O2 sensor tuning with Headers

[GHuggins]

I see much better O2 and fuel trim correspondence Michael, just too much fuel being added and taken away - nearly a 1 point swing which still isn't as bad as some of the logs you've posted... I assume it was surging badly or something else?

I think HPT's descriptions are all more or less off in one way or another - I learned this very quickly looking at how efi describes a lot of these tables... Try the error table - multiply it by .2... THEN if the error more or less cures it, you can always go back to the .8 and 1.8 and try the error with it? Just may not have the best O2 readings... Not sure until you try? You can also try the lower integrator and higher proportional...

[Michael_D]

Yes, surging... Could feel it, and some misfire'ing going on like before as well. I already flashed a new cal to it with Error halved. I'll post a log this evening. Thanks.

[GHuggins]

Did the error change make it feel any better? Don't know in your case, but one last thing to try is to add about 30 to your ect injection timing table and see if 1800 feels any better

[Michael_D]

Haven't tested yet. Stinking rain has fouled my plans to test. I'll be sure to update with all my experiments.

I did spend more time looking my logs and have to agree with your assessment. The O2 curves with the increased proportional values are a lot smoother. Not as many jagged jumps and drops. That has to be a good thing, I think.

[topher455]

The car is running amazingly well below 2000 rpm now!! The car always ran well and had good drivability but I always noticed it having some difficulty transitioning off idle when the throttle was pressed and also the tip in with the converter locked was always a bit rough like the engine wasn't very efficient if that makes sense. I definitely feel like I got a lot of my oem type feel back to the car now!! That's saying something for a cammed, stalled, and blown car lol.

I will attach my before and after logs. I also had a M6 1le here to tune yesterday that just had headers put on and the o2 were lazy as hell. So I began making the same set of adjustments to it as with mine and the o2 patterns started tightening up. I couldn't finish it though since I noticed they cracked a plug during the install while I was working with the o2's. I really think the best way to mod these tables is to start by setting the rich lean switch point to 450 after the ect adder (or just use the settings in a zr1 cal) and then going over to the 16 or 24 airflow cell in both the prop and integrator tables and using that value all the way down to the 0 cell. That seems to be a quick way to start getting it in line. From there keep lowering the integrator delay to tighten the pattern in the airflow areas where the signal is lazy.

After these logs I actually pulled the integrator down more and made cells 0,8,16,and 24 the same. Will update after I evaluate the change.

[schpenxel]

Looks like I've got some catching up to do!

[sevinn]

Looks like I've got some catching up to do!

Same. Strange I haven't gotten any emails with updates to this thread. All this info is making me want to start from scratch...

[GHuggins]

I've got a gen 4 I'll be starting back on tomorrow - maybe I can get some of this O2 tuning sorted out on it before it blows up (already made 820 to the tire at 12 psi - had the ever loving hell abused out of it - owner is insisting on 16psi now and 850 to 900 on stock bottom end) - it did have some very minor surging that I pretty well got rid of before, so we'll see what's the best route on it???

[schpenxel]

Now that should get interesting

[JBZ]

Sorry i have not been on here in awhile guys...been absolutely underwater swamped at work lately and have 2 little kids so when i get to the house im swamped again...typing out this message in a drive through line lol.

So those higher values that i was so stoked about havent panned out as good as originally though. Really slow swings at lower rpms, not as responsive as i would like and at some airflow cells things seem to be better and other (mostly lower) it seems worse. So back to the drawing board, i have dropped everthing down by .8 % and in the 0 cell have gone back to stock values. I have left the error rate halved and that seems to be helping. Every day im taking a little more out of it getting closer to stock values. Ill report back tomorrow or saturday when i have 5 seconds of time to analyze the data.

[GHuggins]

The car is running amazingly well below 2000 rpm now!! The car always ran well and had good drivability but I always noticed it having some difficulty transitioning off idle when the throttle was pressed and also the tip in with the converter locked was always a bit rough like the engine wasn't very efficient if that makes sense. I definitely feel like I got a lot of my oem type feel back to the car now!! That's saying something for a cammed, stalled, and blown car lol.

I will attach my before and after logs. I also had a M6 1le here to tune yesterday that just had headers put on and the o2 were lazy as hell. So I began making the same set of adjustments to it as with mine and the o2 patterns started tightening up. I couldn't finish it though since I noticed they cracked a plug during the install while I was working with the o2's. I really think the best way to mod these tables is to start by setting the rich lean switch point to 450 after the ect adder (or just use the settings in a zr1 cal) and then going over to the 16 or 24 airflow cell in both the prop and integrator tables and using that value all the way down to the 0 cell. That seems to be a quick way to start getting it in line. From there keep lowering the integrator delay to tighten the pattern in the airflow areas where the signal is lazy.

After these logs I actually pulled the integrator down more and made cells 0,8,16,and 24 the same. Will update after I evaluate the change.

The ZR1 brings something into the equation that I hadn't even bothered to think about - airflow of the blower added to an otherwise originally naturally aspirated car... In my testing where I multiplied integrator and proportional by 1.95 - it was naturally aspirated, so the further down stream O2's and slightly better flowing head, cam and intake setup was all I had to compensate for... Those with blowers and especially big flowing blowers, will need to go much less with the numbers - faster flowing gasses through the exhaust system and all! JBZ, this might be why your having to dial yours way back now? The ZR1 with a 2.3l blower and slightly better flowing cam - otherwise pretty close to a lsa engine that has a 1.9l blower, uses much much less values for the O2 tables... It even uses less compensators for purge flow (another thing we aren't considering) and shifts the airflow mode table quite a bit to the left to put the engine into the lower O2 settings much much quicker...

Looks like we might have quite a bit more digging to do?

[barum]

I've reading old GM patents on the subject, some of them date back to 70's and early 80's. Here's one which may lay ground for later approach by GM. Some of the principles of the proportional and integral gains AND transfer delay are explained. I'm starting to think the correct term for the integrator delay would actually be transfer delay.

Here's another technical paper which has studied the true transfer delay when compared to a SAE paper. I took the mentioned 2003 6.0 Gen3 VE and did some calculations and will be posting them soon. The interesting point can be that the rpm may be the only really significant factor on transfer delay and the greater header volume with LT's has smaller effect on the delay than what we have been expecting.

[JBZ]

here is another good one I found just searching the web that I found interesting. it is in regards to a different PCM then we have but I think the way the I P E are controlled are probably still relevant.

ECM Proportional Control

Robert Rauscher
7/9/2000

Copyright 2000, Robert Rauscher, All Rights Reserved.

This is specific to the 747 ecm. However, the methods and madness
applies to many of the GM ecm's. (Use at your own risk, no guarantee
that any of this is correct, nor was it spell-checked!).


A) The PID controller term starts with the 'slow-filtered O2' sensor
value, and ends with the final calculated bpw.


B) The PID controller term always works in the opposite direction of
the immediate rich/lean O2 sensor reading.


C) The purpose of the PID controller term is twofold. First, it
is used to obtain the desired AFR quickly. Second, it is used to
maintain the switching of the O2 sensor about the desired AFR point.

The PID controller term starts with the O2 Error Term. This is the
amplitude of error, between the O2 sensor and the desired O2. This
value is used as a lookup index for the actual Proportional Error
Term.


Three tables define the desired O2 sensor upper and lower limits. These
limits are used to decide whether the O2 sensor is either: below, above,
or within the limit window. These are the error boundries.


The desired O2 Sensor tables are located at: 0x494, 0x499 and 0x49E. The
tables are indexed based on airflow, in gms/second, 0 - 64.


0x494: Mean R/L Threshold, used to determine (somehow), the direction,
(and speed?), of the O2 sensor. End result is a moving richer, or
moving leaner bit (L000E, b6, 0x40). Also used to determine the occurance
and an O2 x-count.


0x499: Rich O2 Threshold, used to define upper window boundry for
the O2 Error Term.


0x49E: Lean O2 Threshold, used to define lower window boundry for
the O2 Error Term.

The above table values are converted by: O2mv = TblVal * 4.34


The upper or lower boundry along with the current Filtered O2 Sensor
are used to calculate the O2 Error Value. This error value is then
used to lookup various proportional values. If the slow filtered O2
value is within the window, no proportional correction takes place
(prop term = 0).

