Just started reading about them, and was wondering what was changed to when ethanol was detected. Also wondering about the signal that is outputted from the sensor that the PCM reads.

 

There are several tables that are changed, but the one that has the most influence on the tune is the stoich value. Here is some info on the sensor:

The FCS uses a microprocessor inside the sensor to measure the ethanol percentage and fuel temp, and change an output signal accordingly. The electrical characteristic of the FCS signal is a square-wave digital signal. The signal is both variable frequency and variable pulse width. The frequency of the signal indicates the ethanol percentage, and the pulse width indicates the fuel temperature. The PCM provides an internal pull-up to five volts on the signal circuit, and the FCS pulls the 5 volts to ground in pulses. The output frequency is linear to the percentage of ethanol content in the fuel. The normal range of operating frequency is between 50 and 150 Hertz , with 50 Hertz representing 0 percent ethanol, and 150 Hertz representing 100 percent ethanol. The normal pulse width range of the digital pulses is between 1 and 5 milliseconds , with 1 millisecond representing -40°C (-40°F) , and 5 milliseconds representing 125°C (257°F)

 

can i ask a silly question.. what car and do you have a copy of the tune file for a 411 that runs flex fuel?

 

Wow, I was hoping for a simpler signal.