OK so I'm thinking of making the switch, but I have a couple questions about real world scenarios.

Let's say I'm out and about and I'm low on gas, but not near a station. Do I just fill up with 93 and switch maps to the 93 map?

Will the E85 left in the tank mess up this map & performance?

What do I do when I get E85 again? Go back to the E85 map?

There's still 93 in the tank, so that can't be the good, can it?

That's about it... I guess I could carry a 5g jug in the trunk, but that seems... dangerous? It would be sitting above the exhaust, which isn't the coolest of places :0

 

basically you have the answers to all the questions so let me fill in some of the extra data. It generally takes almost 2 tanks before the car will be back on pump or back on E85. On long trips I generally throw a 5 gallon jug or 2 in the back and secure them. I have been more occupied with worrying about fumes than a crash, but it doesnt boil in the back or anything.

 

As long as you have the ability to switch between tunes, its no biggie if your gasoline is diluted with a bit of E85 or if your E85 is diluted with a bit of gasoline. Fuel trims will compensate to make cruise and idle work properly. For WOT, I've found that my E85 tune works fine for ethanol content anywhere from 65-80% actual ethanol content. A pump gas tune run on gasoline with a bit of ethanol is safe for WOT too. The only time I think you might have some trouble is if you find yourself in a 40-50% ethanol no-man's land. You'll still be able to drive the car (probably on the gasoline tune), but idle will be rough, and spooling up the turbo probably should be avoided.

 

Ya, my only real concern is when I go to tracks that are a drive away where there's no E85 available. It seems like I either just do the track day on 91/93/105 ($8+/gal!) or I get a lot of jugs

 

I generally switch back to 93 for track days.... I got a barrel and pump for the last one, but was to tired after the build failure to even take my car out let alone deal with switching everything.. we( evolution dynamics) will be bringing e85 with us, so if you get some jugs or a barrel you could likely throw it in the truck or something.... We need to keep the pressure on the local tracks to start carrying E85.... I bet once it gets more popular in the domestic car world they will start getting it..


I have found the same results MrFred describes.... you just have to be a little smart about the transitions... just take it easy for a tank or so... you have a wide band watch that..... but I have gone back and forth several time with out much issues at all... mostly with cruising and idle....

 

mrfred: Are you saying you probably don't need to retune between E85 and E70?

OP: you will definitely want to get some 5gal. jugs for track days. I carry 30 additional gallons of E85 with me to the track. That gives me over a full tank there and a full tank for the ride home. I guess there are some safety concerns with having all that in the trunk, so I just try to be extra cautious. It's really no different than carrying gas for a lawnmover/whatever. You really don't want to switch back and forth a lot if you can help it (at least I don't). And trust me, once you run E85 at the track you'll never want to switch back

 

My car is tuned for 74% ethanol fuel (according to my ethanol content gauge). After my first fillup on E85 coming back from a road trip on gasoline, ethanol content was reading around 62%. At WOT 62% eth, AFR had richened to about 11.3-11.5 (vs 12:1 at 74% eth), there was no knock, and power was great. Power might have even been a little better than at 74% eth.

 

in general, when goofygrin reffers to the track, its a road course. in which case, 30 gals isn't going to be enough E85. 4 20 minute sessions will down about 10 gals a session. unless he just fills up with 93 for the ride home. regardless carrying 30 gallons of e85 in your car isn't a wise thing to do.

 

I was referring to a road course as well . I went through ~20 gallons in an hour of drive time, then filled it up again and drove home. I dumped in one 5gal jug for each of 4 sessions which was 15 minutes. I'm not saying carrying fuel is a good idea, but it worked for me.