Introducing COBB CAN Flex Fuel for the 2023+ Subaru Ascent and Outback!

At COBB, we have been adding Flex Fuel tuning to Subarus for nearly a decade.  Our NexGen module and fuel system upgrades are track tested and make adding flex fuel to EJ-powered Subarus truly turn-key.  Subaru’s transition to direct injection for the 2015+ WRX and all supported 2019+ Ascent/Outbacks with the FA24 motor means a slightly different implementation when it comes time for flex fuel. Our CAN Gateway Flex Fuel solution was first introduced to for the 2015-2021 WRX in mid-2024 followed by the latest generation VB WRX receiving CAN Flex Fuel in early 2025.

Luckily for us, Subaru uses a similar ECU strategy across all of their vehicles powered by the FA24F in 2023 onward.  This means we are able to carry over a lot of custom features initially developed for the WRX over to the Ascent, Outback, and Legacy!

Vehicles Supported

This implementation of COBB CAN Flex Fuel is applicable to the following vehicles.  Note that it is NOT currently compatible with earlier year 2019-2022 vehicles. 

2023 Subaru Ascent CVT USDM
2023 Subaru Legacy Sport CVT USDM
2023 Subaru Legacy XT CVT USDM
2023 Subaru Outback Wilderness CVT USDM
2023 Subaru Outback XT CVT USDM
2024 Subaru Ascent CVT USDM
2024 Subaru Legacy Sport CVT USDM
2024 Subaru Legacy XT CVT USDM
2024 Subaru Outback Wilderness CVT USDM
2024 Subaru Outback XT CVT USDM
2025 Subaru Ascent CVT USDM
2025 Subaru Legacy Sport CVT USDM
2025 Subaru Legacy XT CVT USDM
2025 Subaru Outback Wilderness CVT USDM
2025 Subaru Outback XT CVT USDM

What Is Flex Fuel?

First, let’s cover exactly what it is we’re talking about here.  Flex Fuel is the term given to a vehicle’s ability to utilize fuel with varying levels of ethanol content.  Most pump fuel these days uses “up to 10% ethanol” and in some areas you can find pumps with full blown E85.  While we aren’t going to get into the initial reasoning behind the push for fuels with higher ethanol, we ARE going to touch on one of its benefits – power.  Fuel with higher ethanol content burns faster in the combustion chamber, absorbs more heat, and ends up with an effective Octane rating of ~100-105, dependent upon the actual ethanol content.  The advantage of these factors to us is that we can take advantage of them to make a considerable amount of power when compared to standard E10 fuel.

How Does It Work?

Adding flex fuel to these vehicles is straight forward.  First, you install one of our CAN Flex Fuel Kits into your car’s engine bay.  These kits include an Ethanol Content Sensor, Fuel Pressure Sensor, and our CAN Gateway which relays sensor data to the ECU.  Once that sensor data is available to the ECU, an Accessport based tune can take that data and make changes to how the engine is running to best utilize the ethanol content present.

Why Do You Want It?

As we touched on earlier, the benefit of using fuel with higher ethanol content in this case is to increase the power output of your Ascent or Outback’s engine.  Subaru’s 2.4L Direct Injection motor responds VERY well to tuning with ethanol.  The dyno graph and power gains chart below just how much the FA24 can be “turned up” over stock.  The lowest set of lines (black & gray) represent factory power and torque output. The colored lines represent power output at either end of the spectrum of ethanol content with the lower set representing E10 (normal pump 93 octane) and the higher set an Ascent/Outback on full E85.

We offer two flavors of Flex Fuel enabled OTS Maps for these applications.  Choose the file that best matches your base fuel, either 91 or 93 octane.

Stage1+FlexFuel 91
Stage1+FlexFuel 93

For a full breakdown of COBB Off The Shelf Maps, their parts & fuel requirements, and expected power output please visit our Map Notes Page.

Sounds Great, What Do I Need?

The power increases from our previously mentioned Off The Shelf Maps are possible thanks to working seamlessly with our all new CAN Flex Fuel Parts & Packages compatible with the 2023-2025 Subaru Ascent, Outback, and Legacy.  These are available to purchase in a couple of different ways, depending on your existing modification level – either a full Stage 1 + Flex Fuel Power Package or any of the individual parts needed to get your car to that level.

COBB CAN FLEX FUEL UPGRADE ASCENT / OUTBACK / LEGACY 2023-2025

The COBB CAN Gateway Flex Fuel Upgrade offers true plug-and-play installation and allows for seamless integration of flex fuel for the 2023-2025 Subaru Ascent, Outback, and Legacy.

CAN Gateway

The included COBB CAN Gateway provides the means for aftermarket sensor data to be injected into your car’s CAN system where it can be absorbed by the ECU and utilized in either a COBB Off The Shelf Map or custom calibration. The Gateway itself is constructed of billet aluminum encasing a precision manufactured PCB. The included bracket allows for a straight-forward bolt-in installation on supported cars.

Vehicle Specific Harness

Each CAN Gateway Kit includes a vehicle specific wiring harness. This specific kit is compatible with 2023-2025 Ascent, 2023-2025 Outback XT/Wilderness, and 2023 Legacy XT / Sport. It is comprised of a bespoke cable which runs into the cabin and utilizes our CAN adapter, allowing integration to be a plug-and-play affair. Installation of this component requires removal of your car’s Radio/Cockpit Control Unit.

CAN Ethanol Sensor Kit

The CAN Ethanol Sensor Kit includes an ethanol sensor with mounting bracket, fuel lines with quick connect fittings, and a wiring harness that connects to the CAN Gateway.

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SUBARU CAN FUEL PRESSURE SENSOR KIT WRX 2022-2025, ASCENT / OUTBACK / LEGACY 2023-2025

A plug and play solution when using the COBB CAN Gateway enabling users to monitor low side Fuel Pressure on a Custom Accessport monitor.  The Fuel Pressure Sensor Kit is REQUIRED when using COBB Stage 1+ Flex Fuel OTS Maps.

The Fuel Pressure Sensor Kit uses OEM quality connectors, making fit and finish second to none. Included in this kit is a 0-100psi Fuel Pressure Sensor, a bespoke quick-connect billet adapter, and a wiring harness that allows for plug-and-play installation with the COBB CAN Gateway.

Select this product if you already have our Stage 1 Package (Accessport and High Flow Filter) for your Ascent, Outback, or Legacy.  Adding these components to your existing configuration will upgrade your car to be able to use our new Stage 1 + CAN Flex Fuel OTS Maps.

INCLUDES:

CAN Flex Fuel Upgrade
CAN Fuel Pressure Sensor Kit

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The Stage 1+ CAN Flex Fuel Power Package includes it all.  Dollar for dollar, this is the easiest and cheapest way to add over 55hp and 65tq to your otherwise stock Ascent, Outback, or Legacy!

INCLUDES:

Accessport V3
COBB High Flow Panel Filter
CAN Flex Fuel Upgrade
CAN Fuel Pressure Sensor Kit

SUBARU CAN FLEX FUEL CUSTOM TUNING

For cars that fall outside the support of COBB OTS Maps, look to our network of Protuners.  Tuning any Subaru on E85 is possible! Our Subaru Accesstuner Pro HL custom tuning software now includes full tuning support for CAN Flex Fuel.

FIND A COBB PROTUNER HERE