Anything special recommended before switching to E85
 

I will be getting a tuner in this weekend...one of the capabilities is the ability to run E85. I was just wondering if there is anything special I should address before switching fuels...either for the first time or later on? Should I let the tank drain to a certain level (obviously as empty as possible, but is there a definite threshold)? Any fuel system treatments or anything? I don't plan to switch back and forth often, but I just want to make sure the transitions are as smooth and easy on the car as possible.

Thanks for any tips!

Also, if this should be posted in the tuning (or another) section, I apologize.

I think I read that you need to swap out the fuel pump/line for E85. Could be wrong though.

Let the car run down to at least the fuel light turning on. Fill with e85, switch to e85 map, drive around and let car get to the fuel light again. Fill again with e85.

You should be pretty close to the maximum ethanol content after filling up the second time. The first time you'll probably be around 55% or something like that, depending on how much the ethanol content varies in the fuel at your stations.


Summed up: The first fill up is garbage but its safe enough to drive around on as the car should be able to compensate with the fuel trims. Assuming you are running an e85. The second fill up and on will be better.


PS: your gas mileage is gonna drop considerably.

When i have people switch I have them drive till the light comes on, drive another 30 miles. Put 1-2 gallons of E85 in, flash a basemap. Drive for 30-60 miles, fill with E85, drive for ~5-10 miles at specific rpm/load to get the e85 into both fuel lines and move on from there.

Having 1 gallon of gasoline can skew your ethanol content. And although you don't fully benefit of the full octane benefits of pure e85 on NA the burn rate can be affected slightly, so its best to get the fuel you are wanting to tune on before tuning. Your tuner should be able to to instruct you about this as well!

I figured the mileage would drop...not too concerned because I don't really drive very far anyway (live a mile away from work). Just curious, though, what do people usually see for fuel mileage with E85?

I averaged 20MPG @ 3.125" pulley on my supercharger. Ive seen 16-25MPG depending on the driver & tune.

mine ranges from 18-23 but there is usually an autocross in there and lots of idling.

OK, so not too bad. That's livable in my case, for the most part. Luckily I know when a longer trip is coming up and I can plan ahead to switch back to a 93 octane map before going.

I would say the first thing to do is get a test kit and test the ethanol content at your local station / stations. That way you know what your mix is based on how much pump and E you have in the tank.

The lower the E content at your pump the less remaining pump gas you want in the tank.

I'm glad you mentioned both fuel systems needing to purge the old fuel. To switch over to E8# I typically run down to the the light and then another 25 miles (based on my gas mileage) on pump. Fill the tank with E8# making note of how many gallons it took to fill up (so you can calculate your mix). Drive for a few minutes on the pump gas map while watching fuel trims. When they hit about +15% is when i typically pull over and flash the E map.

I personally have not seen much difference in knock tendency on NA with mixes down in to the low E70 range all the way up to E90+. Fuel trims will certainly vary based on the mix though, and thus the injector scaling of the tune.

From my experience, highway mileage isn't that bad. Its just the stop and go that lowers it so much.

get a few cardboard boxes to store all your corroded fuel lines

Everything I've heard and read says that's pretty much a myth, unless you're talking over the course of 100k+ miles running nothing but E85.