if i change my stoich to14.4(because of 10%ish ethanol) will my aem uego still show 14.7 as stoich?
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if i change my stoich to14.4(because of 10%ish ethanol) will my aem uego still show 14.7 as stoich?
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.
yeah you understood my question correctly
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?
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.
do i need to adjust the scanner to read 14.4 when the gauge is reading 14.7?
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.
This concept gets many confused. :banghead:
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. :eek:
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... :eek: 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.
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.
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 14.7ishQuote:
Originally Posted by Overkill
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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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? :shrug: 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.
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.
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.
I suppose I should separate my question into a new thread to disclude the difference when using a different fuel type.Quote:
Originally Posted by murphinator
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.
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
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.
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 itQuote:
Originally Posted by Overkill
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
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!
No, changing stoich will make a difference. It tells the computer what the ratio of air to fuel is at stoich (lambda=1) and your PE is a multiplier of that. Your question is somewhat confusing but if you set the stoich to 13 and kept running gasoline the narrow bands would still switch at lambda, which is ~14.7:1 for gasoline. So it would cause your fuel trims to go negative because you are telling the PCM that you are running a fuel that has a stoich of 13 but it doesn't. On the PE side it would show up as artificially low MAF or VE values that would compensate for the discrepancy. you're seeing this now because stoich is set for 14.7 and in reality with the ethanol blend its more like 14.4.
I just read in another thread (sorry, I cant remember the source but he seemed very knowledgable) that while lean=mean with gasoline, E85 is oxygenated and likes to run rich and he suggested .7 lambda for boost and .8 for NA. .7 lambda is a PE of 1.43 (1/.7) and with an ethanol blended gas at 14.4 that is 10:1 (14.4/1.43)! :eek: So it doesnt appear that you can switch to lambda tuning and keep the same PE for all fuels. But switching to lambda alleviates the confusion of the wide band reading 14.7 for stoich.
:cheers:
Here is that thread. Pretty good reading. http://www.hptuners.com/forum/showthread.php?t=32501
this is almost just a bunch of random rambling. sometimes i think better in text, (this is what goes on in my head!) please comment on it and tell me where i'm wrong and right please.
good read sounds like outside of PE your stoich will just affect your trims. but it makes a big difference in PE. in my head, i'm thinking the narrowbands strive to make the car run at lambda and the voltages some how talk to the computer and populate your fuel trims
its a little confusing to me. how the computer knows what 14.4 is. compared to 14.7.i guess it could be like a wideband where you can program the stoich to whatever you like so lambda 1 is converted it to that number. and it just shifts tables around or something?
the trims are based off the inputted stoich and the actual lambda
if running E10 (14:1) and scheduling a stoich of 14.7(gasoline) the trims will make up the difference and without a scanner you wouldn't be the wiser.
however, you would theoretically be running lean at WOT(PE). its not really a problem because most factory tunes are pig rich for safety reasons. but it shows the importance of tuning your fuel trims.
i don't have my laptop with me. so i'm not sure. but i think i have a PE BASE AFR. and then adder tables. i will confirm that later.
e10 should be alot more like gasoline compared to e85 as far as the lean is mean thing... might just make it a smidge richer.
The effect of having stoich wrong is the same in open and closed loop. The result is you end up running richer or leaner than expected. Its just that in closed loop the trims take care of it. You would end up tuning the discrepancy out of the open loop cells so net net not a huge deal but if stoich is off by a lot then you're artificially lowering or raising airflow to make up for the difference and on an auto tranny that uses calculated TQ to determine shifting techniques (A6) that could end up bad.
Narrow bands just tell the PCM whether the exhaust gasses are leaner or richer than stoich. If its richer then the PCM decreases fuel trims to account for it and if its leaner it increases fuel trims. This happens very quickly with short term fuel trims. If a short term trim stays positive or negative for a certain time the PCM adds or subtracts that to/from the long term fuel trim. So STFT is -5 for 10 counts; PCM Sets the LTFT for that fuel trim cell to -5 and resets the STFT to 0. Then you will see the STFT go positive, negative, positive as the narrow bands report too rich, the STFT compensates, the narrow band reports too rich, the STFT compensates.
The car knows there is a certain amount of air being ingested and it knows stoich based on what you tell it so it determines how much fuel to put in. It also bases how much extra fuel to add when you command a richer EQ ratio in PE based off of the stoich and measured (MAF) or calculated (VE) airflow.
You should enter your knowns (injector flow and stoich) so you can tune to an accurate airflow number. The problem becomes some widebands being hard coded to show stoich as 14.7 which makes things rather confusing. Thats why you tune in terms of lambda. Either that or just live with the fact that lambda is really ~14.4 and your wide band thinks its 14.7.
I'm switching to an Innovate MTX-L soon. I know you can tell it what stoich is but I think it's just a dropdown for different fuels so I may still be stuck with 14.7.
do narrowbands look for your commanded stoich? or just actual lambda?
Lambda
do you think you could share a config file with me, it doesn't need to be for an aem wideband. there are just a few things as far as the pids go that i'm unsure of how to do, and it would be tremendously helpful. thanx
Attached is the config I use normally although it's not set up for lambda. Also here is a good thread on setting up PIDs and histos for lambda tuning.
http://www.hptuners.com/forum/showthread.php?t=34284
Narrowbands looking for lambda makes sense. The psuedo lean settings and changing stoich never made any difference on my wideband on any vehicle. Disappointing.
Very disappointing indeed, Will.
I've been reading through this and some other threads and I just wanted to clarify something. The narrowbands read Lambda, I got that. Is Lambda a static 14.7 (as far as the O2 sensor is concerned)? Does blended gas where Lambda is 14.4 turn my stock narrowband into reading 14.4 as Lambda?
Here's why I ask:
My LC-1 wideband shows an average of 14.4 at cruise and my LTFTs + LTFTs are +-2 or so.
If I switched to unblended gasoline(hypothetically) would my wideband now show 14.7?
I want to start tuning using my wideband and using lambda but I want to make sure I got this right. Thanks,
Pete
The wideband is not an AFR sensor, it's a lambda sensor that converts it to AFR by multiplying it by a constant Stoich (14.7 for yours) so if you are getting 14.4 on that gauge you are rich no matter the fuel. That's why you want to tune in only lambda. The gauge will read 14.7 at stoich even if you have e85 in there.
Indy,
IIRC, also remember a wideband is less accurate in lower rpms so fuel trims and AFRs between the narrowband/wideband might be a little off at cruise/idle rpms. So, its usually a good idea to tune via wideband in a more WOT setting and leaving the lower rpm stuff to the narrowbands. (Someone correct that statement if it is wrong as I cannot find the literature on it right away.)
You are correct, though wideband can get you a pretty good ballpark figure of idle and cruise stoich, it is always recommended to go back and clean up with a narrowband.