flex fuel conversion kits and you have a real track contender.
No tuning required!
$699 List price $874Starting at $61.50 / month with 
SKU: U-EF-PLUS - Free shipping
- Delivery time 2-5 days
- 5 year warranty with registration
Introduction
The eFlexPlus and the eFlexPro are so easy to install that you can do it yourself in an afternoon and have your car running any mixture of E85 flex-fuel and standard gasoline the same day. Both come with a handy phone app that allows you to monitor the fuel mixture and switch between efficiency and performance profiles, effortlessly. The eFlexPro comes with the additional eFlexTuning software that allows you to tune your turbocharged engine on any mixture of fuel above E50. Order one of these for your 4th generation Subaru WRX STi today and increase your horsepower by up to 20%. Your HP can go from 310 to 370 ponies. That’s not bad for a couple of hours of “work”.
Installation
Plug&Play installation with some modifications - An experienced mechanic will install in 2-3h. For first time DIY installation, expect to double the time needed.
Technical specs
| Make & Model | Subaru WRX |
| Years | 2018-2021 |
| Engine | 2.5l / EJ257 |
| Power | 310 hp |
Always Optimized Fully Automatic Flex Fuel
Cooler & Cleaner Engine
Complete System, No Tuning Needed
Up to 10% Increase in Performance 
Your Fuel System VerifiedDIY Virtual Load Sensor Tuning
Easily & safely create custom ethanol fuel maps based on your own vehicle's performance & modifications, without tapping into external load sensors - all from your laptop. Now you can augment your Ethanol fueling yourself, without touching your factory ECU and without jeopardizing engine safety.
Experience the VelvetTouch+
All eFlexFuel devices provide smoother and more seamless drivability than any other flex fuel system in existence. No small feat, our R&D team accomplished this with unrivaled attention to detail, countless long days & late nights, and a unique eye for optimization. The result of this "Velvet Touch" development? Our class-defining eFlexPro 2 & eFlexPlus.
Supercar Technology in your Daily Driver (or Weekend Warrior)
By installing the eFlexFuel kit, you're in good company. eFlexFuel conversion kits utilize technology found in the Koenigsegg Jesko, Dodge Challenger SRT Demon 170, and other top-tier performance vehicles. This tech is used to get the most out of E85, Gasoline, or whatever blend of the two you have in your tank.
Industry Leading, Free 5-Year Warranty (With product registration)
Nothing says, "We stand behind our product," like our free 5-Year warranty. We know what our kits are made of and we aren't afraid to put our money where our mouth is. You will not find a warranty like this anywhere else.
Expertly Engineered, Designed & Manufactured in Finland
Expertly Engineered, Designed & Manufactured in Finland. We have developed our hardware & software in-house in Pirkkala, Finland, since day one. Before shipping, we confirm every single control unit's functionality before shipping.
Technical Specs & Features
- Precise Ethanol Content real-time measured over 100 times per second
- Advanced signal processing filtering system in all input signals
- Shock-Proof & Weather proof casing
- High Quality Wiring Harness with snap in connectors (no soldering required)
- Ethanol Tested & Approved fuel accessories (line, clamps, quick-connectors)
- Bluetooth 5.2
eFlexApp Main Features
Dynamic Gauge Screen
with Key Information
Choose Your Driving Mode
Dyno Proven Power Gain
Real-time Analog Data
for Sensor Inputs
Log History
with Real-Time Parameters
Please confirm device versions features at eFlexApp page
eFlexTuner Main Features
3D Fuel Maps
With eFlexFuel's Pro models, fuel maps can be observed in the 3D graphics window. The view can be rotated freely and selected fuel map cells are highlighted over the 3D map. The color-coded fuel map makes analysis simple.
Data Logging
All running parameters of the control unit can be captured and saved to a log file. Choose which parameters to display including date range. eFlexPro and eFlexMoto Pro log files can be analyzed in-depth with the eFlexTuner. Color-coding helps distinguish data points. (For example, the fuel mixture or the injector duty cycle.)
Log File Analysis
eFlexPro and eFlexMoto Pro log files can be analyzed in depth with the eFlexTuner. Data can be taken from an entire session or a specific timespan. The data is color-coded, which helps to distinguish e.g., the fuel mixture or the injector duty cycle.
Please confirm device versions features at eFlexTuner page
+ Compare products
 |  | |
|---|---|---|
| Features | ||
| VelvetTouch+ | ||
| Free 5-Year Warranty (with registration) | ||
| Ethanol Content real-time measured over 100 times per second | ||
| Advanced signal processing filtering system in all input signals | ||
| Shock-Proof & Weather Proof casing | ||
| High Quality Wiring Harness with snap in connectors (no soldering required) | ||
| Ethanol Tested & Approved fuel accessories (line, clamps, quick-connectors) | ||
| Bluetooth 5.2 | ||
| Analog Wires for External Sensors | ||
| eFlexApp | ||
| Ethanol content | ||
| Engine RPM | ||
| Duty cycle | ||
| Fuel temperature | ||
| Ambient engine temperature | ||
| Injector activity | ||
| Cold enrichment | ||
| Device status | ||
| Driving mode selection | ||
| Cold enrichment custom setting (created with eFlexTuner) | ||
| Save RPM based enrichment with driving mode selection (created with eFlexTuner) | 1 | 3 |
| eFlexPro view for analog data | ||
| eFlexTuner | ||
| RPM. based 2D fuel map | ||
| Fault codes | ||
| Data logging | ||
| Fuel map adjustment | ||
| Log file analysis | ||
| 3D fuel maps | ||
| Sensor linkage | ||
| Cold start adjustment | ||
| Virtual Load Sensor Tuning |
+ What's included
+ Installation
+ Returns
+ Warranty
Testimonial
What's included in the eFlexPro E85 flex fuel conversion kit / Installation
Note: If your car is modified you can use E85 with eFlexFuel. If this is the case, please list all the main engine modifications on the checkout page. Our technical team will ensure that your setup is fit for E85.
* Power and torque increase depends on your engine technology and/or your custom built of the engine.
Not legal for sale or use on pollution-controlled vehicles