Subaru NexGen Flex Fuel


NexGen Flex Fuel is finally here.  Today we are extremely excited to release the first phase of NexGen Flex Fuel support for our Subaru platform here at COBB, covering USDM 2015-2021 WRX STI.  This release consists of an all new NexGen Flex Fuel Ethanol Content Sensor Kit, Stage Power Packages with supporting Off The Shelf Maps, and support in Accesstuner Pro for custom tuning.  COBB NexGen Stage 2 + Flex Fuel Stage Power Packages and Off The Shelf Maps have undergone and passed third party emissions / reasonable basis testing and are currently available in 49 states as we continue to seek a CARB EO.

The Flex Fuel Kits

Introducing NexGen Stage 2 + Flex Fuel Power Packages!  These power packages are based upon our 50-state legal NexGen Stage 2 Power Packages, simply adding NexGen Flex Fuel into the mix by way of our all new ethanol content sensor kit and fuel pressure sensor kit.  For 2015-2021 STI there are three flavors of the package, the difference being which intake is included.  All three of these Power Packages are supported by COBB Off The Shelf Maps.

NexGen Stage 2 + Flex Fuel Power Package 2015-2018 STI (SF Intake)

NexGen Stage 2 + Flex Fuel Power Package 2019-2021 STI, 2018 STI Type RA (SF Intake)

NexGen Stage 2 + Flex Fuel Redline Carbon Fiber Power Package 2015-2021 STI, 2018 STI Type RA


At the heart of NexGen Flex Fuel is our all new module and harness solution.  This module takes signal from the ethanol content sensor placed in your car’s fuel line and converts it into something that the ECU can then comprehend and utilize to make calibration changes on the fly to account for any change in ethanol concentration.

NexGen Stage 2  to Nexgen Stage 2+ Flex Fuel Upgrade Package

This upgrade package is all that is necessary for those who are already taking advantage of our 50-State Legal NexGen Stage 2 Power Package.  With the supporting fuel system already handled within that package, all that is needed in order utilize our supporting Off The Shelf Map are the two sensor kits below for ethanol content and fuel pressure.


NexGen Flex Fuel Module + Harness Kit

For those who were utilizing our previous Flex Fuel components, this upgrade package is all you would need in order to move into the NexGen product line.  Your existing COBB fuel rails, lines, and ethanol content sensor configuration can be retained.  This kit includes the bare necessities; an all new NexGen module and plug-and-play harness.


Power Package Upgrade Kits

If you are already utilizing a COBB Stage Power Package and want to move into a NexGen Flex Fuel Power Package, we have you covered!  The packages below are available for vehicles that are currently in a Stage 1 or Stage 1+ (intake) configuration.

From current Stage 1 (Accessport re-used)


From current Stage 1 + Intake (Accessport + Intake re-used)


Off The Shelf Maps and Power Gains

These map files are only available to be downloaded from the Maps section of the COBB website.  Download Flex Fuel Off The Shelf Maps HERE.

  • NexGen Stage2 1050x + Flex 91 v510 HWG.ptm
  • NexGen Stage2 1050x + Flex 91 v510 LWG.ptm
  • NexGen Stage2 1050x + Flex 91 v510.ptm
  • NexGen Stage2 1050x + Flex 93 v510 HWG.ptm
  • NexGen Stage2 1050x + Flex 93 v510 LWG.ptm
  • NexGen Stage2 1050x + Flex 93 v510.ptm
  • NexGen Stage2 1050x + Flex ACN91 v510 HWG.ptm
  • NexGen Stage2 1050x + Flex ACN91 v510 LWG.ptm
  • NexGen Stage2 1050x + Flex ACN91 v510.ptm

This dyno graph shows the ranges of horsepower and torque that you can expect to experience when using the COBB NexGen Stage 2 + Flex Fuel Power Package and accompanying OTS map. Using 93 octane with up to E10, our development car made a peak of 307 whp and 338 wtq., exactly what you’d expect to make on a normal NexGen Stage 2 Power Package. Then, without changing a single part on the car and using the exact same tune, we bumped the ethanol percentage in the tank up to E65 where the car made a peak of 332whp and 373wtq.  With a full tank of E85, we topped out at 336whp and 379wtq!  As you can see, the majority of the gain occurred by simply getting the car to that E65-ish range and the extra 20 points of ethanol content did not produce an overwhelming difference in power.

Looking for more specifics about our Off The Shelf Maps? Head over to the Map Notes Pages linked below.


These map files are only available to be downloaded from the Maps section of the COBB website.  Download Flex Fuel Off The Shelf Maps HERE.

Custom Tuning Support

Subaru Accesstuner Pro HL has also been updated to support NexGen Flex Fuel hardware.  COBB Protuners can create custom calibrations for emissions compliant vehicles that are utilizing our NexGen Flex Fuel Ethanol Sensor Kit and 5-pin Fuel Pressure Sensor Kit.

Find your preferred COBB Protuner HERE.

64 responses to “Subaru NexGen Flex Fuel”

  1. This new flex fuel kit you have coming out…are there going to be any adapters for the old flex fuel kit so we can use. Or is this a total different setup? You guys said that since the old flex fuel kit plugged into the TGV is why it was not emission compliant, correct?

    Also, are you guys making any redline carbon fiber intakes for the 2008-2014 STIs?

