Originally Posted by
Kill
Alright, since this was touched on in another thread I figured I would share what I have been messing with for a while. I haven't been able to test every table, but from what I have found all of the tables labeled "Adder" in the editor for early 04 trucks are actually either minimum or maximum value limiters to the corresponding base table. I have mostly messed around with the rail pressure tables so I will use those as an example.
It had been bugging me that my rail pressure values in my logs never seemed to match my base table except for basically wide open throttle. So I started messing with the ECTxIAT adder table. I attempted to disable it by setting the coefficients to zero. The result was a truck that would start hard and barely ran. Not what you would expect to happen with the current labels. So since zero didn't do what I wanted, I went and tried the max coefficient found in the table, which was 5. Voila, rail pressure from my logs now matched my base table perfectly. But why? To try and figure out how this was all working , I put the coefficient table back to stock and zeroed out the adder table. Had the same result as when I zeroed out the coefficient table. I'll skip some in between steps here as I tried flattening out the adder table with a few different values, but the coefficient table was skipping around making my data inconsistent.
It was about this time that I formed a theory, so I set the coefficient table to one and and started playing with the adder table again. I set the entire adder table to three and the truck would barely run with rail pressure only staying between 29-31 MPa, so I upped it to 4 and tried again. Truck started fine, idled normal but rail pressure on a drive only varied between 37-39 MPa. Next test was to set the adder table to 10 and try again, the result was rail pressure that would follow the base map up to a max value of 98 MPa. Setting the table to 20 allowed rail pressure to follow the base table almost perfectly everywhere once again. Now you probably noticed a pattern here, values of 3, 4, and 10 in the adder table with a coefficient of one equaled a limit of approximately 30 MPa, 40 MPa, and 100 MPa. Which means 20 would equal 200 MPa and be higher than any value on the base map removing all limiting. So if this table really is in MPa, another digit needs to be tacked on to everything in the software.
All of this led me to the conclusion that the adder tables for rail pressure were a maximum limiting table, so I started applying this to other tables in the editor. However, if you look at the coefficient modifiers for most of the other tables in the tune they are set to 0 in the normal operating temp range. This leads to the conclusion that these are minimum value limiting tables and not maximum value limiting. I believe the only other max limiting table besides the ones for rail pressure is the ECTxIAT Pilot Timing table.
I have been following this theory, and so far it seems to hold water for my truck. The only times I haven't been able to get the truck to do what I want it to is when I hit misfire minimum timing, which affects the main timing and there also seems to be something else that affects the maximum pilot timing allowed as well. Keep in mind this is all on an early 04 truck, I haven't had the chance to test it on anything else. I'm looking forward to seeing if all of this correlates to what other people have been seeing.
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