wideband stoich question

[thebeewantsboost]

if i change my stoich to14.4(because of 10%ish ethanol) will my aem uego still show 14.7 as stoich?

[saltnvinegar6287]

I have the same question. If I am running stoich for 10% ethanol, and my computer is commanding 14.4, will my wideband work in a way that it reads 14.7 because it only knows oxygen content based on gasoline and not actual afr for other fuels? Am I understanding your question right thebeewantsboost?

For that matter, will the narrowband operate in the same manner? I have a PLX wideband and have similar experiences. If I remember correctly my narrowbands still look for 14.7 too even though its commanding 14.4.

[thebeewantsboost]

yeah you understood my question correctly

[thebeewantsboost]

it seems incredibly hard to get any help on this forum recently... but from my research it looks like. a wideband oxygen sensor reads lambda and then translates to 14.7 for stoich (if setup for gasoline)... a regular oxygen sensor also reads stoich or "lambda" if the stoich of your gasoline is actually 14.1 its going to hafta burn more fuel but its goal is to reach "stoich" it doesn't see numbers it sees the perfect combustion conditions. (lambda)

so when your gasoline has a stoich of 14.4 and it has reached the stoich. your gauge see thats its at lambda and converts the voltage signal to gasoline afr stoich, showing 14.7.

if everything i said is correct. do i need to adjust my wideband pid in any way to accomodate. because if my stoich is set in the editor for 14.4 and my results shows up in the scanner as 14.7 and i use that data to change my tune wouldn't that make it rich?

[5_Liter_Eater]

Yes your AEM will still show stoich as 14.7. With the AEM the only options are gasoline and lambda, settable via the POT on the back of the gauge. I'm not sure how configurable the PLX is but if its set for gasoline it will act the same. Some widebands such as the Lx-1's from Innovate allow you to configure stoich with software. I want ot say the PLX is too but I have no experience wiht it. There is such a little difference between 14.4 and 14.7 that I would not really worry about it. When you start tuning for E85 though it's easier to tune in terms of lambda. Go ahead and use 14.4 as stoich in the tune but realize that the wideband is representing lambda as 14.7.

Narrow bands will adapt to the fuel. All they really know is richer or leaner than stoich for whatever fuel you're running.

[thebeewantsboost]

do i need to adjust the scanner to read 14.4 when the gauge is reading 14.7?

[Overkill]

I didn't understand this either ^^^

14.7 is 14.7, 14.4 is 14.4, the wideband should read what it is. I've changed the stoich value in the PCM and it doesn't change on my wideband; I still get 14.7 or 14.6 out the tailpipe, even if the scanner shows the change in stoich. Multiple vehicles and ECMs, I've yet to understand why stoich never changes from 14.7 out the tailpipe.

[BennyHHR]

This concept gets many confused.

Whether it's the OEM narrowband or an aftermarket wideband, what they read is lambda, regardless of the fuel actually used and stoic is lambda = 1 for any and all fuel compositions.

The widebands typically display pure gasoline AFR of 14.7 at lambda = 1.

I'm sure Greg Banish will, at some point, chime in as he has in the past saying that tuners need to start thinking and tuning with lambda and forget all about AFRs.

With talk about E15 coming soon, this will only get more confusing for the AFR diehards.

[5_Liter_Eater]

It is hard to get your head around. All the sensors, wideband and narrow band alilke, read in terms of lambda. The wideband display is hard coded to turn lambda into AFR with the assumption that 14.7:1 is stoich. So whenever a fuel other than gasoline is used, it will not display the true AFR. You could put pure methanol in the tank and it would display stoich as 14.7:1 even though its more like 9.8:1. Thats why if you're going to mess around with fuels or blends other than pure gasoline its easier to think in terms of lambda. What makes it even more confusing is that if you tell HPT that 14.4:1 is stoich then your AFR error is calculated off of how far off from 14.4:1 you are (when not in PE) or if you command 13:1 in PE then it will tell you how far off from 13:1 you are but based off of stoich being 14.4 and the WB is telling you the AFR is 13:1 based off of stoich of 14.7... The narrow bands will still be OK because the fuel trims will be based off of lambda. All narrow bands know is richer or leaner than lambda.

[thebeewantsboost]

so i guess the answer to my question is that i should change the voltage settings for my wideband in the scanner to read(my stoich) 14.4 when the gauge reads 14.7.

