Cobb Previous Ethanol Sensor Kit to CAN Flex Fuel Upgrade — 2015-2017 Subaru WRX
The Cobb CAN Flex Fuel Kit with Fuel Pressure Kit — Upgrade from Previous Sensor for the 2015-2017 Subaru WRX FA20DIT upgrades an existing earlier-generation Cobb ethanol sensor installation to the current CAN-based system, enabling real-time ethanol content communication via the CAN bus for dynamic flex fuel calibration. Requires an Accessport V3 with CAN Flex Fuel OTS maps loaded.
DETAILS
- Platform: 2015-2017 Subaru WRX FA20DIT
- CAN-based ethanol sensor: measures actual ethanol content in real time
- Fuel pressure sensor included
- Enables Accessport CAN Flex Fuel OTS maps for dynamic calibration
- Works with E10 through E85 and any blend in between
- Requires Accessport V3 with CAN Flex Fuel map capability
- Upgrade from previous sensor kit
How Flex Fuel Works on Subaru
Cobb’s CAN Flex Fuel system uses an ethanol content sensor installed in the fuel line to measure the actual ethanol percentage of whatever fuel is in the tank at any given time — whether it is straight pump E85 (typically 70-85% ethanol), E30, E40, any custom blend, or straight 93-octane gasoline. This measurement is sent to the Accessport via the CAN bus, and the Accessport ECU map adjusts fueling, ignition timing, and boost targets automatically based on the real ethanol content — not based on which OTS map slot the driver selects, but based on what the sensor actually reads. This means an owner can run any blend of ethanol and gasoline without switching maps or worrying about whether the current map matches the fuel. The ECU dynamically adjusts for the fuel being used.
CAN System, OTS Maps, and Ethanol Blends
Ethanol provides two performance advantages over gasoline that the flex fuel system exploits. First, ethanol has a much higher effective octane rating than pump gasoline — this allows more aggressive ignition timing advance without risk of detonation. Second, ethanol has a high latent heat of vaporization — it absorbs a significant amount of heat when it evaporates in the intake manifold and combustion chamber, cooling the intake charge and further reducing knock tendency. Together, these properties allow the flex fuel OTS maps to target meaningfully higher boost levels and more aggressive timing than the equivalent 93-octane gasoline maps. The real-world result is a substantial power increase on E30 or higher ethanol blends over what the same engine produces on 93 octane. The flex fuel system makes this power increase accessible without requiring the driver to maintain a specific fuel blend or manually switch calibrations — the system adapts automatically to whatever is in the tank.
What’s in the Box
- CAN flex fuel ethanol sensor
- Fuel pressure sensor and fittings
- Fuel line fittings and hardware
- Installation instructions
Why Choose Cobb Tuning
Cobb Tuning has been developing performance software and hardware for turbocharged enthusiast vehicles since 1999. Founded in Austin, Texas, Cobb built its reputation on the Accessport and expanded into a full catalog of hardware engineered to complement it. Every OTS map is developed in-house on real vehicles, and every hardware product is validated as part of a complete system — not sourced and sold in isolation. That integrated approach is why Cobb produces consistent, reliable results across the builds we see every day.
The RallySport Take
The Cobb CAN Flex Fuel system for the 2015-2017 Subaru WRX FA20DIT gives Accessport-equipped owners the ability to run any ethanol blend — from 93 octane through E30, E50, and full E85 — with the Accessport automatically adjusting the calibration for the measured fuel composition. The ethanol sensor reads the blend in real time, and the CAN bus communicates that reading to the Accessport ECU map continuously. The driver does not need to know or track the exact ethanol percentage — the system handles it. Requires an Accessport V3 with the appropriate CAN Flex Fuel OTS maps for the platform.
Fitment
| Year | Make | Model | Notes |
|---|---|---|---|
| 2015-2017 | Subaru | WRX | FA20DIT — upgrade from previous sensor kit |
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