Hitting rev limit too early COS5

[aaronc7]

Came across a random observation today and I can't figure out why or what's going on.

Car is a 2003 C5Z, stock OS is 12593358

I table-by-table copied my current tune to a 2002 C5 Manual trans tune file with OS 12212156

From that tune I converted over to COS5.

The tune is set to 7000 RPM rev limit. With the 12593358 based file, it works fine, as expected. With the COS5 (02020005) tune, it hits a limiter right at 6500rpm.

Did multiple back to back test to make sure it wasn't a fluke and got datalogs. My best guess is I have something weird set in one of the custom OS A series tables, but I can't find it.

Thoughts?

[ProperTuningOG]

You lifted? TPS goes down, so does rpm. RPM was still climbing when you lifted.

[aaronc7]

I agree that log looked a little funny there, I lifted once it hit some sort of 'limiter'. I didn't log accel pedal position so its tough to say how that compares to TPS. I see in the tables it talks about a separate ETC 'rev limiter' vs the standard fuel cutoff. Maybe throttle was intervening at 6500 for some reason? Just a stab in the dark. That table is set to 7k across the board though (B5401).

I did the two comparisons about 10 minutes apart and it was on the same stretch of road, same procedure, etc. The COS5 one was just hitting some sort of limiter about 500rpm sooner per the datalogs and tach.

[aaronc7]

Datalogs aside, I also tried free revving and did multiple runs and everytime COS5 was limited to ~6500 and stock OS ~7000. Fairly confident it wasn't a fluke or I was doing something different. I was just watching the tach waiting for 6500+ to shift and it hit a limiter, so it made dig a little deeper.

[joecar]

Are ETC sanity tables kicking in...?

[aaronc7]

Are ETC sanity tables kicking in...?

I AM exceeding C6101 ETC Predicted Airflow values by a little bit. The table description seems to indicate it would set a DTC vs pull power and I've never seen the code. So no idea if it's related, but I might as well bump it up a little just in case. I did increase the values of C6101 on a SD tune that I made (following the guide), but left it alone for the MAF enabled tune.

[aaronc7]

Never figured this one out. I decided I don't need the COS5 functionality, so I flashed over to my factory 12593358 OS based COS3 tune (02040003) and everything is working great. Something weird going on with 12212156 OS or COS5 on my setup it would appear.

[ScarabEpic22]

02 is 512kb, 03 is 1MB flash...the PCMs arent compatible so I'm not sure how you got the 02 OS to work on the 03 PCM?

Glad you got it sorted out, 03-07 1MB PCMs only have COS3 and only 03-05 OSs were made IIRC.

[aaronc7]

For the corvettes, it looks like only the 2004s had the 1MB flash. I have a late 03 with C6 style fuel system, but it only has 512k flash. From what I could gather from really old info on the internet, 12593358 had just a few small fixes implemented on top of 12221588, but both 512k/more or less the same.

[ScarabEpic22]

For the corvettes, it looks like only the 2004s had the 1MB flash. I have a late 03 with C6 style fuel system, but it only has 512k flash. From what I could gather from really old info on the internet, 12593358 had just a few small fixes implemented on top of 12221588, but both 512k/more or less the same.

Weird, I was under the impression 03 was a hard stop for GM to move everything to the 1MB PCMs. Good to know though!