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You lost me Jeff. Best you get some rest & post it again lol.:angel_innocent:
By changing B3601 you do in effect change all the commanded fuel tables when the tunetool is reopened. Are you saying it will not change in the PCM due to the preferences being locked?
While it may not be a dramatic inaccuracy, it will explain how returning to closed loop may lead to positive or negative fuel trims, or inaccuracies when the commanded AFR is changed.
We do this regularly on E38's. From E0 to E85 and in between.
The LTFT's get the picture within a couple miles of a change in fuel from a gas station, and may raise a lean/rich DTC, but then once the stoich is reflashed by the approx % that the LTFT has moved (if the STFT's have settled back somewhere around zero) or the new calculated stoich based on estimate of what is in the tank, then the trims are mostly back in the right space again.
Its not quite a flex fuel setup.......:)
YES! Ideally, you just set your defined stoich point in the table to whatever the chemistry of your fuel really is and leave it alone. (I use 14.13 for e10, 14.64 for "normal" gasoline, and 14.4 to split the difference if we're unsure of what's in the tank)Quote:
Originally Posted by SSpdDmon
Once you've defined the stoich point, you work entirely in units of lambda or EQR for relative richness. A value of 1.0 should command whatever your predefined stoich point is for delivered AFR on the scanner. If this really matches your fuel in the tank and you've nailed both the injector tables (ALL of them) along with the airflow models, your fuel trims will be very close to zero and everything works as intended.
I can confirm that adjusting the stoich point scalar/table will indeed change the open loop fuel delivery as well as the displayed "commanded AFR" on the scanner.
When using ethanol blends (including e10), you have to break the habit of saying "I want 12.6:1 at WOT" and start thinking "I want lambda 0.86 (or 1.16 EQR) at WOT." It's the same RELATIVE enrichment, from a different stoich point; and that's all the combustion in the cylinder cares about.
Likewise, you also need to log LAMBDA or EQR from the wideband, NOT AFR. If you calculate fueling errors based on displayed AFR on the wideband divided by some modified stoich, you're asking for trouble. Further, most widebands display "AFR" by merely multiplying actual lambda by 14.64ish, which means that a displayed "14.64" on that wideband would REALLY be 14.13 for e10, since that's lambda=1.00 at the sensor. See where these start to compound? Using the "BEN factor" based on AFR just takes you a step further toward confusion in this case. That's why I log exclusively in lambda, and view GM cal tables in EQR to stay consistent even when stoich for the fuel is different.
After you save the tune values will change slightly.
Example:
14.4AFR becomes 14.42AFR.
Don't forget to change the fuel settings in your WBO2 controller to match
your new EQ1/Lambda1 and any cal_pid formulas you have relating to EQ/Lambda.
I'm saying B3601 is what it is....always AFR because that's how the PCM reads that cell. All other fueling tables IIRC are based on EQ as a default in the GM PCM (PE, OLFA, etc.). When you alter the EFI Live preferences to show AFR, it can only be done with a stoich of 14.63 because EFI Live has that variable fixed at that ratio. So, all of those other fueling tables (PE, OLFA, etc.) will be based on gasoline's stoich on your computer screen. But when they're flashed into the PCM, they should still be loaded in the default units (EQ).Quote:
Originally Posted by 5.7ute
What this means is if you change B3601, the PCM should still proportionately enrich the fuel mixture in open loop (PE, OLFA, etc.) based on how it would have been done using gasoline.
So, to sum up...
1) The GM PCM sees B3601 as AFR. You'll always see B3601 as AFR because that's what GM set it to be in the PCM. Therefore, you can adjust this for the stoich of the fuel you're using regardless of the display preferences in EFI Live.
2) You can change all of the tables that defualt as EQ in the PCM (PE, OLFA, etc.) to show AFR in EFI Live. But, they'll always show AFR based on gasoline's stoich in EFI Live.
3) When flashing the PCM, the PCM should still receive the default units (EQ) regardless of your EFI Live display preferences. This is where I started to bable about how a 13.0:1 AFR (which is really a 1.13 EQ for gasoline in the background) in your PE table will translate to a 12.46:1 AFR commanded if you were to adjust B3601 to 14.08 for a 10% ethanol blend.
#3 is no different really than when you view VE as a percentage instead of the default units (g*K/kPa). When you flash the tune back into the PCM, it's getting the default unit in the background....not the VE % of theoretical maximum numbers that you see on your screen.
I believe Greg and Jeff are saying that we should all use EQ units since the PCM works in EQ units.
I use (and have been using) EQ units... I prefer EQ over AFR.
My serial BEN's are defined as:
BEN_SER1 = {GM.EQIVRATIO} * {EXT.WO2LAM1}
BEN_SER2 = {GM.EQIVRATIO} * {EXT.WO2LAM2}
(since the pids EXT.WO2EQ1 and EXT.WO2EQ2 don't exist)
Fixed. :)Quote:
Originally Posted by joecar
Ah yes, that is what I meant.
Couldn't you use {B3601}/{EXT.WO2AFR1} = External Wideband EQ
What if the WBO2 setting for Lambda1 (14.7AFR) does not match EQ1 {B3601} exactly?
When we are setting up our WBO2 sensors Like an "whatever brand" and
it has you use 7.35 for half or .5 EQ or Lambda (look at the PID definitions and formulas in the scan,pid selection)). If the PCM kind of does the flex fuel thing as GM308 says (that seemed logical and also matches the flex fuel tables too in the later PCMs) Does that mean we cannot really use the given of 7.35 for AFR for one half of the WBO2 equation and then add what ever the WBO2 sensor says for the other half which is the actual reading? If so that suddenly does become a factor to take care of I think? I am not sure I said that right but it would seem we would have to use EQ or Lambda as Greg and Jeff say but! how does this affect the WBO2 configuration, how the 97-04 PCMs think and EFILive WBO2 PID?
98 tigershark
Quote:
Originally Posted by mr.prick