Now I am not a tuner guys. What i am asking may be something already talked about. Dont know.
My question. With the ethanol content of gas now a days (up to 10%) and the mumering of the government of maybe increasing that percentage I wanted to ask if there are any tuning issues bewtween pure gas and blended?
I know ethanol affects gas milage noticibly but I was wondering does it have and affect on the engine during open loop running?
This came to mind yesterday when I put puregas in my car and noticed a difference in the running of the car. It was almost like when you reset the ecm and do the peddle dance/room fuse removal etc. My car had a little bit of an idle search the 1st couple of cranks and my ltf's changed. They went from a 3.1 to a 2.4
Now I have ALWAYS used Shell, BP/Chevron blended gas before-never had a problem with them
WTH??
OD

AFAIK - and someone can correct me if this is wrong - ethanol is used to increase the octane rating in fuel, effectively reducing the quality of the fuel needed to reach the advertised octane rating. Needless to say it means you basically end up running crap fuel.

^^^^ Wrong in a major way. Check Wiki for correct answer
Edit... About crap fuel

Well, he is right in one way. EtOH will decrease the knock potential when added in significant amounts. You can run way more boost with E85 than you can with pump. BUt that it a different situation.

It is there to increase the effective oxygenation. How 15% or even 20% will effect a NA tune, is likely to be minimal. It might make your high boost tune a little safer.

OD, i dont remember where but it has been talked about and iirc was all explained well. sorry i dont remember where though, hopefully someone knows cause GL searching for it lol

Ethanol in the gas is suppose to help clean the fuel system and injectors.

Ethanol in the gas is suppose to help clean the fuel system and injectors.

And eat at your plastic and rubber bits inside your fueling system.

And eat at your plastic and rubber bits inside your fueling system.
Ethanol has been in gasoline for 10 yrs. The cars made today are engineered to handle it.
Edit: Actually closer to 30 yrs in some areas.

yep cars have been running it for a while.
ethanol does have a lower energy content than gas by volumne evidenced by decreased gas milage.
so my question is
"during open loop running does this 10% per volumne of ethanol affect tuning versus puregas"?.
Open loop is without a/f feedback and trims per se--right?
IMHO is HAS to affect the tuning. By what amount I am not sure.
From what I understand ethanol 10% only increases octane by 1.
It seems to me some of the missing fuel economy and maybe some of the missing hp is from using this blended gas?
Has anyone else noticed any change in their car when using puregas?
By the way I am running an FI car.
OD

Too much is bad. Let's hope they don't tinker with Super Unleaded much. I like my toys...

i searched and Rotory God started a thread back in 9/2009 in which he did find in fact that ethanol does affect the open loop tuning. He had to add over 3% fuel to his car at that time to get his a/f back to where they were. The ethanol was leaning his out.
apologize for the repeativness of this question but with more and more people doing FI now maybe this needed to be revised?
OD

Uh, pretty simple math.
Gasoline has a stoichiometric value of 14.7:1, give or take.
Ethanol is 6.47:1.
E85 is about 9:1, depending on the real blend (winter, summer, whatever).

What does that tell you about a system that is designed around the use of gasoline?

I find this thread kinda odd. I neer gave this a thought untill about amonth ago when i made a trip to texas. Somewhere in OK i noticed a sign saying " we have real gas". Cought my interest and realized that there was no ethanol in the gas. In iowa i dont think that you can by ANY "super unleaded" without ethanol in it.

Uh, pretty simple math.
Gasoline has a stoichiometric value of 14.7:1, give or take.
Ethanol is 6.47:1.
E85 is about 9:1, depending on the real blend (winter, summer, whatever).

What does that tell you about a system that is designed around the use of gasoline?
heh, I hadn't considered that aspect. That is the most important part, really. Everything else is secondary. (Basically, with a given mass of air through the maf, the more EtOH you have in the gas the more fuel you will burn in total, until you have way too much air/oxygen for the mass of fuel. All on a mass to mass basis, obviously. Not sure what this would mean in a MAP system, but likely similar.)

Ok so do tuners have different maps for puregas versus blended?
Or maybe a better question is --should they?
Does blended gas require a different thinking of the a/f's?
OD

ni dont think so.... modern ECUs operate on Lambda not AFR. lambda is non fuel specific

Lambda is not fuel-specific AFTER you define which fuel you are using. So it kinda is fuel specific; you just don't know which one.

ah, lol guess that makes sense kinda

I thought O2 sensors would keep the AF ratio at the correct value.

open loop doesnt require an a/f sensor,
And now my ltft's are at ZERO. I repeat from a 3.1 for some time now to a ZERO in 5 drive(short) drive cycles.
Damn,
OD

Your injector tables are built on a 14.7:1 ratio to hit a lambda of 1.
Fuel trim will fix the deviation in theory until you hit the limit (25%).

A change in long-term fuel trim of 3% is statistically insignificant. I vary that much from day to day when the weather is variable.

this was the same day! By drive cycles i meant crank drive, turn off, Then crank and drive again,
This occurred over about a 6 hr period.
My ltft's usually dont change much--go figue? Not at the same rpm/temps and load.

i think you are making a mountain out of a mole hill.

so what if your trims changed from 3 to 0. thats what trims exist for in the first place...

didnt mean to do that.

I understand what MM is saying, so I guess that kinda sums it up for DD.