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Frequently Asked Questions

Do I need anything to run E30/E85?

For E30 you do not need to change anything but the tune on the car. However we will not tune an Ecoboost Mustang without an upgraded intercooler. Other vehicles we support intercooler's are OK but can heavily benefit from being upgraded. 

The biggest benefit of E30 is that you can run more spark, that is where most of the power comes from. If you have a stock intercooler the charge air temps reduce spark timing to prevent knock. Though the chances of getting knock on an E30 tune is low we still prefer to make the most out of the tune without any handicaps. For Mustang we recommend SpeedFactory and ETS intercoolers. For the Fiesta we recommend CP-E or MAPerformance, Focus ST Garrett or Steeda, and the Focus RS we recommend ETS only. 

Click the logo above to be taken back to the homepage and select your vehicle to purchase any of these recommended intercoolers.

For straight E85 or any ethanol mixes above E30/40 you will need one of our port injection systems or a high pressure fuel pump (HPFP) and injector upgrade linked below. For the Fiesta ST on stock turbo you can run up to E50 before needing a port injection kit, however anything above E30 is unnecessary on the stock turbo as it will make the same power. If you have an upgraded turbo on your Fiesta ST and want to make more than 300whp on E30 or higher you will need an aux fuel kit or upgraded pump and injectors. 

TunePlus, Inc E85 Port Injection Kit

Pump and Injector Upgrades

The link above contains all information on what is needed to run E85 in your vehicle along with suggested modifications to run in conjunction with the port injection system. 

Mixing E30

First step is to test the E85 percentage at the pump you are going to be using. You can test it with the below:

Once you know the ethanol percentage of the E85 you will need to use our ethanol mix calculator to determine how much of each fuel to put in your car to reach your desired ethanol mix. Please bookmark the page below, it is setup perfectly for mobile for use on the go!

Ethanol Mix Tool!

The calculator is most important when you need to fill up on E30 if you already have E30 in the tank. The Calculator will ask you for the ethanol content in your tank currently. This is because you can’t do the same mix ratio every time or you will run too much ethanol and the car will go lean. 

It will also ask you for percentage of fuel in the tank currently, you can find that by making a gauge on your accessport “Fuel Level Input” and it gives you a percentage of fuel in the tank based on your vehicles tank size (Sizes listed  below). If it says 25% that means you have 25% of (Tank size) gallons of fuel in your tank. 

Always account for the ethanol that is already in your 91 or 93oct. Unless you are in the midwest and your pump specifically states ethanol or alcohol free you have 10% ethanol in your fuel. Make sure you enter that into the calculator as 10% goes a long way. 

If you want to make sure you are mixing ethanol correctly we offer bluetooth ethanol content sensor kits for Ecoboost Mustang, Focus ST, and Focus RS. 

Bluetooth Ethanol Content Gauge Kits

Once you have the mix right and tank filled up you can flash your E30 tune. We suggest driving for 10-15 miles to ensure the E30 makes it to the fuel rail. Your sending unit and lines can hold a lot of fuel, so best to run it for 10-15 miles to be sure. 

Tank Sizes:
  • Focus RS - 13.9 Gallons
  • Ecoboost Mustang - 15.5 Gallons
  • Fiesta ST - 12.4 Gallons


Check Engine Lights

Here is a list of common check engine lights and their cause:

  • P04DB - This mostly comes up when you alter the PCV system with a catch can or breather plate. 
  • P0171 - Common with ethanol tunes or modified intake systems, it gives a false lean condition due to over compensation of the ECU to maintain stoich AFR. 
  • P0141 - Fault in the rear o2 sensor, mostly from aftermarket downpipes
  • P0131 - Fault in the rear o2 sensor, mostly from aftermarket downpipes
  • P0054 - Fault in the rear o2 sensor, mostly from aftermarket downpipes
  • P0135 - Fault in the rear o2 sensor, mostly from aftermarket downpipes
  • P0137 - Fault in the rear o2 sensor, mostly from aftermarket downpipes
  • P0138 - Fault in the rear o2 sensor, mostly from aftermarket downpipes
  • P0420 - Fault in the rear o2 sensor, mostly from aftermarket downpipes
  • P061B - Torque error from the tune not accounting for additional torque
  • P0035 - Bypass valve unplugged, most common with aftermarket BOV
  • U0284 - Grill shutters unplugged, most common with intercooler installs as shutters have to be removed.
  • P0071 - Ambient Air Temperature unplugged, this sensor is usually overlooked when an intercooler is installed. It is located on the lower grill shutter and needs to be removed from the shutters and re-installed 

My Car Smokes After Exhaust Changes

If you get a smoking issue after you installed a downpipe or catback exhaust you need to address your PCV system. The factory PCV doesn't allow for enough crankcase venting and builds pressure and pushes oil past the turbo seals. The solution is to add a catch can and gut the factory PCV valve or run a Radium Crankcase Breather Plate linked below. Both will require a catch can, you cannot gut the factory PCV and run it in the stock configuration as you will pressurize your crankcase system and cause more issues. If you gut your factory PCV Valve you will need a UPR 0-100PSI check valve as well.


Ecoboost Mustang Fuel Sensor / EVAP Solenoid

The Ecoboost Mustang has received updated lowside fuel pressure sensors and EVAP Purge solenoids over the years. No information provided by Ford, just new part numbers and clear updates to the product. These new parts magically fix known issues with the Ecoboost Mustang. 

  • The new lowside fuel pressure sensor cures a High Pressure Fuel problem. When the lowside fuel pressure sensor fails, when you get into load the fuel rail pressure will drop to almost 0. The high pressure fuel pump thinks there is a problem and instead of bypassing it just simply shuts down. 
  • The EVAP purge solenoid update cures issues with the short term fuel trims when under load. When the EVAP purge solenoid fails the short term fuel trims will go to 0 and you will not get any fuel corrections under load (mostly full throttle) and the car can potentially go lean. If you have port injection or methanol injection, or making 400whp+ this can cause catastrophic failure. 
  • Both items can fail without any check engine light, and you would have no way of knowing. It is best to just replace both of them to avoid any issues, they are extremely cheap. 

Lowside Fuel Pressure Sensor Part Number - BU5Z-9F972-B

Evap Purge Solenoid Part Number - FR3Z-9G297-H

To know if you have the updated parts above, they will look like this: