So the latest $8D from Tunercat has this parameter in it. Anyone have an hints on what this does? It would appear that it somehow takes your final AE values (calculated from all the other AE parameter) and tailors it for the RPM you're at. Does a larger value equal larger AE pump shot? Or the other way around?

 

TTT for ya...

 

Maybe I asked a question that stumped everyone!

 

I would need to look through the hac again to be 100% but I'm pretty sure it slows down (smooths out) the TPS movement in the AE routine.
The AE routine uses the filtered value as the lookup table value instead of the direct reading.
Increasing the value would "probably" allow you to reach higher table values (TPS% axis) in less time.
Filtering would make the AE come in smoother by providing several AE additions of smaller table (movement) values locations, rather that dumping the highest table value at it all at once. I believe that is the 12 mSec loop.
The uses the amount of TPS% change in that 12 mSec loop, by taking the current TPS% reading and multiplying by the filter value and then uses the difference between the new reading and a stored old reading from the last execution. That is used as the TPS axis, AE lookup table value.

 

What I'm looking for in the end is a way to adjust AE on an RPM basis. Seems like they have tables for AE vs everything, except RPM.

 

What's nice about finally having correct injector constants and offsets is that tuning becomes a lot more predictable and consistent.

I revisited this AE filter coefficient to see if I could fine tune the AE based on RPM. The Miniram seems to like a lot of AE delivered very quickly at low throttle delta TPS's... as can be seen from the LT1 using up to 50% more AE at low delta TPS values. I also use a .40 on the AE delta TPS scale factor (not the PW scale factor). But this also seems to be only applicable on the off idle transition. When at speed, small delta TPS changes do not necessarily like that much AE. So what's good for off-idle can sometimes conflict with what's needed at higher rpms.

While the off idle trsnsition AFR is just right, the rich spike while at speed is noticeable, particularly when I go from cruising to WOT at midrange rpms... AFR will peg rich on the WB and there's a momentary bog.

In addition to having leaned out the AE at 50% delta-TPS (which I'm still playing around with), I've been raising the filter coefficient values for RPM valies above 1000 rpm and it seems to be working out well. It's bringing the AE AFR values in to where the throttle is becoming more crisp.

$8D Has the filter table set at .063 for all RPMs.

LT1 ($DA3) has only one filter value constant .141 that seems to apply to every rpm.

I'm currently at the .141 and it almost seems optimized... probably drive it around a little more and see if I need to go any higher on the values.

 

The calibration item you referenced is located at 0x56B (can't rely on descriptions because they're all different, but this one is the only RPM-based table that affects AE-TPS). It contains lag filtering factors. While quite complicated under the covers, bottom line, the smaller the factor in this table, the more quickly AE-TPS will be invoked or will remain invoked longer. That's its only purpose. In summary:
- A factor from the table is used to lag filter two TPS% values (current TPS% and that 6.25ms ago).
- Later, current TPS% is compared to the lag filtered value, which with a small factor more closely resembles the TPS% 6.25ms ago. This will result in a larger current-TPS%-to-lag-filtered-value difference. A larger factor will move the lag filtered value closer to the current TPS%, resulting in a smaller difference.
- If current TPS% exceeds the lag filtered value by more than 1.17%, AE-TPS will be invoked. So the farther the current TPS% is from the lag filtered value, the greater the difference and thus AE-TPS is more easily (quickly) invoked.

The issue is a bit more complicated if already in AE-TPS, but the same logic applies -- smaller table factor = can stay in AE-TPS longer. But "longer" and "smaller" are relative to very short time periods. These calculations/decision take place every 6.25ms (160 times a second).

Given all values are 0.063, it appears GM did not want AE-TPS to be RPM dependent or the factors would have been different. This is not uncommon as several tables in the $8d code have the same value for all entries. Perhaps they saw a need in testing/development but results later indicated otherwise. Changing these factors will cause AE-TPS to be RPM dependent.

 

That seems to contradict the results I"m getting... higher values = lower AFR readings during throttle transitions??

What seems to also affect the speed at which AE-TPS is invoked is the AE delta TPS scale factor constant (not the PW scale factor). Again, that's only based on my empirical observation... no idea what is in the code for that.

 

You are correct. Smaller, not larger factors cause AE-TPS to be more easily invoked. In my hasty code review, the lag filtered values were swapped in error. Thanks for your comment. The original Post #7 has been corrected.

 

Ah, ok, thanks. Nevertheless, I'm always impressed by how you guys read through this code stuff and break it down. This stuff goes way over my head usually...

I always have to figure this crap out the hard way

 

Decided to look at this but would never attempt to explain the usage as it would take a week. This factor (0x535 Scalar=12.5% default) is used in conjunction with two other AE TPS factors (0x534=PW Factor Scalar=12.5% default and 0x543=Pump Shot factor Table). All contribute to the calculation of the AE TPS PW which is based on current BPW and the change in TPS% in the past 6.25ms. Larger factors = more AE TPS PW. For example:
- Coolant temp = 200*F
- 6.25ms TPS% change =
----1.95% (barely > than the 1.17 threshold to invoke AE TPS), and
----13.3% (a somewhat small change when accelerating)
- 0x535 Scalar = 12.5% and 25.0%
BPW prior to AE TPS = 2.2ms
--0x535 Factor--------------12.5%---25.0%-------12.5%---25.0%
--6.25ms TPS % Change---1.95%---1.95%-------13.3%---13.3%
--AE TPS PW----------------1.00ms--1.54ms-------4.27ms--7.32ms (first pump shot)
--% change in AE TPS PW---------54%-------------------71%

BPW prior to AE TPS = 4.4ms (doubled)
--0x535 Factor--------------12.5%---25.0%-------12.5%---25.0%
--6.25ms TPS % Change---1.95%---1.95%-------13.3%---13.3%
--AE TPS PW----------------1.50ms--2.00ms-------2.35ms--3.65ms (first pump shot)
--% change in AE TPS PW---------35%--------------------55%

As can be seen:
- doubling the 0x535 factor always greatly increases the AE TPS PW
- larger changes in TPS % = larger AE TPS PW
- higher BPW before invoking AE TPS = smaller AE TPS PW

Changing the table more gently controls the desired result -- larger factors at lower % TPS changes, which can be scaled up and down.

 

I'm going to have to re-read this numerous times before it gets through my thick skull...