16 Sierra not responding to timing changes?

[Kallibrated]

Hi guys.

2016 Sierra, non-flex fuel model with sensor added. Ethanol is confirmed at 70% according to ECU.

The truck responds to all changes I've made in the ECU so far, but seems to run whatever it wants in the timing department. I've gone over the spark correction tables and what not, but It's just not responding to raising the flex fuel spark table. Whether I target 20* or 24* at redline, It would run 18.5* over and over, pretty consistently on the dyno.

I'm not able to watch knock retard on VCM scanner (not sure why, but bill is working on it with me).

Tried adjusting:

MBT alcohol adder
Peak torque settings
Confirmed IAT and ECT are not affecting me at these temps

I haven't experienced this issue on any other GM ecu. Any insight is GREATLY appreciated.

[Higgs Boson]

put all torque model to stock
put all spark tables to stock (leave the temp modifiers as 0 in the temps you are testing/running)
put the MBT tables all to stock

log your maximum cylinder airmass at WOT, maybe it will be .76 or .80 or something....

set three rows lower than max all the way to the bottom of the table to 20 degrees from 2500 RPM to redline, copy the high table to the low table.

check your VVT spark table to make sure it is zero'd out at WOT (at least for testing).

set your Flex Fuel Spark modifier table to 5 degrees from 2500 and up in the same cylinder airmass rows as your 20 degrees cells in your main spark tables

now see where your spark is at wot.....should be around 23-24.

if not, check all your TM tab settings, trans TM settings, etc for things that are not max'd out and could be pulling spark, also check your Accel Thresh table in the Limiters section of fueling where your rev limit settings are, should be 0'd out.

[Kallibrated]

put all torque model to stock
put all spark tables to stock (leave the temp modifiers as 0 in the temps you are testing/running)
put the MBT tables all to stock

log your maximum cylinder airmass at WOT, maybe it will be .76 or .80 or something....

set three rows lower than max all the way to the bottom of the table to 20 degrees from 2500 RPM to redline, copy the high table to the low table.

check your VVT spark table to make sure it is zero'd out at WOT (at least for testing).

set your Flex Fuel Spark modifier table to 5 degrees from 2500 and up in the same cylinder airmass rows as your 20 degrees cells in your main spark tables

now see where your spark is at wot.....should be around 23-24.

if not, check all your TM tab settings, trans TM settings, etc for things that are not max'd out and could be pulling spark, also check your Accel Thresh table in the Limiters section of fueling where your rev limit settings are, should be 0'd out.

Thanks Higgs!
I will try all of this from a troubleshooting standpoint, but I like the idea of a stock high/low oct table (for 87 fill ups) and maximum power on E85 by modifying the flex spark only. Does that typically not produce my intended results?

[Higgs Boson]

Thanks Higgs!
I will try all of this from a troubleshooting standpoint, but I like the idea of a stock high/low oct table (for 87 fill ups) and maximum power on E85 by modifying the flex spark only. Does that typically not produce my intended results?

Tune your spark with the tables matching then when you are done you can lop 10 or so degrees off the low octane table to accommodate octane/fuel issues. Sometimes after I tune spark I will add 5 to the end results high map, copy it to the low map and subtract 10-15 degrees from it so spark has a little room to move up and a lot to move down. Really, it's up to you and the application.