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Flex Fuel E-Tune (Open Source) – 2006-2014 WRX / 2004-2020 STI

Flex Fuel E-Tune (Open Source) – 2006-2014 WRX / 2004-2020 STI


Currently we only have flex fuel maps for the following:


2006, 2007, 2009


2005, 2008, 2009, 2010, 2015, 2016, 2017, 2018

Please contact us if you have a different model and are looking for flex fuel tune.

-Wideband AFR logging REQUIRED – Can be wired to ECU or Serial Logging via Romraider

Once purchased we will send you a confirmation email with a link to our online pre-tune form. With the pre-tune form, we make sure you have all the correct modifications to meet your power goals.

Once filled out we will email you to get the E-Tuning process started.

All E-Tunes have a 6 month timeline to be completed. Most E-Tunes take less then a month if you are actively sending new logs. 


By purchasing this product, you acknowledge that this is a digital file sent via email, so there are no refunds and no warranties. You have also read How E-Tunes Work and have gone over the Pre-Tune Checklist.


We currently don’t have a Flex Fuel option for your make and model.

Please contact us at to know when it will be available.


Check out our Mods Guide to see dyno graphs of power outputs and for a good mod path for future modifications.

Pump Gas Typical Gains (Stock Turbo)

  • 280+ hp to the wheels!
  • +30 hp (16%) increase in horsepower over stock
  • +60 ft/lbs (29%) increase in torque over stock

Ethanol (E85) Typical Gains (Stock Turbo)

  • 370+ hp to the wheels!
  • +80 hp (40%) increase in horsepower over stock
  • +120 ft/lbs (60%) increase in torque over stock

*Noe for 2006-2008 WRX – Quoted power increases are only when running an STI turbo on the 2006-2007 WRX or a VF25 on the 2008 WRX 

Open Source E-Tuning

With Open Source E-Tuning, more is required from the customer than E-Tuning with an Accessport. You MUST have a laptop and be able to install the Open Source programs Romraider – for logging and ECU Flash – for downloading and flashing tunes to your vehicle’s ECU. We will provide all the download links and detailed instructions on how to download the programs. Romraider is a free open source program created by enthusiasts like you. The installation process of Romraider is more involved than commercial programs but nothing most people can’t accomplish.

You will also need a wideband AFR gauge like AEM or Innovate. The gauge will need to be wired to the ECU or use a serial adapter to log with Romraider.

Features included for most years:

  • 2008+ Boost By Gear: All MT tunes have boost by gear. This helps your car hit close to boost target in all gears
  • Smoother boost for more linear power delivery
  • 2008+ High Gear Over-Boost ProtectionWe employ over-boost protection for 5th & 6th gear in 6speeds and 4th & 5th gear in 5speed, to limit boost below defined rpms. An example is if someone goes WOT in too high a gear at too low an rpm, boost is limited to wastegate pressure to keep engine loads low and reduce the risk of engine damage.
  • Launch control / Flat Foot Shift: Available for most years
  • Speed Density: Available for some years

If you have any questions about E-Tuning you can call us at 763-316-5882 or email us at


Additional Information


2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014



Upgraded Turbo

No, I have a stock turbo, Yes, it is upgraded (+$100)

Speed Density

Yes Please (+$100), Not Needed, Not Currently Available, Please contact us for options

Pre Tune Checklist

Tuning DOES NOT fix mechanical issues or misfires. Tuning is for vehicles that are already in good running condition.  Tuning is for making aftermarket parts work properly together.


