Switching to E85 and back
 

Planning to re-map my ecu (probably Ecutek or Openflash) and have two maps, one for 93 that's readily available and one for E85 that's 1/2 hour drive away. I plan to run E85 occasionally, and 93 the rest of the time - what's the procedure for switching to E85 and back?

1) I can run the tank low, but it's likely to have a gallon or two still left in the tank, this ok for most out-of-the-box E85 maps out there?

2) After filling up with E85 when do I actually change the map - isn't there gas still left in the fuel lines that I need to run out first? And same with switching back to 93 octane gasoline - do I have to run the E85 out of the fuel lines first before switching maps? I imagine running E85 on a 93 map, or vice versa is not a good thing at all (e85 map with 93 will run uber rich with way too much timing, and 93 map with E85 will run ultra lean with not enough timing, right?).

Thanks

I wait until the fuel night is on and generally go another 40 miles. You want to have less than 10% remaining.

I have flex fuel. I usually watch the fuel remaining value via ecutek but thats not even good enough. It will show 0% remaining. If I fuel up there I usually still have 1.1 gallons remaining and can get around e79.

Keep a gas can in the trunk with the fuel you are seitching to.

When you get even lower than that the the new fuel gets sucked into the enfine pretty quickly after starting up the car.

You wont be doing any damage driving onvthe wrong fuel for short periods. Hell I had to drive over 100 miles on pump gas with an e85 tune when a laptop died. I ran rich but got home.

Sent from a Motorola DynaTAC 8000X

Ok thanks - ideally I should do what you've done and go flex fuel, but it's kind of a big total investment for me at this point, especially when I'm mostly 93 and will run E85 once in a blue moon for 'fun'. The angel on my one shoulder keeps telling me to not fool with it and just run 93, but the devil on the other shoulder keeps reminding me how massively awesome E85 tunes are on this car!

You need to add a caviate about driving with pump gas on an E85 MAP... DO NOT GO WOT.. a properly tuned E85 map will have WAY more timing under full load than pump gas.

Generally as Yruyur said you want to run each fuel down as low as you safely can before switching either way.

It would be good to start by mapping out how much fuel you have left wit the needle at a given position and also take into account actual mileage on each fuel type (E85 you won't know until you get a few tanks). This way you know what your mix will be when you fill up with either fuel.

For example, I just switched back to 93 for some testing. I ran the tank down till the light came on, then i reset the odo and the avg mpg and drove another 20 miles. I already had 6 gallons of 89 octane in the trunk just in case i ran out and my laptop in the seat. I knew i would have between 1.2 and 2.2 gallons when i got to the house. 2 gallons E85 + 6 gallons E0 89 = 8 gallons E20 93 octane.

Got home, added 6 gallons 89, started the car on the E85 map and started the logger and watched the fuel trims while slowly reving the engine. It was taking a VERY long time to get the E85 pushed through and the 89 mixed in, once the trims hit +15% i shut it down and flashed in my 93 map. Let it idle for a few minutes then got impatient and drove it around the block. That got the fuel pushed through.

The next AM i drove straight to the pump and put in 6.1 gallons of E10 93, topping off the tank. It turns out I had more like 1.2 gallons E85 when i addded the 89. I would not have known that without filling up the rest of the way.

So, the key is logging and being prepared. It will take a few minutes to push the remaining fuel through the lines, but it goes MUCH faster if you fill the tank to the top with the new fuel (crosses over the saddle and mixes quicker). You want to crank up on the old fuel map first then switch maps after the trims get about 1/2 way there.

E85 to pump trims will go - as pump gets mixed in
pump to E85 trims will go + as E85 gets mixed in.

Here is the mix calc i use:
http://www.intercepteft.com/calc.html

Great detail.

Sent from a Motorola DynaTAC 8000X

Always extremely helpful posts mad_sb. I'd been using a similar routine, but nice to get confirmation from the pros. Thanks again :)

Thanks man, but I'm far from a pro, this is the first E85 tune i have done :)

Anyway, just wanted to mention, I only blended with 89 octane to get my octane down to 93 as quickly as possible since i was doing some basemap testing and won't be on pump gas long enough to run through multiple tanks.

Wooot. Let us know how the ethanol tune goes for ya. I still say you need to start a groupbuy to get yourself brzedit pro and start selling tunes to the forum members. ;)

Haven't been on here for awhile good to see it's still going strong. Everyone gets in different habits that work. Personally I run a Visconti E70 tune full time and have gotten the best performance from that. The station I use typically has 80% ethanol E85. When I switch from pumpgas I run it down to where the gas gauge is just below E then fill up with the E85 (E80). Flash to E70 tune and voila. After that I refill with a 6 gallon E85 to 1 gallon pumpgas ratio (gas is E10 there). Just baby bottle test the fuel periodically. 100ml water + 100ml of fuel and ml of separation is the % gas. I get way better performance this way than running on an E85 tune personally. Probably because I have to watch the ethanol content more closely. Switching back to pumpgas just run it below E and refill / flash. I'm also ready for winter mix this way and don't have to worry about cold starts in cooler weather. My .02. If you have a plan you'll be good so long as you're aware of how much fuel is really left when you hit E.