No-ethanol gas, Superchips tuner, & octane

[UncleS2]

For the last 3-4 tanks, I've run Super Unl 93 oct gas(ethanol) & the Superchips Performance tune(91 octane req) in my 02 Dakota 3.9 V6 ATx. All gave mid-17s mpg.

Turns out there's a small independent station ~8 miles away claiming No Ethanol gas.

After a talk with the owner, yesterday I began an experiment. I filled the tank with their Regular- held 19.94 gal + ~4 oz Fuel Power, into a 22 gal capacity tank. I then reset the Superchips- but instead of setting it to the 87 octane tune, set it to Towing(91 oct req) instead. That should have more timing advance than the 87 oct tune, but less than the Performance tune.

Have driven it about 45 miles since then. Maybe it's the 2 gal of Super left in the tank, or the FP, or the combination, or ?- but so far not a hint of ping/clatter.

I may be playing with fire, but figure if it does begin clattering I can always pull over & reset the Superchips to the 87 octane setting.

And FWIW- the Dodge 3.9 V6 is something of a known "shaker". It now idles smoother than it has since I bought it 6 months ago.

Real gasoline- what a concept!

 

[gathermewool]

Unless you have a way of logging knock, dynamic advance, etc, then you're certainly playing with fire. However, I know nothing about your motor nor how your ECM deals with knock, so you may very well be safe. However, however, the difference in tunes between the regular and "towing" maps may have more to do with dynamic advance than based timing, which means you'll only really see any benefit if you're putting some load on the engine. That means you'll be risking knock and potential engine damage for no gain in fuel mileage. All speculation for conversations-sake, so take what I say with a grain of salt.

For my turbo Subie, I'm seeing very slight amounts of knock at mid-low load, and that's enough for me to reflash to the 91 octane map using 93 oct fuel.

FWIW, ethanol laden fuel has a higher overall octane than regular fuel.