“Un-commanded” AFR at WOT

[Rontune]

Recently converted a 99 vette “12584929” OS to a 02 “12212156” OS. Transferred most setting over from previous tune. Every thing works except commanded AFR suddenly drops to 11.70 about 2/3rds thru a quarter mile run, and remains at 11.70 until the end of the run. Wideband O2 confirms the drop. Can’t find anything in the tune that should cause this, and it didn’t occur in the previous tune. B1208, B3603, B3605, B3618 & B3659 are all well above 11.70 where this occurs. I am sure I am missing something, but can't find it. Some help would be appreciated. Thanks.

[5.7ute]

Does your OS run Cat Overtemp Protection? If so have you turned {B0701} to disable?

[Rontune]

5.7ute, thanks for reply…I run Random Tech cat converters. B0701 is enabled, but temp settings have been increased significantly. Stock 02 Z06/my settings degreesC = low 830/859, medium 840/867, high 850/889 & extreme 920/920/. I can disable, but all fall back AFRs mentioned in intial posting are well above 11.70. Also, have never had AFR reduction with same settings before conversion from 12584929 99OS to 02OS 12212156.

[5.7ute]

Can you post up your tune file? Have you tried setting B3701 to disable & seeing if the problem persists?

[joecar]

11.7 does sound like COTP and/or PPM.

[Rontune]

5.7ute…no I haven’t tried it with B0701 disabled. Will try this weekend at the strip. Don’t really have a place to run the car out around here.

Joecar, does “COTP” mean converter over temp? If so, when I click on B0702 the description above it says “The calculated low threshold temperature that the catalytic converters can reach before steps are taken to reduce the temperature.” Is this some internal routine/steps that the computer does that EILive has no input to? As I mentioned in my initial post, all the AFR controls (B1208, 3603, 3605, 3618 & 3659) are all set well above 11.70. I have looked throughout Engine Calibration & Engine Diagnostics and cannot find an AFR setting of 11.70 anywhere. Is there one I am missing?

Thanks for replies guys. Do appreciate. I have been chasing this for a while now. Like I mentioned, I set the cat temps up so I wouldn’t run in to them, and didn’t at anytime in the 99 operating system. But maybe it is happening in the 02 operating system. I’ll disable B0701 this weekend and see if that cures the problem. Thanks.

[joecar]

B3659 PPM is usually set to 11.7.

I just remembered that COTP may not be reflected in the commanded AFR...
and now I have forgotten if I remember or not, I'm not sure anymore...:doh2::doh2::doh2:

[Rontune]

Joecar…My B3659, piston protection, is set at 12.947. Also, where this is occurring, the rest are set at B1208=12.947, B3603=12.947, B3605=12.947, & B3618=12.46 to 12.72. I am set up with functioning MAF sensor, not SD. Hope that helps.Thanks.

[5.7ute]

Joecar, chris81 had this same issue & it was COTP causing the problem. But I am also pretty sure that when my car hit COTP it didnt reflect in the commanded AFR. Confusing to say the least.

[Rontune]

Joecar & 5.7ute…Went to the track today. First run with B0701 enabled. Same problem, fixed 11.70. Second run, B0107 disabled. Cured the problem. Tracked Commanded B3618 AFRs. Thanks guys. Was a little surprised that this problem showed up on 02 operating system since never had this issue, same setting, on 99 operating system. In any case, problem solved. Thanks again.

[joecar]

You disabled B0701 and AFR then matched B3618 (which would be richer than B3605)...

see... COTP is reflected in the commanded AFR (PCM probably selects the richest AFR of any table that activates)...

It's a little confusing because it doesn't always show up and there's no discovered COTP AFR table.

[Chris81]

Yup, same problem I had.. I've left mine off from now on and my commanded AFR stays exactly where I tell it to.

It looks like there has to be something in the PCM that hasn't been found, or that we can't have control over that is taking control of the AFR when the cat temp rises.

[c5mtl]

:cucumber:

[joecar]

Yeah, we're learning all the time...:)