Flex fuel tune vs E85 only tune

[Sasuketr]

So on the same day, same dyno you swapped fuels and made more power on 93? I find that a little hard to believe with how cool E85 burns...it's automatic power.

Yup had e85 in the tank and it was the fifth full tank with e85. Computer was fully adapted giving me a/f of 9.8 10 on idle. My car also has 170 deg thermostat and tuned for that, so the cht's don't go above 185 degrees on dyno runs. Car put down low hp and torque everywhere on the curve. My reasoning was Lund tuned my car with 93 octane 3 times with the FF tune, and after i gave them my datalog on e85, they said it looked ok. However, i was getting same advance spark timing on 93 vs e85. 30 degree max and same on the midrange. My knock sensors on E85 was always showing high negative values compared to 93 octane though. I could have asked to push the spark timing beyond 30 degrees.

It is not hard to believe that you can get more hp and torque with 93 octane vs the e85 on same spark timing. Even though you are burning more e85 with the flex fuel tune, maybe the injectors are maxing out. Energy density of 93 octane is alot higher than e85. It does make sense. Boosted applications though it will favor the e85.

Sponsored

 

[Silver50Pony]

Anyone have a harder time with cold starts running a full tank of e85? Mine has to crank a few times and bogs a little before firing up...is that normal for the FF tune?

 

[V8EATR]

Yea that's totally normal. Mine does the same thing.

 

[dubster99]

Normal on E85.

 

[Silver50Pony]

Anyone think it's bad for the fuel system to run e85 constantly? Or it should be ok? I hear that the ethanol absorbs lots of moisture

 

[Lonmon]

I switch mine back to 93 for the winter. About ready to switch back to e85 now. Most e85 stations run less percentage ethanol content in the winter as well. I like to wait for the summer blend (closer to actual e85).

 

[wireeater]

I switch mine back to 93 for the winter. About ready to switch back to e85 now. Most e85 stations run less percentage ethanol content in the winter as well. I like to wait for the summer blend (closer to actual e85).

Most tuners say anything over e65 blend isn't really that noticeable as far as performance over e85, so if you are running a flex tune it shouldn't really matter that much. Car feels no different running e85 now than it did in the winter. Now if you are running a straight e85 tune, then ya I wouldn't run winter blends.

I run 2/3 tanks of e85 then one tank of 93 usually. I imagine the worst part would be people who park outside during the winter because cold starts are a little long on the flex tune. I park mine in the garage and even then it takes quite a few cranks during the cold days.

 

[Shadowblackbeast]

The difference between E85 and winter E70 is negligible on the flex tune.

You can even run E70 on the E85R Lund tune you will just be a tad rich.

 

[craigsix]

my 2017 had lund ff and a e85 race tune. the race tune had driveability issues and ran the same as my ff tune at the track so i never used it.

Sponsored