    • While the overall operation is different, we will have an offering that will allow those with our old Flex Fuel kits to upgrade their configuration to the NexGen solution.

      We are not currently working on a Redline intake for 2008-2014 STIs, but it is something we would like to do at some point.

      [email protected]

    • Flex Fuel allows you to have a single calibration that is compatible with any blend of gasoline-ethanol. In an engine’s operation of “suck-squeeze-bang-blow”, a higher ethanol content makes it possible to increase the size of the bang without detrimental results.

      [email protected]

    • We will not be offering a buy-back or “trade-in” program however we will have a lower-cost option available for those who do not need to change their entire configuration in order to use the new solution.

      [email protected]

  2. I need a new turbo upgrade and rub flex fuel on my 2016 STI. When will the new kit be available? ETA?

  3. Will it be available for the 15-21 wrx FA platform?
    I been wanting to go e85 with my 17 wrx but EPA hit Cobb a week after I got it.

  4. Will existing Accesstuner Race customers have access to “Subaru nexgen flex fuel” features?

    Will differential fuel pressure compensation be migrated to a “nexgen” implementation?

  5. My understanding is these NexGen F.F Kits will obviously be CARB EO approved.

    So my question is, what makes the kit?
    Im thinking, in order to properly run F.F at a stage 1-2 level, the kit would need:
    – Down pipe
    – Injectors (1000s?)
    – Fuel pump
    – F.F Hardware
    – MAF and MAP
    – Intake (as an option for those running stage 1 CAN)

    I have a 2011 WRX, and i reverted back to stock after running E85 for years, just to meet CARB requirements. So I, and presumably many like me, will need all these parts once again. So im hoping “the kit” is all inclusive.

    • Hey there! This initial release will be what we call a “49-State” release as we do not yet have an EO from CARB. While we have completed and passed third party emissions testing, we have not yet received an EO from CARB. As far as the kit for your 2011 WRX goes, it is currently TBD. Our focus thus far has been on 2008-2021 STI since we do already have a NexGen Stage 2 Power Package to support the fueling requirements, we plan to develop a similar package for GR WRXs in the near future.

      [email protected]

    • If you’re paying attention to our website or social channels we will definitely make it known when the NexGen Flex Fuel components are available for purchase. Alternatively, signing up for our Subaru mailing list by entering your information HERE will ensure you receive an email from us as well.

      [email protected]

    • The new power package will be supported by an accompanying OTS Map that has gone through and passed third party emissions testing. We are still working towards EO coverage through CARB.

      [email protected]

  6. So those with the old flex fuel kit will be able to trade for the Next Gen flex fuel kit only if you bought directly from Cobb?

    • While we initially planned to offer a trade-in program, we have opted to go a different direction to make things easier for existing customers. Instead of having to purchase the full kit up front for full price and then wait for a credit after shipping your old hardware back, we are just going to sell a lower priced “upgrade package” which only includes the components you would need (module + harness) to upgrade to the NexGen configuration.

      [email protected]

  7. Hey Marshall!
    Just saw the good news on the new FF kits for 2015+!
    What’s the word on the option for 2008 – 2014 without the older kits already in hand?

  8. anyone is going to explain how it works without disabling the CEL. if it still plugs into the TGV or how it works and where it plugs in. Previously CEL needed to be disabled because the ethanol sensor was sending signal over the TGV valve position sensor signal line, how is it all going to work now and how is the signal going to be sent to the ECU/ accessport?

    • The NexGen kits are still injecting data through the TGV Sensor connector but have come up with a proprietary method for that single 0-5v input to transmit data for multiple inputs (Ethanol Content, Fuel Pressure, and TGV Sensor location).

      [email protected]

  9. Hey Marshall, when will the upgrade kits be available and will old tunes still work with the upgrade kit

  10. What is the time frame on getting that carb eo number approved? As this would be awesome in leaving my vehicle as is.

  11. I purchased the old flex kit last year before the update and never got to install or use it, for my 2019 wrx, hoping it won’t just be a paperweight and I can use it or exchange it for when the new one comes out

    • Hey Chris, our offering for the 2015-2021 WRX would likely follow a similar strategy to what is currently available for the STIs. That is, a full kit along with the ability to change only the necessary parts to use the new solution. It is most likely that the only reusable part will be the Ethanol Content Sensor and any connecting fuel lines. The wiring harness/module you have will not be compatible. I’ll have our CSR team reach out and explain your options if you’d like.

      [email protected]

  12. I have a 2018 WRX with the stage 2 NexGen package, will there be a CARB approved flex fuel kit available for purchase? And if so what will the timeframe be? Thanks.

  13. Will this be available for the 2022 WRX?? I’ve heard the fuel pumps can handle full E85 and I can’t wait to try it

    • Not available yet, but we certainly intend to added when able! Some preliminary testing does show that the pump can handle higher ethanol contents, we’ll see how long term durability testing shakes out.

      [email protected]

  14. with the 2018 sti I have the cobb gesi downpipe installed and an intake that is not installed If get the SUBARU STAGE 1+ TO NEXGEN STAGE 2 + FLEX FUEL POWER PACKAGE UPGRADE STI 2015-2021, will I have to put the stock downpipe back on, or can it be tuned with the intake and cobb downpipe?

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