How does this table interact with the base coolant advance correction table bias in the constants table?

Thanks.

 

Nobody?

I tried doing a search but either I'm missing something or the answer simply isnt' there.

 

Table entry minus the bias value. That's how a bias works, it's subed off the whole lookup table. So if it's 25 in the table and your bias is 20 then the actual timing added by that table is 5 degrees. It's useful to have the area of the table that the engine spends most of it's time (thermostat temp) zeroed out. So if the bias is 20 you'd want 20 in all those cells. Keep in mind TunerCat and TunerPro 4.0 should be taking the bias values into account when they display them to you. I only use a bias value on the cts SA vs load vs temp table so I can take out a couple degrees if the engine gets too hot.
So if you're using TunerPro version 4.0 or TunerCat, the bias value might be 20 and the table values should all be below that, maybe even a couple negatives in the hot temps. The older version of TunerPro didn't have this bias because it was restricted to the ecu file format (old and outdated).

 

I used the ECM bench a bit to verify that both values do indeed affect the resultant timing (the table and the constant), so they are certainly both active.

So, here's my guess.

first, tunercat automatically aplies the "base coolant advance correction table bias" (abbreviating to "bias constant" here on out) to the "base cool. adv. correction vs. load vs. cool. temp" (abbreviating to "the table"). That is to say, when I view the table, most of the values have 0, a few positive, and a few negative. however, if I put a 0 into the bias constant, then all the values tunercat displays for the table are 20 higher. This was a clue...

Second clue is that, when the offset is applied, some values are positive, and some are negative in the table.

So my opinion is:

GM decided they wanted both postive and negative values for timing correction based on CTS and MAP. But on a 0-255 (8 bit) scale, there is no negative numbers, just positive. So, what they did is made the entire table have a value of "20" in every spot, then subtract off the bias value (which they also set to 20). The result is that you still have no net effect on the timing.. but suddenly the table now can effectively have negative numbers. The range of values 0 through 20 actually results in a timing reduction because (example) 15-20 = -5.

If for some reason you needed even more timing retard based on coolant/load, you could increment every value in the table by 10, and then also increase the bias value by 10. This would give you a further 10 degrees to work with (values from 0 to 30 with a bias of 30 subtracted off).

hope that helps, and that the experts correct me if i'm wrong.

edit: looks like jprevost beat me to the punch!

 

So does this mean if useing Tunercat and I have 30degrees
in the spark table and 10 degrees in the coolant comp table and
20 degrees Bias
then I would have 40 degrees advance or would I have 20 degrees advance

 

As displayed in tunercat (and as I understand it), you'd end up with:

30+10 = 40.

tunercat automatically includes the bias value when it displays the cool comp table on the screen. In other words, if the value on your screen is "10", then the actual value in the chip is "30" but tunercat has already subtracted off the bias for you.

 

40 degees because Tunercat displays the table WITH the bias. As a test, close all the windows and change the bias to 0, now look at the tables.

 

Does the coolant comp table effect
the timing at idle or only off Idle

 

Always, it has nothing to do with idle (in all the code that I've sifted through).

 

very interesting..but how does this table interact with e.g, main spark adv vs load....

thank you