So do most of you just change the stoich value in the tune every time you get gas/E85?

 

I fill up with 50% e85 every time i put fuel in so i know its always the same mixture. 5 gallons of 87 and 5 of e85, or 10 and 10, etc. When i went back to 91 for a road trip i just found the new e85 content after filling up and adjusted stoich accordingly. On the 3rd tank, the alcohol content was negligible.

Have you looked at atomic's excel calculator?

 

Yes, I've seen the spreadsheet. Just wondering if there was a way for the computer to adjust based on ethanol percentage by itself. Looks like I will just have to update the tune when I add E85 to the mix.

 

Only if its a flex fuel truck to being with and has the sensor....not sure how hard it would be to add the sensor and pcm though...

 

Yea it sounds like no one has added the sensor to a non flex fuel truck. I know the newer trucks don't have the sensor. The ethanol content is calculated by algorithms. Do the older style pcm's only use the sensor?

 

There are two types of sensors, and both have their disadvantages. I have looked into it myself. The fuel conductivity sensor in the old trucks is the one that provides the PCM with immediate alcohol content measurement. The problem is they have a high failure rate. The other type isn't really a sensor at all...its just a logic process that monitors long term fuel trims. If the trims are outside a preset margin of error, the PCM interprets it as alcohol in the fuel and richens the mixture accordingly. This method is sort of bullshit though because every time you put more than 3 gallons in the tank, the truck is more or less in limp mode until it determines real alcohol content so lead-footed drivers don't blow their **** up after filling up at an e85 station.

I like the direct measurement, if anything... One of these days I may snag one of those sensors, rip it apart to see what makes it tick, and fix what makes it shitty

 

Here is the part number for the sensor: 12570260. Looks like it can be mounted anywhere that fuel is flowing. The return line might be a good place for it. I wonder where you would wire it into the pcm so it functions properly..?

 

I have one of those sensors Jake. I wanted to put it on my truck so I can run any mix of E85 and not worry about it, but there is no COS that will work with the 512 PCM that has the alcohol tables in it...

I've even though about putting a Mega Squirt MS3 on my truck just for fueling like Parish did. Then I could just have WB close loop fueling and would be right all the time in or out of boost.

 

What extra tables are in the operating system for alcohol. I noticed mine has an open loop alcohol table but that is the only one I saw.

 

stoich ratio vs alcohol content