Analyzing log files

[joecar]

The rear O2S are the same as the front O2S (other than the plug maybe)...

you can run them in the front O2S location (front harness sockets, and ahead of the cats if present).

Beware: on Corvettes it may be possible to inadvertently swap left/right O2S connections.

Yes, accord to GM training material and the Bosch Automotive Handbook, the O2S obtain reference air thru the attached pigtail, so you can't solder/splice wiring nor use alternate wiring.

[joecar]

You could run any of these:
- 2-bar speed density with/without CL (MAF is removed);
- 2-bar MAF/VE tune with/without CL (MAF/VE/IFR tables have to be scaled to avoid PCM's MAF 512 g/s limit, and all tables referencing airmass/airflow have to be shifted).

BUT: in any case, the IFR must match the FPR (your FPR is MAP-referenced, but your IFR is sloped which does not match the FPR).

[joecar]

Mechanical stuff:

it is important to perform various diagnostics (compression and leakdown tests, checking pushrods for straightness, checking lift of each cam lobe, checking for airleaks, coolant leaks, oil leaks, checking oil consumption, etc...);

it is also important to check electrical (power/ground voltage drops, checking secondary (spark tester, oscilloscope if available));

these are imperative before performing any tuning.

[Rich Z]

So stoich should be 14.17:1? I did a log using my newly installed wideband and during cruising it appeared that the actual AFR was sine waving around the commanded AFR rather nicely. I thought that was a good sign. :(

BTW, I am using 93 octane non-ethanol gasoline in my car. There is a local Sunoco that carries it.

[Rich Z]

The rear O2S are the same as the front O2S (other than the plug maybe)...

you can run them in the front O2S location (front harness sockets, and ahead of the cats if present).

Beware: on Corvettes it may be possible to inadvertently swap left/right O2S connections.

Yes, accord to GM training material and the Bosch Automotive Handbook, the O2S obtain reference air thru the attached pigtail, so you can't solder/splice wiring nor use alternate wiring.

Interesting... How should those front O2s be connected? I have the sensor on the passenger side header running to the right side connector to the PCM, and of course the driver side O2 sensor running to the left side connector. I'm assuming that the guys who thrashed my car didn't switch the harnesses.

Also, about the pigtail, does this mean that the pigtail itself has to be exposed to open air? I believe I covered them to keep them from being exposed to the header pipes that are pretty close to them.

Did I post my most recent logs somewhere? If so how did the O2 signals look? If not, heck I can post them again....

[Rich Z]

You could run any of these:
- 2-bar speed density with/without CL (MAF is removed);
- 2-bar MAF/VE tune with/without CL (MAF/VE/IFR tables have to be scaled to avoid PCM's MAF 512 g/s limit, and all tables referencing airmass/airflow have to be shifted).

BUT: in any case, the IFR must match the FPR (your FPR is MAP-referenced, but your IFR is sloped which does not match the FPR).

Yeah, that issue with the IFR/FPR does bother me, I have to admit. My tuner didn't seem concerned about it when I called his attention to it. But I'm guessing that if I go about messing with that, then I've got zip for a tune. I'm not prepared to tackle that yet. And certainly in no position to argue with my tuner about it, neither. But yeah, I do know it is a bridge that I will need to cross sometime.

[joecar]

( the front and rear O2S are the same device, the fronts are used for bank trimming, the rears are used for measuring cat efficiency )

[Rich Z]

( the front and rear O2S are the same device, the fronts are used for bank trimming, the rears are used for measuring cat efficiency )

I've been scouring the net looking up info on this. Results are inconclusive simply because all the info seems to be based on opinion. Some say that the rear O2s will heat up faster, or slower, than the front O2s. Seems to be related to the resistance of the heating element affecting how quickly the sensor heats up. Some say wrapping the headers will help, which I have actually done recently. And some will claim that Denso, Bosch, NTK (pick one) is the only brand to use.

I think for now, I'm going to stick with the O2s I have. They are rear sensors with adaptors to mate the rear square connector of the sensor with the front straight connector in the PCM harness. I do know the sensor itself looks different, and I've been meaning to take pics to illustrate this. Since I have the exhaust off of the car, I can look right up the header collector pipes and see those O2 sensor ends.

But if I NEED to buy new O2s I will. But ONLY if I NEED to. I hope to hell I never screw up and tell my wife how much this has actually cost me. I haven't figured it out myself, just so if she asks, I can honestly say that I don't really know. But I have a good inkling. And it ain't pretty. :(

[joecar]

In your logs, MAP shows you might have an airleak, or valve timing/compression problems.

[Rich Z]

In your logs, MAP shows you might have an airleak, or valve timing/compression problems.

Well, coincidentally when I was pulling off the exhaust, I found that one of the vacuum lines on the turbo wastegates wasn't threaded in tightly. Actually it was barely threaded in at all. So that certainly would have been a vacuum leak there. But what is it in the MAP trace that tells you that, if you don't mind explaining it to me?