Which stoichometric AFR do I use for PE table / knock enrichment?

[steelmesh]

E78 1.4T M32

Do I use the commanded Stoich AFR set by the table under Fuel>General?

For example, under 0.00 % and 6.25% Alcohol Composition there is 14.12988 AFR stock tune. So if I wanted to command lambda 0.7823, it would be 14.12988 / (0.7823*14.12988) = 1.278 that I input in the table?

[cobaltssoverbooster]

pe is a multiplier table so as you are finding out if you want richer afr you would enter numbers larger than 1 (pe value > 1 = richer / pe value < 1 = stupid lean)

pe is calculated by taking your desired target value and dividing it into your preset stoich afr. so just for example: if you want a wot afr target of 11.5 afr then take your 14.12988 and divide it by 11.5 → 14.12988/11.5 ≈ 1.22867
your pe table value would be 1.22867 or sometimes its not that well defined so 1.229. this can be interpreted as adding 22.9% more fuel to the base afr of 14.12988.

now be careful because some 1.4t cars are not factory flex fuel and thus do not have an active alcohol composition sensor. the computer more or less guesses which is kind of shitty to be honest. you can verify its activity by checking that the comp sensor is enabled or by checking for disabled comp sensor codes in the dtc list.
after mode verification verify your pe changes by calculating the resulting afr for non-alcohol and alch comp correction under pe. whichever is the closest after the adjustment will give you solid verification what its doing(this way if the sensor is disabled and it kind of tracks with the alcohol scale you know the computer is guessing alcohol value). you can use the scanner alch composition % to determine what cell the ecu would be using; keep in mind the ecu is smart enough to blend cells.


*addition: most people disable knock enrichment (KE) due to tease in tracking commanded afr targets. you work one table at a time which means sometimes you have to shut others off to isolate the control table.

[steelmesh]

pe is a multiplier table so as you are finding out if you want richer afr you would enter numbers larger than 1 (pe value > 1 = richer / pe value < 1 = stupid lean)

pe is calculated by taking your desired target value and dividing it into your preset stoich afr. so just for example: if you want a wot afr target of 11.5 afr then take your 14.12988 and divide it by 11.5 → 14.12988/11.5 ≈ 1.22867
your pe table value would be 1.22867 or sometimes its not that well defined so 1.229. this can be interpreted as adding 22.9% more fuel to the base afr of 14.12988.

now be careful because some 1.4t cars are not factory flex fuel and thus do not have an active alcohol composition sensor. the computer more or less guesses which is kind of shitty to be honest. you can verify its activity by checking that the comp sensor is enabled or by checking for disabled comp sensor codes in the dtc list.
after mode verification verify your pe changes by calculating the resulting afr for non-alcohol and alch comp correction under pe. whichever is the closest after the adjustment will give you solid verification what its doing(this way if the sensor is disabled and it kind of tracks with the alcohol scale you know the computer is guessing alcohol value). you can use the scanner alch composition % to determine what cell the ecu would be using; keep in mind the ecu is smart enough to blend cells.


*addition: most people disable knock enrichment (KE) due to tease in tracking commanded afr targets. you work one table at a time which means sometimes you have to shut others off to isolate the control table.

- P0178 and P0179 are Not enabled from the stock tune
- Under Engine > Fuel > Open & Closed Loop I note that Flex Fuel drop down is disabled and the fuel sensor is set to Virtual
- For now I set the enable temp very high for Knock Enrichment, thank you for the advice to focus

The whole EG Ratio (Alcohol) table is filled with 1.000, is that expected?

I will steal the terminal block from my other car and get the WB data scanned...I kinda maybe think I know what you're talking about verifying it

[cobaltssoverbooster]

yea they shut the alch comp system down. under virtual mode if the engine sees no vacuum changes, no premature detonation events and can correct for the fuel ratio by trimming it will skew the trims by adding a virtual alch comp value. Its a pain in the ass when it tries to wander around figuring out fuel but if you fix the tables to treat alcohol the same as pump gas then it should not wander on you. Downside you cant run e85 as a blended tuning option, you will have to have designated tune files.

someone tried to upgrade the system to have an actual blend sensor inputting data but they had a little trouble getting the computer to switch correctly between the tables and ended up going back to the stock virtual programming. if you add one in and get it to work that would make you the first i know of finishing the conversion.

[steelmesh]

yea they shut the alch comp system down. under virtual mode if the engine sees no vacuum changes, no premature detonation events and can correct for the fuel ratio by trimming it will skew the trims by adding a virtual alch comp value. Its a pain in the ass when it tries to wander around figuring out fuel but if you fix the tables to treat alcohol the same as pump gas then it should not wander on you. Downside you cant run e85 as a blended tuning option, you will have to have designated tune files.

someone tried to upgrade the system to have an actual blend sensor inputting data but they had a little trouble getting the computer to switch correctly between the tables and ended up going back to the stock virtual programming. if you add one in and get it to work that would make you the first i know of finishing the conversion.

If I am understanding correctly, with the fact I won't ever run E85, you're proposing to update:

Engine > Fuel > General > Stoich AFR, change this table put 14.X in all cells so it forces it to run whatever stoich we input in all the cells?

also

Engine > Fuel > Power Enrich > EQ Ratio (Alcohol) under Power Enrichment is already set to 1.00 in all cells

[cobaltssoverbooster]

first change-yes
second change-that table is disabled from the factory, but i personally run the alcohol pe the same as fuel pe because the system in my sonic 1.4t chooses the pe offsets for alcohol when it makes a virtual alcohol adjustment. i have not figured out why it does this when it came disabled but that is how i forced it back off.

[steelmesh]

Thanks for the insight cobalt!