I ran several datalogs doing WOT 1-2 and 2-3 shifts with 87 octane (I run 87 octane almost all the time with the SHO) and see that it pulls a max of about 7 degrees of timing at certain cells, but that happens to be about the max amount of timing the computer is supposed to pull based on detected knock. I ran the tank almost empty, and filled it with fresh 93 octane (based on the 19 gal capacity, I calculate about 80% of the fuel in the tank is 93 oct), and ran the same test scenario but at a colder ambient temperature (I blame Michigan's crazy weather).
Even with the stock tune, it's pulling on average 2-3* timing at the high RPM/high load areas, and a peak of 4*-5*. Should I reduce these values in their respective cells or just let the knock sensor do its thing?
I also added a snapshot of the WOT run from this morning with 93 octane fuel. The trans temp is scaled wrong, and HPTuners is going to fix it in the next release. It's displaying numbers in *Celsius, but with the units in *Fahrenheit. I also know my throttle pedal was jammed to the floor for the entire run, and can see that the computer limited the throttle angle opening. It looks like the Combustion Stability Limit table might be the cause for the torque limiting, but I'd have to experiment in the future. And the boost value in the graph below accounts for the atmospheric barometric pressure so it's not an absolute number. I saw a peak of 11.4 psi, but it holds steady at around 10 psi (at around 4500 RPM / 140-150% load based on the boost table I have up there).
The fuel trims are still jacked up though, I'm seeing about +13% to +15%. Normally with a MAF system, I'd try to fix it right away and get it within 5% but I haven't the slightest clue where to begin on this speed density system.
So any ideas on the timing being pulled even with 93 octane fuel? Do I want to use one of those OTC octane boosters at the track? Or should I change the spark tables and pull a few degrees in those cells? I recall a long time ago that you don't want to depend on the knock sensors because it can pull too much spark and do it at the wrong rate. I have a mod plan already in place, but I have to figure out what to do with the car in the next 6 months or so (buy out the lease or get a 2017 SHO if they will be made)
