quote:

Originally posted by Goob:
Ethanol is an octane booster, but not the kind of octane an engine really likes.
The Ethanol free "premium" I can buy local is only 90 R/M2 rated.
Our '18 Acadia says it will run on 87, but it's 10:1 + static compression, I think it appreciates some octane.

My Yukon Denali really likes the e85. Figures in the middle of corn country there aren't any stations near me carrying it. LOL.

quote:

Originally posted by Bucky:

quote:

Originally posted by Goob:
Ethanol is an octane booster, but not the kind of octane an engine really likes.
The Ethanol free "premium" I can buy local is only 90 R/M2 rated.
Our '18 Acadia says it will run on 87, but it's 10:1 + static compression, I think it appreciates some octane.

My Yukon Denali really likes the e85. Figures in the middle of corn country there aren't any stations near me carrying it. LOL.

As it should!
It's liquid compression at 147% fuel required, and the cooler intake temperatures. The performance gain is not from octane or timing adjustments,

I accidentally pumped possibly 3 or 4 gallons of water into my car a while back, it stumbled along real bad, I put about 2 1/2 gallons of E-85 in and cleared it up in a few miles.

This message has been edited. Last edited by: Goob,

quote:

Originally posted by Goob:

quote:

Originally posted by Bucky:

quote:

Originally posted by Goob:
Ethanol is an octane booster, but not the kind of octane an engine really likes.
The Ethanol free "premium" I can buy local is only 90 R/M2 rated.
Our '18 Acadia says it will run on 87, but it's 10:1 + static compression, I think it appreciates some octane.

My Yukon Denali really likes the e85. Figures in the middle of corn country there aren't any stations near me carrying it. LOL.

As it should!
It's liquid compression at 147% more fuel required, and the cooler intake temperatures. The performance gain is not from octane or timing adjustments,

I accidentally pumped possibly 3 or 4 gallons of water into my car a while back, it stumbled along real bad, I put about 2 1/2 gallons of E-85 in and cleared it up in a few miles.

Actually it is from timing adjustments. GM gen IV ecu’s add multiple degrees of timing everywhere based on ethanol content. It’s also probably from the octane. On 87 they will knock learn down to the low octane timing tables which will be multiple degrees lower timing as well. Easily 5-6 degrees difference between High Octane timing tables with ethanol adders vs. low octane low ethanol.

quote:

Originally posted by BJs Wild Ride:

quote:

Originally posted by Goob:

quote:

Originally posted by Bucky:

quote:

Originally posted by Goob:
Ethanol is an octane booster, but not the kind of octane an engine really likes.
The Ethanol free "premium" I can buy local is only 90 R/M2 rated.
Our '18 Acadia says it will run on 87, but it's 10:1 + static compression, I think it appreciates some octane.

My Yukon Denali really likes the e85. Figures in the middle of corn country there aren't any stations near me carrying it. LOL.

As it should!
It's liquid compression at 147% more fuel required, and the cooler intake temperatures. The performance gain is not from octane or timing adjustments,

I accidentally pumped possibly 3 or 4 gallons of water into my car a while back, it stumbled along real bad, I put about 2 1/2 gallons of E-85 in and cleared it up in a few miles.

Actually it is from timing adjustments. GM gen IV ecu’s add multiple degrees of timing everywhere based on ethanol content. It’s also probably from the octane. On 87 they will knock learn down to the low octane timing tables which will be multiple degrees lower timing as well. Easily 5-6 degrees difference between High Octane timing tables with ethanol adders vs. low octane low ethanol.

True on both. They have an alcohol sensor and a different timing table.

Well, not exactly...

Gen ivs use a virtual sensor. When the ecu sees the fuel level higher than last time it disables closed loop and then adjusts the stoich value in its calcs over the next few miles until the o2s go back to switching properly. It then sets this as the new stoich, translates this to an ethanol content, then goes back to closed loop.

I was trying to tune my wife’s suburban and couldn’t figure out why it all of a sudden wouldn’t go closed loop after I filled up so I went searching and found this little nugget.

So, I would recommend if you are near empty and running on 93, then fill up with e85 that you drive carefully for a few miles. If you go WOT coming out of the gas station you’re putting a lot of faith in the knock sensors.

Also if you turn the car off shortly after your fill up it terminates the ethanol content learn and you may be relying on a bunch of fuel trim until the next fill up. So if you go from e85 to 93 and shut it off right away for some reason, you’ll be dead rich at WOT because a lean fuel trim doesn’t get carried into Power Enrich at WOT.

I had no clue there was this much going on in the new cpus until I started hacking them recently. Kinda fun.

Great info!