Fuel Related Pre Tune Checks

  • Do you have the fuel octane you want to be tuned on in your tank? – It is critical you have the fuel you want to be tuned on in your fuel tank when you come in for the tune. We can only tune your car for the fuel that is in the fuel tank. If you tune on 93 octane you will make more hp but you can damage your engine if you boost with 91 or 92 octane in your vehicle. If you want to be able to run 91, 92, or 93 then you will want to tune your vehicle with 91 octane in it.
  • Do you have nonoxygenated 91, a.k.a. no ethanol 91, ethanol-free 91 in your fuel tank? – We do NOT  recommend running 91 non oxy or non ethanol fuel (see images below for examples). We have found turbocharged Subaru’s do not like this fuel and it acts like a much lower octane in real life testing. We will tune your car on that fuel and you will make substantially less hp. If you decide to come back with a better fuel you will have to pay for a tune adjustment (e-tune hourly rate). If you only have access to 91 non oxy, we have found an aftermarket intercooler can help keep the power where it’s supposed to be.
    • We have found that most Kwik trips in Minnesota have nonoxygenated 91 and the pump is not always labeled non oxy, so we recommend staying away from them for pump gas.
  • Is your MAF (mass air flow) sensor dirty?– We recommend cleaning your MAF with MAF cleaner before your tune. If we tune your car with a dirty or bad MAF, if you ever decide to clean or replace it your tune will likely be off and you will need a new tune (we DO NOT recommend using aftermarket MAF sensors, even if it’s the same brand as the OEM they can read differently than stock and typically don’t last as long. Always buy OEM from the dealer)
  • Does your front O2 sensor operate correctly?– If your front O2 sensor is not working we can NOT tune your car. (we DO NOT recommend using aftermarket O2 sensors, even if it’s the same brand as the OEM they can read differently than stock and typically don’t last as long. Always buy OEM from the dealer)
  • Check or replace your fuel filter
  • Check/set fuel pressure. (If you installed an aftermarket adjustable fuel pressure regulator you need to set it. All aftermarket fuel injectors are flow rated at 43.5psi. That is the recommended base pressure for you to use. Always set base pressure with a warm engine and the vacuum line disconnected from the fpr and plugged.)
    • Stock Fuel Pressure from the Manufacture
    • All turbo EJ Subarus- 41-46psi


non oxy vs 91

Boost Related Pre Tune Checks

  • Verify no boost/vacuum leaks. If you recently installed a front mount intercooler / piping or had your engine apart a boost/vacuum leak test is a must!
  • Clean or replace your air filter
  • If tuning 02-14 WRX/04-07 STI models for over 22 PSI an aftermarket MAP (manifold absolute pressure) sensor is required
  • If tuning 08-2021 STI models for over 26 PSI an aftermarket MAP (manifold absolute pressure) sensor is required

Engine Mechanical Related Pre Tune Checks

  • Perform a compression test– knowing the health of your engine before the dyno tune is critical to make sure you get the most out of your tune. Compression should be within 10% on all cylinders.
  • How many miles are on your spark plugs? If you don’t know the history of your spark plugs please replace them beforehand. If your car misfires from a bad or improperly gapped spark plug on the dyno we can not complete the tune until that issue is resolved
  • We CANNOT tune with misfires
  • Do you have any oil, coolant, or transmission fluid leaks.– All leaks should be addressed before your e-tune. 
  • When is the last time you changed your engine oil?–  We recommend having fresh engine oil to help prevent engine failure at higher RPMs. Mobil 1 and Royal Purple are NOT recommended in turbo Subaru engines.
    • For the EJ engines, we recommend Rotell T6 5w40, Motul 8100 X-cess 5w40, Motul 6100 Synergie 10w40 (good for E85), or Motul 300v 5w40, 15w50.
  • Does your car overheat at idle or under load?– Your cooling system should be properly burped and be able to keep your car form overheating at idle or when driving.
  • Do you have any exhaust leaks?– exhaust leaks can cause the AFR sensors to read inaccurate and potentially cause the tune to be incorrect.
  • Do you have any check engine lights on?– Your car should NOT have any check engine lights on when you come in for the tune.

Vehicle General Maintenance and readiness to strap on the Dyno Pre Tune Checks

  • Are your tires properly inflated?– Make sure tires are fully inflated to the correct pressure (30-40psi recommend) 
  • Does your car drive strait down the road?– Your car should have a proper wheel alignment.
  • Is your clutch up to the task of holding more power?– Make sure your clutch is not slipping and able to handle the torque for the upgraded mods
  • Does your battery and charging system operate correctly?If the battery dies while flashing a tune on the car it can brick the ECU, leaving you with a car that will not run. If your car has to be jumped every time to start it needs a new battery in order to be tuned.
  • How old are your Transmission, Rear Diff, and Transfer Case(where applicable) fluids?– make sure these fluids are fresh and full . 


