TB SS LS2 WOT Commanded PE Question

[DrkPhx]

Hi,
I have an 06 TB AWD SS and was recently going through all of my WOT datalogs and noticed something peculiar. Only mods are tuning. I don't have a WB hooked up. I'm using 92 octane gas.

On every WOT run (dyno, street and track) the logged commanded PE (AFR) is dead on until 5600 rpms or higher. After that point, the commanded AFR drops to 12.2 and 11.8 right after for the remainder of the run. Coincidently the Injector Duty Cycles jump above 80% and even sometimes to 88-90%.

What's even more odd is the AFR on the dyno sheet on the dyno runs matches the actual commanded AFR even though the logged Commanded AFR shows otherwise. Can anyone explain why this happens and maybe offer some guidance? I went through all of the parameters, but maybe I'm missing something. Any help is appreciated.

[joecar]

Probably piston protect mode (or similar) kicking in...

The extra fuel from PPM is not included in the logged commanded AFR pid.

[joecar]

And welcome to forum DrkPhx. :cheers:

[DrkPhx]

Thanks for the tip and welcome.

[joecar]

Oh, I was incorrect, piston protection fueling is included, I looked thru some logs I took last week and the AFR's linked to the PPM fueling table.

[joecar]

So the other possibility would be catalytic overtemp protection.

If you enable scantool->tunetool pid linking, then position the cursor on the event in the log chart, and in the tunetool open each of the fueling tables and see if the AFR matches what is commanded... if it does, then you have the table that is causing it.

Cheers,
Joe

[DrkPhx]

So the other possibility would be catalytic overtemp protection.

If you enable scantool->tunetool pid linking, then position the cursor on the event in the log chart, and in the tunetool open each of the fueling tables and see if the AFR matches what is commanded... if it does, then you have the table that is causing it.

Cheers,
Joe

I do have the scantool>tunetool pid linking enabled. Usually the cells(s) in the selected tune parameter is highlighted in grey. For some reason, no cell is highlighted in the commanded PE table. I'm going to go through the fuel tables again and look.

[DrkPhx]

I think I found it. The values in the Maximum VE table were lower than the values in the Main VE table from 5600 rpms and higher. This is the same rpm range where the AFR dropped.