stoich

[deckspec]

would rasing the stoich value slightly net you better gas milage while crusing?

[WS6FirebirdTA00]

No.

[BBA]

But it would increase your fuel trims.

[KLUG'S SS]

The narrowband O2's are going to switch to keep the fueling centered around stoich (lambda =1) for whatever fuel is in the tank no matter what the stoich setting in the tune is.

[BBA]

The narrowband O2's are going to switch to keep the fueling centered around stoich (lambda =1) for whatever fuel is in the tank no matter what the stoich setting in the tune is.

True, but the fuel trims will be offset to maintain actual lamdba=1 is the stoich value is changed from the actual fuel composition. Of course this can be masked by doing a VE/MAF tune before changing the stoich value.

In short, if you change that stoich number value you will have to do a VE/MAF tune afterward to make the trims close to 0.

[S2H]

True, but the fuel trims will be offset to maintain actual lamdba=1 is the stoich value is changed from the actual fuel composition. Of course this can be masked by doing a VE/MAF tune before changing the stoich value.

In short, if you change that stoich number value you will have to do a VE/MAF tune afterward to make the trims close to 0.

negative....
the stoich value in your tune is only to output an AFR value for the commanded AFR.
if you have a flex fuel vehicle its a reference to lambda 1.0....so that your flex fuel tables can do the math for proper ethanol blends...they should have just made it Lambda in the tables to begin with....I have no idea why they didnt


it doesnt change the fact that lambda 1.0 is what the 02's switch at...

it wont change a dam thing...
take it ands set it to a stupid # like 10.0 ..... its still gonna trm exactly the same as it did before...no changes... its just going to report 10.0 as stoich in your OBD2 readings... thats it.

[KLUG'S SS]

While were on the subject I've got a perfect example, recently I decided to experiment and switch over to E85 in my truck and had all my fuel trims right around -1- -2 % on premium e10 so all that I did once I put the E85 in the tank which is actually e70 right now because of the winter blend (tested it) so I just put 10.7 stoich for e70 in my table and viola trims are right back where they were at on the e10 premium fuel.

[Twitch]

Sorry to ask you guys to dumb things down (since you pretty much answered my question ). But I've been thinking about this for a while.
If my fuel trims are reading near zero, I guess it's normal for my wideband to read low 14s AFR. And if I found gas without ethenol, the wideband would read 14.7.
Thanks

Tony

[S2H]

Sorry to ask you guys to dumb things down (since you pretty much answered my question ). But I've been thinking about this for a while.
If my fuel trims are reading near zero, I guess it's normal for my wideband to read low 14s AFR. And if I found gas without ethenol, the wideband would read 14.7.
Thanks

Tony

when you add ethanol to gas, the AFR numeric value for stoich changes to a lower AFR

so your 14ish AFR with ethanol is correct and if you get gas without ethanol its going to trim around 14.7

basically as you add ethanol the stoich AFR changes...
your trims always center at 1.0 lambda (stoich)
so when the ethanol mix lambda 1.0 = 14ish, then your trims will center around 14ish...

[Twitch]

when you add ethanol to gas, the AFR numeric value for stoich changes to a lower AFR

so your 14ish AFR with ethanol is correct and if you get gas without ethanol its going to trim around 14.7

basically as you add ethanol the stoich AFR changes...
your trims always center at 1.0 lambda (stoich)
so when the ethanol mix lambda 1.0 = 14ish, then your trims will center around 14ish...

BIG BIG help. Thank you.

[S2H]

While were on the subject I've got a perfect example, recently I decided to experiment and switch over to E85 in my truck and had all my fuel trims right around -1- -2 % on premium e10 so all that I did once I put the E85 in the tank which is actually e70 right now because of the winter blend (tested it) so I just put 10.7 stoich for e70 in my table and viola trims are right back where they were at on the e10 premium fuel.

its not quite doing what the original question was about...
you have a flex fuel table, which is a multipler for the Injhector basically..
so when you put 10.7 in the box that represents e70 its telling the injectors to add more fuel..

we're talking about vehicles that have a single stoich value and not a table that ranges from 0-100% ethanol

in a vehicle with the flex fuel table you can change the stoich AFR based on the percentage of alcohol...

in a non flex fuel vehicle it doesnt change jack squat other than the OBD2 reported AFR values.

[KLUG'S SS]

its not quite doing what the original question was about...
you have a flex fuel table, which is a multipler for the Injhector basically..
so when you put 10.7 in the box that represents e70 its telling the injectors to add more fuel..

we're talking about vehicles that have a single stoich value and not a table that ranges from 0-100% ethanol

in a vehicle with the flex fuel table you can change the stoich AFR based on the percentage of alcohol...

in a non flex fuel vehicle it doesnt change jack squat other than the OBD2 reported AFR values.

Right.

I went back through and had slowed down and read it more thoroughly instead of getting ahead of myself and realized that.

Like I had said in post #4 the o2's are going to switch around a Lambda=1 no matter what.

[Higgs Boson]

If you are running E10 and letting it run 14.6x you would be running E10 lean and maybe get a little mileage out of it (since stoich for ethanol is richer, right) but if you changed PE to command 12.0 would you make more power (and thus get two benefits)?

[WS6FirebirdTA00]

No. o2 sensors will still correct back to lambda 1.

[Higgs Boson]

No. o2 sensors will still correct back to lambda 1.

which is based on the apparently uneditable pcm setting of 14.6 or the actual fuel used (E10 - 14.1)?

[printmanjackson]

which is based on the apparently uneditable pcm setting of 14.6 or the actual fuel used (E10 - 14.1)?

UNEDITABLE?

[WS6FirebirdTA00]

No, it is based on how o2 sensors work. A correctly working o2 sensor will correct to lambda 1.

[printmanjackson]

ok, tell me if I got this right.

When I first set up my primary table in the scanner for "commanded lambda" I used commanded AFR/14.63. I tuned the MAF and VE tables. Turned everything back on and my LTFT's were off +5% to +6%.

The fuel in my area is E10 so is this the reason my LTFT are off? Do I need to go back and reset my commanded lambda using 14.2 or 14.1? Then retune my MAF and VE?

[Higgs Boson]

UNEDITABLE?

check post 6. that is telling me that you can't change the 02 sensors switching around 14.6, only the displayed commanded afr, which does nothing if the 02s are trimming back to 14.6 no matter what is "commanded."

[WS6FirebirdTA00]

Guys, o2 sensors don't switch around 14.6, they switch around lambda 1.0. Correct, you can command what ever you want but they will still correct back unless you change the switch points, which will slightly move it.