How E-Tunes Work

What is a E-Tune

The short answer is we provide you a tune via email. The long answer includes you getting to have some fun in your car. Have you ever wondered how E-Tunes work? The following information will provide you will all the ins and outs of how E-Tunes work. With this knowledge, you can confidently purchase an E-tune and start getting more smiles per gallon. Once you purchase an E-Tune we will email you your first revision along with detailed instructions to complete the E-Tune. The instructions include everything from loading the tune to your Accessport to performing data logs. All you have to do is send us data logs, we then review them and send you a new revision. Rinse and repeat until the tune is complete.

E-Tuning is a great way to get a custom tune without getting on a dyno. A dyno simulates road load. Since it does that we can accomplish a tune without putting your car on the dyno with the logs you send us. E-Tuning does not replace dyno tuning and is not a less expensive option than dyno tuning. A dyno tune will always get you the most power and the best driving tune. With that said an E-Tune will still get you a well-performing and reliable tune. If you don’t live near a dyno facility an E-Tune is a great choice.


Running a OTS map can be a great option for some people, the only downfall is they require spefic parts. If you have/want to run different brand parts or once you are modified beyond their staged tune specifications you need a custom tune. Since all of our E-Tunes are custom to each car, we can get you a smooth running and well performing tune for your exact mods. We have years of experience dyno tuning the 2002-2014 WRX / 2004-2021 STI and know exactly what to do when tuning to give you the best driving car.

How E-Tunes Work/Typical Work Flow 

  • Purchase your E-Tune
  • Fill out the online form, received with E-Tune purchase, with mods list and we will send you the first revision.
  • Flash tune revision/perform logs
  • Email the logs to
  • We will review the logs, typically within a few hours up to 48 hours, make the needed changes to the tune and send a new revision
  • Send more logs and receive more revisions. This usually takes 5-10 revisions for a single fuel tune, more for flex fuel.
  • Once the tune is complete, we will send you a virtual dyno graph that gives you approximate horsepower and torque figures

What is needed from you to complete an E-Tune:

  • Working computer/laptop
  • Good internet connection to email logs and receive revisions
  • Good running car with no mechanical issues
  • A good flat section of road for the WOT (wide open throttle) portion of the tune. This is best so all the pulls have similar loads on the engine

Things to understand about E-Tuning

Tuning DOES NOT fix mechanical issues or misfires. Tuning is designed for vehicles that are already in good running condition and designed to make aftermarket parts work properly together. If you are booking a tune because your car is running poorly that will need to be addressed before we can start the tuning process. Check out our Pre-Tune Checklist for more information.

If we run into mechanical issues while tuning, the tuning will be paused until mechanical issues are fixed. We tune these cars all day on the dyno and know when parts are performing as expected. 9 times out of 10 when we have issues, it’s a mechanical issue and not related to the tune at all. If after a few revisions the car isn’t responding as it should it will be up to you to either diagnose and repair the problem or bring the car to a reputable shop that knows how to diagnose and fix issues on these cars. We can only help you so far over the internet.

E-Tuning revisions and log reviews are done Mon-Fri 8:00 am-4:00 pm (CST). E-Tuning is not available on the weekends. You are welcome to perform your logs in the evenings or weekends and email them to us. We will review them as soon as possible during our open hours and send new revisions. Depending on the time of year and how busy we are, you may receive your tune revisions in a few hours up to 48 hours after the data logs are sent.

Emissions Compliance Up-Dates:

Times are changing. To keep the aftermarket performance industry alive and following Cobb’s “Project Green Speed”, we can not disable any check engine lights while Tuning. That means we cant tune your car with an Accessport if you have Air Pump or  TGV Deletes. If you have any questions or are unsure if we can tune your car, please contact us at

We CAN still tune E85, Upgraded Turbos, Fuel Injectors, Fuel Pumps, Intercoolers and more. These updates really only remove the ability to turn off check engine lights and flex fuel. We already off a new version of flex fuel, that works with the latest Cobb Green Speed updates, for the 2015+ WRX and more models are soon to follow! Check our Blog for the latest updates.

Cobb Tuning Project Green Speed Updates.

Project Green Speed 3/31/2021

Project Green Speed update 1/31/2022

Project Green Speed update 3/16/2022

Project Green Speed update 4/18/2022 – Removal of Flex Fuel & DTC suppression

Project Green Speed FAQ for 4/18/2022 update



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