Since a E85 station is pretty close to me know I was thinking of possibly switch to E85.. I have been doing some research and reading various threads and I know I can change my tune to run E85 but I would like to see if I can get the computer to do it like the flex fuel vehicles do without the use of the Fuel Composition Sensor..

So looking at the Pin Out diagram I noticed Pin #56 on the C1 connector says "Fuel Composition Sensor"... So I am assuming that pin is used to determine the amount of E85 in the gas.... Looking in my tune it has a table that determines the % of E85 to adjust the tune accordingly. So I think the pin's input is a voltage range rather than just a Hi/lo or Ground... I saw another pinout diagram that said that pin is also used for Fuel Temperature. So all that leads me to believe that it is a 0-5v input... I can make a circuit easy enough to simulate the 0-5v or 0-12v range, and EFI Live has a PID (GM.E85PCT) that measures the % of E85 in the gas, I am assuming it comes from Pin #56. So with all that said, I think the switch can be made... I bet it will require me to do a full flash with a E85 tune then flash in my 4.8 specific stuff....

What do yall think, think it can be done?

 

I like your thinking. a few SSS guys are playing with E85.

 

Well after a little bit more research the Fuel Composition Sensor outputs a square wave that goes for 0 to 5v... The frequency of the wave form determines the amount of ethanol in the fuel...

50 Hz is 0% Ethanol
150 Hz is 100% Ethanol

So in order to get the proper signal to the PCM a wave form generator would have to be used... I found a assemebled circuit UK305 that is adjustable and can simulate the output....

However all this wont do me any good, the gas station I thought sold E85 does not... The nearest place is like 30 miles away, so E85 will have to wait for awhile...

 

I wouldn't bother with the sensor. Just run it and have a couple of tunes built for ratios less than 85%. Mine runs fine and I've had to mix gas in with my E85 a few times.

Just change your injector size by 22-25% and it will run nicely. Then you can tweak it from there.

 

bump anymore use of the PCM or addition of sensors to help this work easier???