1:50,75 AFR-- no knock ??

[germanvette]

My first scan is very disappointing.C6 6Speed. 2 questions about it .
I captured an OL Drive 1st gear 48%TP showing 50,75:1 for AFR at 0,872
and 0.885 Volts.spark 28.5 KR is only 0.6. How can this be … no knocking this lean.
This around 50 value appears also with lover rpm during acceIleration.
I installed a catback before I had the Scan tool.
So i rely on novice guessing. Is this possible by less backpressure only ?.
Second finding, bank 1 and 2 long term fuel trims are simular distributed
over almost all cells, but 5% apart . Looks like a different head.
The ltft #s tend to be positive, the car runs lean, okay…. But it is very fast, maybe
It could be fast already driving 200 Km/h an then accellerating.

Any ideas …

Greetings from Wiesbaden

[joecar]

GV,

Welcome to the forum... :cheers:

Which wideband oxygen sensor do you have...?

Cheers
Joe

[germanvette]

Hi Joe ,

your question is my answer. I don’t have anything other than the O2 sensors.
That means it only makes sense to look for the voltage not for the calculated
AFR-.. does it ?
What do you think about the bank difference. Is 4-5 % less over all LTFT cell
Within the normal rage.? It there a way to trim that anyway?

Thanks

[joecar]

GV,

Oh, I see, you have the narrow band O2 sensors...
So 50.75 is the commanded AFR....!?
That is very strange.
The LTFT1 and LTFT2 being 4-5% different may be due to an air leak on one bank, or something else.
What are your LTFT's...?

You can trim LTFT's by modifying the VE table B0101 and/or the IFR table B4001,
but this trimming will not make LTFT1 and LTFT2 equal each other.

You want the LTFT cells to approach 0%, and at WOT you want 920mV or a little higher.

But... without a wideband sensor you cannot see what is the actual AFR.

If you have a log, include a picture using this procedure (post #1 or #2): showthread.php?t=3064 (http://forum.efilive.com/showthread.php?t=3064)

Cheers
Joe

[germanvette]

Hi Joe ,

I still don’t know what to do about it, but I understand the data now.
If I play the log watching the LTFT table gets filled I see a quick jump to
the right side, high maps and the cells get filled downwards according
the refs .When I shift a quick jump to the left with high values typically 13,3%
for 15, 20 25 cells.
So maybe this electronic throddle ( I do what I like ) pids rule here.
The other bank then reads 10,9% or so. The difference looks worse then it is.
And its’s in red , you know. That helps to be a little shocked.
I will scan more specific, its fun.better than a videogame. :-))

P.S. there is no VE table in V2, maybe this will be an upgrade

[joecar]

Hi GV,

So left bank reads 13.3% and right reads to 10.9%... that's a difference of 2.4%... that is small and is ok.

Yes, it is much better than a video game... :cheers:

C6 Corvette may not have a VE table in the PCM... but I'm not sure of this.

Regards
Joe
:cheers:

[germanvette]

You get these high AFR Value if you scan LS2 with the GM.AFR_1 Pid.
a swap to GM.AFR_B_1 will make a almost fixed 14,7 and in open loop
you see 11,5 to 13 which makes more sense although it is no replacement
for a wideband.