To get this started next year I'll be a senior in Mechanical engineering. This year as a junior I'm helping the seniors take a 2007 yamaha Phazer snowmobile (4 stroke 500cc twin) and have it run completely off MegaSquirt. Next years project(aka mine) will be to make the sled be able to run off 87oct-93oct and E10 and E85. I was wondering if any one knows how GM or any other manufacturer senses E85 vs regular dino fuel on their flex fuel motors. The differences with 87-93 is just changing the timing tables via knock sensors. But with E85 you now need to flow a hole heck of a lot more fuel as well as change the timing. Any ideas would be awesome, I'm just trying to get a jump start on next school year.

Thanks

 

Here are some things to read on E85 tuning.
http://www.hptuners.com/forum/showth...&highlight=e85
http://www.hptuners.com/forum/showth...&highlight=e85
https://ls1tech.com/forums/showthread.php?t=378268

 

There are basicly two different strategies one can use.

One is with a fuel composition sensor.(extremly expensive) This concept is used on GM trucks (and I am sure others) 2002 to 2005. The sensor reports the ethanol content of the fuel in real time to the ECU. The ECU responds by adjusting the stoich to what ever value is correct for the actual ethanol content of the fuel.

The other way of doing it, is by software only.
The ecu monitors the fuel guage input, so it knows when fuel has been added.
When fuel has been added, the ecu is in "learn" mode when reading the fuel trims.
If the fuel trim gets pulled up after a refuel, the ecu adjust the stoich to a ritcher setting neccecary for ethanol blended fuels.

Example: running pure gas, stoich is 14,68.
Refill with half tank of E85. (100l tank half empty)
The fueltrims will then start adding fuel to achive stoich combustion.
The ECU knowing that we just refueled, will set the stoich to match the ethanol content in the fuel, and therby pulling down the fuel trims to close to 0%.
In this case the ecu will go from 14.68 (gas setting) to aprox 12,2 to get the correct stoich for 42% ethanol.
Needless to say, closed loop is a must to get this to work.

The software only concept is used by Saab and also on GM trucks 2006 on.

Hope this helps out as a starter.

Br//

 

Thanks for the responses so far. I'll look into more tuning and how Megasquirt II lets me detect the ethanol. I was worried when I posted this I wouldn't get technical responses, but these are exactly they type I wanted, keep the ideas coming.

Thanks!