Commanded PE question

[dvx]

I am working on PE mode for my 99 Z28, which has been migrated to a 02 operating system. It's a heads/cam/intake/headers car with 30 lb injectors, which I have rescaled the IFR table for. I have done AutoVE a few times and I think my VE table is pretty close. I made a few runs this morning in SD closed loop, and commanded AFR (and actual) is following B3618 as it should (12.75 AFR), until 5600 rpm. Then commanded (and actual) drops to 11.9. About the time it hits 2nd gear, commanded drops to 11.7 and stays there until I let off.

Why does it not stay at 12.75 as I have it set in B3618? Coolant temp was 180 degrees, which puts B3617 (PE modifier based on coolant temp) in a range of 0 adjustment. B3614 (PE modifier based on intake temp) is set to 0 across the board. Is it possible it went into piston protection mode and is using B3659 (commanded fuel when in piston protection mode)? The only possibility I can see here is that it triggered B3652 (piston protection MAF limit), which I have not changed but was not logging at the time, however the MAF was turned off and unplugged.

Please help, thanks.

[joecar]

It could be catalytic overtemp protection mode kicking in... there's a disable for this.

[dvx]

Thanks for the response. I have B0701 disabled. Is there another cat protection somewhere?

For some reason I think it's using the piston protection mode table, since it commands 11.7 AFR, which is where it goes. But I don't know why this would happen.

I went to the track tonight to work on it but got rained out. Going to go back in a few weeks, any advice would be appreciated.

[VTC_WS6]

I've had similar problems as you, my problem is repeatability or lack thereof. I've gone through the AutoVE process and I've got my LTFT down to no more than -5% LTFT for the better part, however I've noticed that WOT pulls really tend to get wacky. I'll take a pull and run a 12.3-12.5 or so, make tiny adjustment to the VE or MAF scale, make another pass and now I'm well in the 14's or something esle well out of range. I don't know if it's just the insane Florida mid-day heat or what but it's been driving me nuts seeing as WOT should be the easiest of all adjustment... in theory at least.

[dvx]

I appreciate the input. It sounds like your actual AFR is the issue. I have a slightly different issue where my actual is following commanded fairly close, but for some reason commanded does not always follow what I have it set to in B3618. I have re-enabled the maf and tweaked a few other things and now it seems to be working as it should. But I'm still stumped as to why it wasn't before.

[joecar]

Keep in mind that when PE enables, PCM probably has gone OL in which case the AFR selected is the richer of B3618 and B3605.

[dvx]

Thanks joecar. B3605 is set a bit leaner then B3618. But I have a question. Should B4206 be set to enable or disable?

[joecar]

If you want to run CL which uses LTFT trimming, then B4206 is disabled.

If you want to run "semi-open loop" (SOL) which uses STFT trimming, then B4206 is enabled.

If you want to run OL, then in addition to CL being disabled, B4206 has to be disabled.

[stigmundfreud]

Just coming back to this on mine as I'm considering disabling LTFT full stop but running CL in all but PE mode.

Presently LTFT is enabled so that will effect OL (PE) but as it was seemingly spot on at the dyno a few months back I was considering disabling LTFT which should in effect mean it uses O2s for feedback in all but PE mode yes?

If I enable b4206 it will then enable stft when in OL/PE mode? Is there any reason to enable 4206 if I am happy with my VE?

In other words (long way to ask a question) if running in CL if I disable b3801 and keep 4206 disabled will the car run semi-ol when outside of PE and full OL when in PE?

(I have 4108 enabled)