2013 Camaro ZL1 IAT2/ IAC and base spark timing reduction questions

[turabo87]

Hi folks,

Just tuned a 2013 ZL1 with a 2.55 lower pulley, for 93 fuel. Has stock intercooler system and nothing else to cool the IAC other than what stock setup provides. I'm pretty happy how car came out, pulls hard on 1st fresh pull but starts to pull timing (no KR whatsoever, so it's pulling it from a base table somewhere). I've revised spark tables for ECT, IAT, but it still pulling about 4-5 degrees on 1st fresh pull (0.0KR) and goes pretty much downhill from there for any consecutive pulls which leads me to believe it's just heat soak, and it's evident from the logs that it's a pure timing issue (for example, I'm commanding 20 and I get 16.5 from first pull, and 12-13 from a second consecutive pull, and always with 0.0KR). I've raised IAT spark table significantly (-0.5 degree around 120-130F and linearly upwards to about -8deg at 180F or so) and it's still pulling timing. I didn't see intake air temps reaching this on the PID, but I think i had the wrong PID. I can post logs and tune later if requested, but my questions are the following:

1. Besides the IAT Spark table, is there another table responsible for adding negative spark based on IAC temps or IAT2? If it exists, I can't find it for the life of me.

2. What are the correct PIDs for logging IAC or IAT2? I tried searching it and couldn't find it either.

Thank you.

[kevin87turbot]

If you'll post your current tune file and a datalog we can help you with this.
But, in the meantime, IAT, CTS, octane modifier, torque management and burst knock and all affect the ignition timing without showing any knock sensor activity.
You'll just have to datalog all of those parameters to determine the culprit.

[turabo87]

I'll post file and datalogs as soon as I get to my laptop at home later. Is there a specific PID for IAT2 or IAC temp (post CAC). Also which is CTS and what is the PID for this? Is there a table for CTS? Vehicle is not mine and not in my custody, so I'll have to make sure to set up all PIDs again ready to go before I meet up with owner for more logs.

[turabo87]

Attached the tuned file as I left it last night and stock file for reference/comparison. Like I said I couldn't find the spark table related to retarding timing based on IAT 2 (after charge air coolers), where I think the issue is. Car drives and responds fantastic with the MAF tune (so VVE was left intact for now) and apart from the mystery timing pulled it feels great, and the fact also that we ran out of injector DC up top but that's a different topic.

Drew ZL1 wot pulled timing after hot.hpl Drew ZL1 WOT tests.hpl

[turabo87]

I guess I found my answer to the problem of missing timing; it was the IAT base table pulling timing. On the 2013 ZL1 there is not a specific IAT2/MAT spark table, so it looks like the IAT spark table works for both the intake air temp sensor and manifold temp sensor (IAT2), and it looks like it just chooses one or the other (whichever one is highest temp) for the IAT spark reduction table; this is just my theory based on what I could gather from the datalogs. Attached is my new datalog and my latest file which free'd up more timing when IAT2/MAT got hot.

Would be great to confirm this with an advanced tuner, and hopefully this will help others. Car rips now like a bat out of hell and customer is beyond ecstatic, so it was definitely the missing timing.

Drew 2013 Camaro ZL1 Calvo Tune 2,55 pulley.hpt
Drew ZL1 WOT pull final test less timing pull from IAT.hpl

[mr.mjdolan]

I noticed your MAF was at 85lb/min.
Doesn't that seem high for a LSA making 13-14lbs of boost on 93 without a cam or TB?

Im running a 2013 ZL1 also with 15.8lbs of boost on e85 with more timing and only pushing 75lb/min.

[turabo87]

I noticed your MAF was at 85lb/min.
Doesn't that seem high for a LSA making 13-14lbs of boost on 93 without a cam or TB?

Im running a 2013 ZL1 also with 15.8lbs of boost on e85 with more timing and only pushing 75lb/min.

Not sure what?s the norm on MAF flow, but the car is running like a champ. We?re at sea level too. Car put down 586WHP and 591WTQ on a dyno jet, on a hot summer day. Flex fuel is next.

[hjtrbo]

Good pick up. Op, double check actual fuel pressure is hitting commanded. Have a feeling from about 4000rpm it'll be diving away. Mine is out of pump so MAF curve is jacked up at the top end. Also reports around 650g/s which is around 85lb/min. Have a new fuel system in the works so don't hate on me.

[pannetron]

Isn't airflow in lb/min * 10 a rough indication of crankshaft HP?