Good thread, I was going to make one of these eventually.
I'm personally going to do separate E85 and 91 tunes, so I bought a cheap second ECU to put the other tune on and keep in the car for when I need to switch to pump gas on the fly (I bought it to tide me over until someone figures out multiple map switching on 1 ECU). But after that I bought a cheap Acer Aspire One netbook that I'm going to always keep in the car with flashing software and my different files. So I'll be able to flash files whenever instead of physically swapping ECU's.
Since I've got a laptop always in the car to flash whichever file, I will likely tweak the E85 tune when the fuel changes for the first time, so then I'll have different files for E70 winter, E85 summer, and whenever else.
I'm putting an ethanol content analyzer in my car and will likely check the content after almost every fillup. I was checking out the ECA from Zeitronix, but it seemed pretty expensive for just a gauge (you still had to go get the actual sensor from a junkyard.) So what I decided to do instead is buy this small digital o-scope to keep in the glovebox, with which I can accomplish the same thing as the Zeitronix ECA (and then I can use the o-scope for other stuff that I need to when I'm not checking the eth cont
). The sensors in the OEM flex fuel vehicles indicate ethanol content and fuel temperature by sending a wave with a certain frequency and pulse width. The frequency indicates ethanol percentage, such that 50hz=0% ethanol, 150hz=100% Ethanol, and +1hz=+1% eth. The pulse width determines fuel temp such that 1 millisecond = -40*F and 5 milliseconds = 257*F. I'll print out calibration charts like this and keep them in the glovebox with the o-scope, to check the stats after filling up.
-Here's a list of the cars to pull the OEM sensors from (new they're $300+, so act like it's just some small sensor):
http://www.zeitronix.com/Products/ECA/ECA.shtml-Here's the o-scope I bought (I've heard of people going with a cheap $30 DMM from Sears as well):
http://www.seeedstudio.com/depot/dso-quad-4-channel-digital-storage-oscilloscope-p-736.html
Just some insight into how much the ECU does and doesn't adapt, I used to put ~3-3.5 ga of E85 per tank together with my 91 oct, to raise the octane a little bit since I had a tune for 93oct, but only 91 gas available. I eventually tried to add similar amounts to my stage 1+ B6 1.8t A4, but I because the last time I did it (about 3ga E85 and 16 ga total) I tripped a lean condition run code. I didn't want to risk damaging the engine, but the ECU can definitely only adapt so much.
Logged and increased timing based on FATS. Go by FATS and MBT instead of knock or CFs.
So you don't worry about being knock limited at all when tuning with E85, eh? Knock and CF's are still good indicators to make sure the tune is safe though, right? (E85 doesn't affect the knock sensors ability to detect actual knock or anything like that, right?) I'm new-ish to MBT tuning as well, but is MBT boost independent then?
Say one was knock limited on a pump gas tune, then goes E85. Turns up the injectors and finds MBT. Checks knock/CF's and they're still in check. Assuming the turbos still have some efficiency to go, then would you up the boost (while keeping lambda in check) until it's knock limited again (assuming that the knock limit comes before the turbo leaves its efficiency range)?