When at idle, defined by L0002, b7 == 1, the above tables will have
a bias added to them. The effect is to lower the AFR for a more stable
idle. This value is located at: 0x2F7. (remember this one).

The flag at L0008, b1, (rich/lean) is set with a O2 sensor higher than
the upper window boundry. That bit is reset with an O2 sensor lower
than the lower window boundry.

If the O2 sensor is within the window, the bit is not changed.


D) Once the Slow Filtered Error Term is calculated, it is used as
a lookup index into the Proportional Gain table at: 0x4A8.

Another lookup is done for a Proportional Multiplier term, indexed
by airflow in gms/second, at: 0x4C7.

The two above terms are multiplied together, divided by 256 and
used as the adjustment to the INT term. If the O2 sensor is lean,
the prop term is added to the INT. If the O2 sensor is rich, the
prop term is subtracted from the INT term.

Of course, the INT term is then used for the BPW calculation.

The math:

PropTerm = (Gain 0x4A8[O2err] * FlowGain 0x4C7[gms/sec]) / 256.

This makes the FlowGain (@ 0x4C7), dictate a percentage of the Gain
table (@ 0x4A8). The end result will always be lower then the Gain term.


E) For the Proportional Duration, lookups are done using the same
indexes as the prop-gain. The Slow Filtered O2 Error Term is used as
a lookup index into the Proportional Duration table at: 0x4B5.

Another lookup is done for a Proportional Duration Offset term, indexed
by airflow in gms/second, at: 0x4C2.

The results of the lookups are added together for the Proportional
Duration Term.


F) The upper and lower R/L threshold tables can be used to move the
basic AFR. As they form the O2 Error Window, by raising the table values
toward the richer side, the overall engine AFR can be pushed toward
the rich side (lowered AFR).

This is important to understand, these three tables define the overall
AFR when in closed loop. The Proportional Term is always trying to
move the current O2 sensor toward these table boundries. The INT follows
the Proportional Term.


G) The value labeled 'stoich' needs to match the O2 sensor AFR switch
point. On the '747, this value is located at: 0x2AA. The value is 147,
for 14.7 AFR.


H) The Slow Filtered O2 Error Term is the delta of the current Slow
Filtered O2 value and the proper window boundry, upper or lower. This
term is then used to lookup the Proportional Gain Error from
table: 4A8. (See D above).

The lower window boundry is used to calculate the Error Term whenever
the O2 Sensor is below that value. The upper window boundry is used
whenever the O2 Sensor is above that value.


I) When in idle, the Proportional Gain and the Proportional Duration
use specific values for idle. The Prop Gain is at: 0x2F9, and the Prop
Duration is at: 0x2F8. These replace the table lookups at: 0x4C7 and
0x4B5, respectively.

For a rumpty-rump engine, it helps to set the idle Prop Term low,
this reduces/eliminates proportional action. This can have the effect
of smoothing the idle.


J) A Proportional Gain and Duration reset takes place whenever the
INT is reset. The most common cause of an INT reset, is the BLM 'cell
in use' changing. There is an option to have the INT reset on an accel
enrichment (pump shot). Location: 0x0006, b5, 0x20. Enable INT reset
on BLM change is located at: 0x0006, b4, 0x10. (set to 1 to enable
option for reset).

Other causes of an INT reset: DFCO, PE, open loop.


K) Movement of the INT takes place whenever the Slow Filtered O2 Error
Term exceeds four (4), and, the INT delay timer has expired.


Note: The PID part of all this is:

Proportional: This is the Proportional Gain Term described above.

Integral: This is the Proportional Duration mentioned above.

Derivative: The Proportional Gain Term and the Proportional
Duration are reset upon the O2 Sensor changing direction.

[topher455]

I have no modified the error table in my tune yet because I don't think we have a full understanding of how it works? Do we still think the description is wrong?

I still need to get another car that's na with headers to try the 02 settings from the zr1 on. They may only be suited to fi cars. Although my car is a centrifugal and they seem to work very well. I also have a car here with a big ci solid roller motor that im going to try this on. I suppose that will be the ultimate test...

[topher455]

Also one neat trick that Im sure may help if you log maf in hz like me.. Open the airflow mode, P, and I tables as well as your maf vs airflow table. Switch the units on the maf table to lb/hr and you can see what maf hz ranges equate to the correct airflow lb/hr. The lb/hr value will equate to a particular cell in the airflow mode, P, and I tables. Now you can target the areas you have o2 signal issues with and be sure you are modifying the correct cells.

