What Is An E85 Tune?

January 02, 2024
What Is An E85 Tune?

An "E85 tune" refers to a process of adjusting an engine computer’s parameters to optimally run on E85 fuel, which is a blend of 85% ethanol and 15% gasoline. The high ethanol content in E85 has a higher octane rating than regular gasoline, which allows for more aggressive ignition timing and increased boost levels in forced induction engine while preventing damaging knock. E85 inherently makes more power than gasoline because of its faster burn rate, higher expansion rate and faster flame front.  The higher burn rate requires a higher volume of fuel to enter the combustion chamber on each injection cycle. Therefore, an E85 tune involves re-calibrating the engine control unit to increase fuel injector flow rates to ensure proper combustion. This tuning has historically been complex and carried out by professionals to avoid potential engine damage, until now.  E85 tunes are ideal for race grade E85 fuel, which is always 85% ethanol, or close to it.  However, an E85 tune can be dangerous when using pump E85, which varies in content from 51-83% ethanol, and can change from day-to-day, even at the same fuel pump.  When using pump E85, or when the car will be switched between gasoline and E85, the real time Proflex Commander fuel system is much safer for the engine and will produce more horsepower than an E85 tune.


E85 tunes vs the ProFlex Commander flex fuel system

The Proflex Commander takes care of the following needs required to run E85 in a modern Ford Mustang:

  1. Flex Fuel Sensor. Referencing: This fuel content sensor is crucial for safely running E85. It measures the ethanol content of the fuel and sends this information to the Commander digital injector control unit (ECU). This ensures very precise fuel delivery of all fuel blends so the engine runs efficiently regardless of the ethanol content in the fuel.  An E85 tune does not adjust for changes in the fuel and does not require a sensor, however the lack of adjustment is dangerous for running pump grade E85.  

  2. Tuning: The ProFlex Commander maximizes gains on E85 and is compatible with stock or pump gas tunes.  Unlike and E85 tune, the Commander system will make significantly more power with no changes to the existing tune.  Tuning changes can be made, if desired, with the Commander installed.  It automatically adjusts to changes in the tune in about 30 milliseconds.

  3. Cold Start Enrichment: Ethanol fuels like E85 have a higher evaporation temperature than gasoline, which can make cold starts more difficult. Therefore, the ECU must be programmed to provide a richer fuel mixture during cold starts when running on E85.  The ProFlex Commander features our exclusive ColdStart software, which changes injector behavior in cold temperatures and reduces hard starting that is typical of E85 tunes.

  4. Real Time Adjustment: An E85 fixed map tune is what is called a, “dumb tune.”  It is only appropriate for 85% ethanol content fuels.  This prevents the use of variable content pump E85 or gasoline.  The ProFlex Commander adjusts in real time to changes in fuel content and allows the use of E85 race fuel, E85 pump fuel or gasoline.  The system automatically adjust in real time and has zero latency.


Components of the Fuel System

All Modern Mustangs have fuel system components that are fully compatible with E85.  However, some have factory injectors that are not large enough to deliver the increased fuel volumes required by E85.  In particular, the Fox 5.0 and the 4.6 Mod Motor cars require an injector upgrade to safely run E85.  Factory fuel pumps and lines on all unmodified Fox and newer cars are fine with full E85.

When adding bolt-ons, power adders and forced induction upgrades to fuel injectors and pumps is often required.  The key is to make certain enough fuel can be delivered to keep the engine from going lean on high ethanol content fuels.


E85 Tuning

It is possible for owners of newer Mustangs to successfully convert their vehicles to run on e85 fuel with an old school E85 tune and a proper understanding of how E85 management works.  For those who wish to run only race grade E85 to the exclusion of pump E85 or gasoline, and E85 tune is a great option.  For those who want maximum gains and engine safety, installing the Proflex Commander provides fuel cost savings, increased horsepower, cooler operating temperatures, cleaner-burning fuel and improved engine longevity.  The Commander’s compatibility with pump gas tunes makes it a great option for those who want to have flex fuel capabilities with the freedom to make mild or full build tuning upgrades and modifications.