Determining if it's IAT pulling timing on base 2017 C7 non-Z51

[dvanorder_C7]

Not new to HPT but know little about the LT1. This is my personal car, and tuning is a hobby. I am drinking from a firehose compared to learning the LS1. It is a 2017 7 speed base 1LT w/1600 miles. I bought the car in February, and what a difference compared to a C5 98 LS1. However, the few 85 + degree sunny days here in TN have been an eye opener in terms of the LT1 being noticeably down on power. It is a different car in terms of throttle response. I've read lots of comments about how IAT location and heat soak may be a major culprit. I am flat guessing what PIDs to scan as there are numerous spark adders. Attached is the scan I did this afternoon. Despite not logging cylinder mass, using Excel I can see where at the highest IAT/IAT2 temps advance is down. Hard to tell why because a number of you discuss how the ECM can use derived values for calculations versus the physical sensor. The color is black, which may contribute something.

My hope is someone here would not mind offering some tips and/or hints for pinpointing/adjusting out what is reducing power when it's sunny and over 85 degrees ambient. Not looking to learn part throttle tuning at this time. Baby steps. My gosh, even the fans operate off percent versus on/off for a given ECT.

Thank you in advance.

[Ben Charles]

What part of TN?

[Harlech]

I don't normally see temp retarding until like 140 on my IAT's and I don't think I've adjusted any of that.

[dvanorder_C7]

What part of TN?

Nashville

[dvanorder_C7]

I don't normally see temp retarding until like 140 on my IAT's and I don't think I've adjusted any of that.

No doubt I'm doing something wrong because these are so different from the LS1. Is this method of analysis still valid?

1. In Excel, get the RPM, cyl airmass (spark mass), and value for Advance in row where both IAT's are higher/highest.
2. Using these values, open the High Octane table, find the Advance that should be used (what I would have done for the C5). No reason to assume Low Octane table would be in use if I am running Shell E10
3. Value in Excel is lower than what's in High Octane table, compare IAT/ECT values to the IAT and ECT spark correction tables, see what is being subtracted. Assuming IAT's are artificially high b/c sensor body absorbing heat, adjust spark correction in those cells

Also wondering if there are any common sense changes that can be made safely, i.e. GM was intentionally overly conservative. Also interesting are the tables for HPFP noise control, which I am not touching, but confirms GM is aware these things sound like pissed off sewing machines at certain RPM.

[schpenxel]

I'm really not sure what you're asking..?

The most timing that is pulled from IAT in that log is showing up as around 1.5*

You need to be logging a LOT more stuff

One thing that you're probably not used to is that on newer vehicles you can log tons of stuff without it slowing down all that much (if any), so don't get hung up on trying to keep only a few parameters in your channel list. If you're curious what it is, add it.. I've literally added every parameter there is on an E38 truck before and it still logged fine. Not sure how it would go on a C7 but yeah, add whatever you want to check out

[dvanorder_C7]

My apologies for being vague. You are right, with a '98 C5 and HPT 2.22 I only logged what was needed. The differences between that PCM and the E92A are dramatic and I don't think any of it translates. In 2004 there was a wealth of information on tuning the LS1. The LT1 only having been out 3-4 years may be why I am not finding anything like that for the E92/E92A PCM. The LT1 tunes in the repository are stock, so there's nothing to compare with mine. It was a mistake to look at IAT's, I should have just humbly asked for recommendations on where to start learning this PCM given some experience with the LS1.

If I were to download and study late Gen IV PCM tunes, or purchase an @ home class from say the Tuning School for the Gen IV, would enough translate to get me started?

Appreciate everyone's patience, I'm an engineer approaching retirement that finds this stuff really interesting.

[Ben Charles]

Your best bet is to get someone to help you who knows the new system and learn

[dvanorder_C7]

Yes--I know someone south of Nashville who may be willing to teach. The advanced help article about the new driver input/torque based model used by the E78 was very helpful. No wonder I'm not getting anywhere with sensor PIDs. Time to start scanning different PIDs. Thank you everyone.