Spark IAT table and it's effect on spark tuning.
I see that the IAT table retards timing based on intake air temperatures, which explains why sometimes when I'm logging spark knock I don't get any and others I do. Should I just keep removing spark from the high octane table where I'm getting knock and retard and not worry about the changing conditions from the IAT table? It runs really well, just trying to do the right thing. I've attached my most recent files.
82 Corvette_0033.ctz
Log_0053.efi
Nothing? It seems like a valid question, if you have other spark tables like the IAT table and to a lesser degree the ECT table (which really only affects at lower engine temps) changing the amount of spark retard you're logging it would seem difficult to get a clean High Octane table. Ideally I would imagine you'd zero out any other tables that would change the amount of total timing and then with identical Hi and Low octane tables you would log spark retard and remove timing until you can drive under all conditions without spark retard. Then the next step would be modifiers like the IAT and ECT tables although I'd have no idea how much retard or advance to put into them. There are many different choices in different calibrations, in my case since my non stock motor seemed to run the best initially with a 2002 Corvette Hi Octane table I chose to use the other spark tables from that calibration. I also assembled a Hi Octane table that used the higher spark values from a number of different tables in areas of the table that I don't see while driving normally and used that as a starter table. After logging retard I've removed quite a bit of timing from that starter table and I'm sure I'll end up removing more when I tune on a dyno and hit some of the cells I can't get on the street. As it stands right now I think I'm pretty close under normal driving conditions but there are adjacent cells with a 4 degree difference and I'm sure it's from these other tables. I'm sure there's a logical approach to this that I haven't stumbled across in my google searches, surely one of you has thought about it?
I'm thinking it over... I'm comparing it to some stock files where the spark IAT table does not contribute.
What year/model is the donor car for your engine and PCM...?
Hi Joe, thanks for your reply! It's kind of a mixture, 383 LS6 short block and intake with ported 243 heads and a 1MB PCM from a 2007 Express van with the 12613248 OS and 12606602 Calibration. I've been thinking about this and under most operating conditions the IAT table only takes away spark and the ECT table only changes spark below and above normal fully warmed up temperatures (which is a good argument for logging spark only when fully warmed up), so unless other tables are coming into play maybe this is nothing to worry about. My Hi octane table looks about like it should when compared to OEM tables, and it runs very well so maybe I'm doing the right things.
When IAT gets high the probability of knock increases... so you can use the spark IAT table to avoid that... IAT is usually not that hot, except maybe in hot summer conditions... like you said, nothing to worry about.
~ posted by phone ~
Posting Permissions
Reply With Quote