Map Switching With EcuTek

Reading Short and Long Term Fuel Trims with Map Switching to determine Ethanol content 

Map 1 - PUMP GAS(E10)

Map 2 - E25 (6% More Fuel) 

Map 3 - E50 (20% More Fuel) 

(E85 requires 43% more fuel than pump gas and is damaging to the wrx fuel system as it was not designed to use e85, you are likely to see mechanical failures of the fuel system when using higher than E50) 

 You will be reading a combination of short and long term fuel trims at idle. For example, if short term fuel trims read +2% and long term fuel trims read -1% you have a total of +1% fuel added. With a STFT of -5 and a LTFT of +5 the is equal to 0. The idea is to have Total fuel trims at 0 at idle for each map and mixture. This means you are at the exact content. 

 When adding Ethanol to your tank, you must use the fuel in your fuel lines before switch maps, due to the wrx fuel system design, once fuel is pressurized in the lines it does not return to the tank, so you must burn the pump gas before you change maps.  

When you add ethanol, you will bring up short and long term fuel trims in data longing, start the car, and drive away from the station. When you see the combined fuel trims adding +5% at idle it’s time to change to Map 2 for E25. If you have added E50 to the fuel tank then when you see combined fuel trims adding +15 to +20% at idle it is now time to change to Map 3.  

E25 requires 5% more fuel than pump gas 

    E50 requires 20% more fuel h

an pump gas

If you are on map 2 with pump gas you’ll see -5 to -10% fuel correction at idle, if you are on the pump gas Map 1 and have E25 in the tank, you will see +5 to 10% fuel trim corrections at idle, if your on e50 in pump map, you’ll see +20% at idle and if your on map 3 for e50 and have pump gas you will see -20 % fuel trims.

 Accidentally filled with E85

 If you are on Map 3 and you see fuel trims adding +20% or higher you have added E85 to your tank. You must drive soft until you can add pump gas, even 1 gallon at a time. If you are in Map 3 and still are reading +5 to +10% at idle then you have a higher ethanol content than e50. Add pump gas 1 gallon at a time until fuel trims are near 0 at idle.

  WRONG MIXTURE EXAMPLES

 If you see Total fuel trims -10% at idle on Map 3 this would indicate you have a fuel mixture of E30

 If you see Total fuel trims -5% at idle on Map 3 this would indicate you have a fuel mixture of E40

 If you see Total fuel trims +5% at idle on Map 3 this would indicate you have a fuel mixture of E60

 If you see Total fuel trims +10% at idle on Map 3 this would indicate you have a fuel mixture of E70

If you see Total fuel trims +15% at idle on Map 3 this would indicate you have a fuel mixture of E75 to E80