E85 vs 93 only

[87-WE2]

Not that it's a big deal, I'm just very curious why my car ran like absolute steaming caca on 93 instead of E85 last night.

Was headed out to the track (about 70 miles away) and had a little less than 1/2 tank of E85. Shoulda known better than to not fill up before leaving. Could not find e85 anywhere around the track and the track doesn't sell it. So, I went in search of e85, but was running dangerously low on fuel, so I stopped and put a gallon of 93 in. Still couldn't find any, so I ended up stopping again an putting in 4 gal of 93, disconnecting ECM, changing chips to my TT 93 chip, and turning boost down all the way. Don't know what boost ended up at with the gas because I didn't go there. Anyway my BLMs went through the roof (142), and the car idled like absolute crap...almost to the point of dying at a light. Got close to home and filled up with E85, disconnected ECM, changed BACK to the E85 chip, and started. The difference was night and day. Car ran like brand new on E85. Any ideas as to why it would run so shitty on 93? I know fueling is different in the chips, but this was absolutely terrible.

 

[3.8L V-8 eater]

You would have needed to turn your fuel pressure down as well after changing chips....I put 4 gallons of e85 in my car once (rest 93) just to try it and had to turn my fuel pressure up...You should have had to turn yours down once you put all that 93 in it

 

[DavidM]

My car likes higher fuel pressure on E85 than on 93. About 15lbs more. When I switched to 93 I had to drop pressure to get idle under control.

 

[3.8L V-8 eater]

My car likes higher fuel pressure on E85 than on 93. About 15lbs more. When I switched to 93 I had to drop pressure to get idle under control.

That's what I'm wondering....See where he changed chips but nothing on fuel pressure

 

[forcefed3.8's]

The fuel pressure should not need to be changed, but you need straight 93. There was still enough E85 in the tank to make the car run lean. Even after running the tank dry, there is still over 1 gallon in there. You could have had 4 gallons of E85 in there.
If adding E85 to 93, and running the same chip, you will have to add fuel pressure. If running straight E85 on an E85 chip, there is no need for more fuel pressure.

 

[87-WE2]

I didn't realize there would be THAT much fuel still left in it. I guess that would explain it. I've run out of fuel before, but not since putting the new sender in. I really don't know where empty is on the gauge.

I tend to get confused on the BLM issue. High BLM = lean. Got it.

For the record, I normally run the same fuel pressure with e85 as I did with straight 93.

 

[3.8L V-8 eater]

I guess I was thinking that when he went to the 93 chip he would have had a mixture of the two and would have required a little more fuel pressure...we2 what difference in BLM's are you seeing at that FP with each one??

 

[87-WE2]

My blms with e85 are normally right at 128. Friday night with the 93, they went up to 142. What forcefed said makes sense. If there's e85 in the tank and I put the gas chip in, the chip is commanding less fuel and the car is really needing more.

My lesson to learn here is not t allow myself to get that low on fuel again. I was mainly curious as to why the car ran like shit with gas. After thinking about it awhile with help from you guys, it makes sense now.