[murphinator]

I've yet to understand why stoich never changes from 14.7 out the tailpipe.

regardless of fuel if the narrowbands are in play they will correct the tune to stoich (via trims) in closed loop and if your wideband is setup to display in air fuel ratio based on a gasoline scale its going to read 14.7ish

[thebeewantsboost]

so i guess the answer to my question is that i should change the voltage settings for my wideband in the scanner to read(my stoich) 14.4 when the gauge reads 14.7. ??????????
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[5_Liter_Eater]

IMO that will only serve to confuse things more. Also I don't know that it is as easy as shifting the offset. The slope may change as well? Not like you could run E85 and just change the offset to read ~10 when the gauge reads 14.7. If you're going to go through the trouble to account for the .3 difference in stoich you should start tuning in terms of lambda.

[thebeewantsboost]

i guess there is a possibility of the whole slope changing. i'm initrested in tuning in lambda but im just unaware of how friendly lambda tuning in hptuners is. i haven't been able to find a good lambda tuning for dummies.

[5_Liter_Eater]

There is a little bit of work to get there. You need to create a custom PID for commanded lambda which is just 1/commanded EQ. Then you need to create a lambda PID instead of an AFR PID. So for the AEM that would be V/7.317+.683. Then you'll need a custom PID for % lambda error which is the same as the built in AFR error PID but using the commanded lambda and actual lambda PIDs you just created.

[Overkill]

regardless of fuel if the narrowbands are in play they will correct the tune to stoich (via trims) in closed loop and if your wideband is setup to display in air fuel ratio based on a gasoline scale its going to read 14.7ish

I suppose I should separate my question into a new thread to disclude the difference when using a different fuel type.

Say I have 91 octane gasoline in the tank and I'm running closed loop. Factory stoich is programmed 14.63-14.7 on GM cars, and I'll see 14.6-14.7 on my LM1 in the tailpipe. If I change that stoich to 15.0 and flash the computer, and I see 15.0 on my scanner, I still see 14.6-14.7 out the tailpipe.

[thebeewantsboost]

Thanks for that 5 liter eater. I had found a few things on setting it up. And since u gave me exactly what I need. I guess I'm good there... Which is great cuz I'm not the best with that stuff... Something I don't get is commanded lambda. 1st off I'm not sure what commanded eq is, I don't believe I've ever come across that. And I guess the idea off commanded lambda is just weird because I didn't think lambda was something u chose... The idea is making me scratch my head a little

[5_Liter_Eater]

In lamens terms, EQ ratio is stoich over commanded. So When you want to command 13:1 you command a PE ratio of 1.13 (14.7/13, assuming stoich is 14.7). When not in PE you're commanding 14.7:1 so 14.7/14.7=EQ of 1. Lambda is the inverse of EQ ratio. Commanded lambda is perhaps a misnomer but basically it is the inverse of the PE EQ ratio. So commanding 13:1 with stoich of 14.7 would be 13/14.7=.88 lambda. Most agree that best power comes at ~.85 lambda. Its just that the PCM commands fuel in terms of EQ ratio rather than lambda so you have to create custom PIDs to be able to tune in terms of % lambda error.

[murphinator]

I suppose I should separate my question into a new thread to disclude the difference when using a different fuel type.

Say I have 91 octane gasoline in the tank and I'm running closed loop. Factory stoich is programmed 14.63-14.7 on GM cars, and I'll see 14.6-14.7 on my LM1 in the tailpipe. If I change that stoich to 15.0 and flash the computer, and I see 15.0 on my scanner, I still see 14.6-14.7 out the tailpipe.

correct , if your in closed loop you can change stoich to any value and the narrowbands will report back either rich or lean of lambda 1 and the pcm will trim it until they see 14.7 or very close to it

you could run 50/50 e85 in a lot of cars and the trims will still bring it back to reporting 14.7 or very close to it when in closed loop , open loop the 02's dont have control to bring fueling in line and things can get dicey if you havent adjusted stoich and or other methods to hit your target AFR

[thebeewantsboost]

so theoretically changing your commanded stoich alone. won't do anything for your tune? If in closed loop, outside of PE, i commanded 13.0. the oxygen sensors would still shoot for lambda.?
if i really wanted that 13.0 stoich. i would hafta tune the maf/afr error til it goes for the 13.0?

thanx 5litereater. you are a wealth of knowledge. do you know at what lambda a boosted application is supposed to see the most power? can i assume .88 lambda is about as lean as you personal tune PE?

its really nice to be able to ask that question and not hafta tell you what what type of fuel im running!! haha. i h aven't actually started tuning yet because i need to finish my exhaust but, i'll be there soon and you better not go anywhere lol!