12P New VE Calc

[Dylan]

Been taking some logs the last few days of my VR Vommodore V8 running 12P.
Wgen playing back the logs i had a look at the new VE data as it's quite rich in some spots. I only have a narrow band O2 at the moment
so im just watching the 14.7 areas and the O2 volts vary quite a lot.

I know a wideband would be ideal.

Looking at the new VE its pulling out almost half the VE. Im not experienced much with logs untill now im hoping someone who is could take a look over and see what they think.

[antus]

I dont have time to check your logs at the moment, but how are you calculating the VE? The Calc VE function requires wideband to do what it does. I suspect your calc ve data might not be valid at all (hence why your seeing huge changes).

[Dylan]

I don't have a wide band, I'm just viewing the generated figures in the logs. I was suss on the new value as you mentioned.
The BLM'S are around 90-99.

[Charlescrown]

I haven't looked at the logs but the std O2 sensor will swing all over the place because it's doing it's job with mixture correction where the wideband is used to tell the actual mixture in the exhaust which is what you set your ve tables to.

[Dylan]

Is that what's meant by cross counts? It swings quite a bit each way, much more than I would of thought.
I will ignore the VE calc for now.

[VX L67 Getrag]

Yeah cross counts is the amount of times it's gone from rich to lean, but I'm not sure how it's calculated must just be in 30 second blocks or something!

If you don't have wideband you can disable LTFT (called something else in 808 world) & just use the STFT (again called something else in 808 world) & adjust the VE table with that, I did it with some success!

You can also flick the flag to do learn VE from narrowband but will only work in the stoich areas!

I think LTFT is called BLM & STFT is called INT in 808 world from memory!

[Dylan]

I looked at the LTFT it was taking a bit of fuel out. Didn't look at the STFT yet.

[Dylan]

Had a look at the STFT there's a bit going on, maybe not to bad. In the 14.7 area's at least.

[VL400]

There are a few things at play in closed loop, its to both manage the AFR so it == stoich and to make the cat work properly.

The INT is a short term, or fast adjustment. It adjusts fuel either + or - until it reaches a threshold, at this point the BLM gets a + or - applied and resets the INT to zero to start all over again. The BLM is a saved value while the INT is a instantaneous item. The BLM gets gets stored in a small table of non-volatile RAM so once closed loop is entered can start to trim the fuel from this value rather than having to learn from scratch again. The narrowband VE learn function uses the INT but disables the BLM. Instead of the INT reaching a threshold and then + or - the BLM it instead does a + or - to the actual VE table.

The cross counts are the number of rich/lean swings per 100ms. It is not really related to the the INT (integral or STFT) or BLM (block learn multiplier or LTFT), the cat converter needs to store and release oxygen to work efficiently so the ECU applies a bit of proportional gain to make the loop unstable and get it swinging either side of stoich. The INT and BLM just get the fuel trimmed to stoich so it can swing either side of that. When the mixture is lean the cat can store some oxygen and when rich can release it, this is part of the 3 way catalyst function.

Back to the orginal VE calc item, it requires a wideband to work!

[VX L67 Getrag]

Have you read the user guides?

If you want to actually tune you need to turn off LTFT (think its called BLM in $12p) then use the stft (think its called INT in $12p) to know where to adjust!

If there both enabled the stft work off the ltft so it's kinda useless!

EDIT: VL400 explained it better!