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Series: 2015+ Subaru WRX Modification (Pt.9 - Alternative Fuels)

March 29, 2021

2015+ Subaru WRX Modification (Pt.9 - Alternative Fuels)

Series: 2015+ Subaru WRX Modification (Pt.9)

     Hello and welcome to my Op-Ed on the 2015+ Subaru WRX! This is part 9 of a 10 part series that plans to encompass all of the information you will need to make informed decisions regarding the best upgrade path for your vehicle.

     This week, I will be giving an in-depth overview of Alternative Fuels. This overview will consider the benefits and drawbacks of certain alternative fuels as well as how to account for them during the calibration process.


     The statements made in the article below are subjective and based on my knowledge and experience gained from working with the VA WRX platform.  Please refer to your preferred tuner, or a trusted vendor, for recommendations on your specific set up.


     This Op-Ed is intended to help the user better understand how certain modifications affect the engine and performance, what tuning changes are necessary to account for these modifications, and what brand(s) I recommend for each modification category. This is NOT intended to be a tuning guide. I am NOT an expert in ANY category that will be discussed.


Modifications and Preferred Brands


     Methanol injection is the process through which an atomized mixture of water and methanol fuel is injected into your engine’s intake tract. This offers multiple benefits including, but not limited to: increasing octane, reducing EGT (Exhaust Gas Temperature), and suppressing detonation.

     Methanol is typically introduced immediately before the throttle body by means of an injector. The injector is controlled via a control unit that has a built-in pressure sensor and multiple controls. The user typically has control over what parameters must be met in order for the injector to activate and deactivate. On most systems, the amount of injected methanol blend is controlled by a jet device that goes in the injector nozzle, and then into the intake system.

     While the benefits of methanol injection are substantial, I will not be discussing methanol further because my experience with it is extremely limited. For additional questions about methanol injection, please contact your preferred tuner.

15+ WRX Water / Meth Injection 



     Ethanol is derived from corn whereas gasoline is derived from petroleum. In fact, ethanol was originally mixed with gasoline in an effort to make the mixture non-potable! Ethanol contains less energy per unit than gasoline does. This results in a reduction in fuel economy. It also doesn't provide the same lubricating qualities that gasoline does which results in excess wear on fuel system components such as the high and low pressure fuel pumps. However, these downsides are heavily outweighed by the many upsides of running ethanol.

     Octane Boost: Ethanol provides a sufficient boost in octane when mixed with gasoline. The process of mixing ethanol and gasoline together is called blending. Typically, pump gasoline sits somewhere between 0% and 10% ethanol content. This solely depends on the provider and distributor. Pump E85 typically sits between 51% and 83% ethanol content. This depends on the provider, distributor, geography, and season. Depending on specific content and mixing ratios, one can theoretically achieve any ethanol content between 0% and 83% depending on the factors mentioned above. As this percentage increases, so strengthens the pros and cons of ethanol in your vehicle. It is also worthwhile to mention that purer forms of ethanol (>83%) can be sourced as well although it is typically not sold at public fuel stations.

     Combustion Temperature: Because ethanol has a lower BTU (British Thermal Units) value than gasoline, it actually burns slightly colder than gasoline does. This adds more knock resistance and fortifies the benefits of something like a larger intercooler. For this reason, ethanol is a very enticing fuel for any vehicle that sees heavy abuse, such as a race car.

     Flex Fuel: Another benefit of ethanol is the ability to program a flex fuel setup on your vehicle. Flex fuel is the ECU’s ability to determine and adjust a set of parameters based on a measured ethanol content. It’s essentially an infinitely changing calibration that will adapt to fit whatever ethanol content you choose to throw at it (within a predetermined range). Needless to say, flex fuel is the most common application for ethanol on the FA20DIT and that’s mostly down to the versatility and reliability of the setup.

     Tuning: Due to the energy deficit per unit of ethanol vs gasoline, the stoichiometric ratio maintains an inverse relationship with ethanol saturation. As a result, more fuel volume is required to achieve the same combustion. For most cases, this is achieved via injector scaling. For the same reason, cranking and enrichment tables must be augmented to suit. With ethanol, the extra knock protection allows a tuner to optimize every part of the combustion process. Fueling can be leaned out. Ignition can be advanced. Boost can be increased. All of this, and more, comes together to increase both power potential and reliability.


     Tune in next week (04-05-2021 @ 12:00 EST) where I will be giving an in-depth overview of Ethanol Sensors and Low / High Pressure Fuel Pumps. This overview will consider the purpose of each component, how to account for it in a calibration file, as well as what specific brands I recommend.