[JBZ]

I have no modified the error table in my tune yet because I don't think we have a full understanding of how it works? Do we still think the description is wrong?

I still need to get another car that's na with headers to try the 02 settings from the zr1 on. They may only be suited to fi cars. Although my car is a centrifugal and they seem to work very well. I also have a car here with a big ci solid roller motor that im going to try this on. I suppose that will be the ultimate test...

I dropped these in last night and what Ghuggins mentioned for the purge ON/OFF and LTFT purge values. seem pretty good to me so far, but every time I say that it goes to shit on my next drive.

Also one neat trick that Im sure may help if you log maf in hz like me.. Open the airflow mode, P, and I tables as well as your maf vs airflow table. Switch the units on the maf table to lb/hr and you can see what maf hz ranges equate to the correct airflow lb/hr. The lb/hr value will equate to a particular cell in the airflow mode, P, and I tables. Now you can target the areas you have o2 signal issues with and be sure you are modifying the correct cells.

this is how I figured out to see what table it was pulling from and how I determined that airflow mode break down I post a while back where I drew the lines in there based on MAF LB/HR. you can see with the swing speeds exactly when it changes for the most part.

[GHuggins]

Not crossing my fingers at this point, but just confirmed that we've never had access to all of the O2 tables... Stupid me had HP add in the tables to a vehicle that has already left the shop, so can't test with it, but trying to get them added to one I've got in right now for testing... These tables just control the rich/lean thresholds for the O2's - nothing special - just hoping that tightening them up will help with the corrections and air fuel swings... This is a pic from the tune that I had them added to - still hoping that they can add in the set stoic switch point table, but we'll see?

Read through the above descriptions - think these and the stoic table might play an important role?

Of course they are under diagnostics, so they may just be settings for controlling dtc's?

[JBZ]

Ghuggins, if you dont mind...what are the ecm numbers on pre cat ones? Ill hit up hpt and see if i can get them added to my tune. Thank you in advance

Just a thought but this could be in my case whats setting the misfires off

[GHuggins]

Again - I don't know if these will do anything at all, but here they are...

Pre Cat O2's - Lean Threshold - 50570 / Rich Threshold - 50571
Post Cat O2's - Lean Threshold - 50572 / Rich Threshold - 50573

I'm also wondering if there isn't some sort of way to correctly calculate - if nothing else - the integrator delay table? After reading the experiment posted above, it would seem simple enough - in a manner of speaking that is - to somehow rig up a dummy switch to plug in-between an injector and it's corresponding connector, then kill the injector at different airflow levels and somehow or another average out the time to when the air pulse hit the O2 sensor from the time in which the misfire took place??? Don't know - probably way more complicated and time consuming than I'm giving it credit for?

[barum]

VE-table of the engine used in test I linked earlier:



Predicted transfer delay according to Kaidantzis et al. [1993] is calculated as follows:

Resulting transfer delay for the same engine:



Measured transfer delay (up to around 4000 rpm) by Wiens et al. [year unknown]:


As can be seen, the correlation to RPM is very similar between the two, but the correlation to MAP behaves quite the opposite in real world (which is intuitive if you think about it: More air & gas => more exhaust volume => higher travel speed => shorter transfer delay in time domain).


EDIT: Integrator delay used by the PCM:



The difference between the two (negative values mean the integrator delay selected by the PCM is too short):



Predicted transfer delay based on RPM only looks like this:


The effect of the exhaust part of the formula is slightly larger than that of intake but both behave similarly and are responsible for the odd behavior seen with increasing MAP. (What if one would use vacuum values instead of MAP, hmm...)


Expected mass air flow for the same engine:



Measured transfer delay per mass air flow (as GM is determining the integrator delay based on airflow mode which basically is scaled mass air flow):


The red rectangle represents the area which is commonly utilized in every day use while being in CL mode. As can be seen (the ratio is far from being constant), the raw mass air flow is not the best factor for selecting the correct transfer delay.

I'll see if I can make (easily enough) a corresponding table based on airflow mode to test whether it has a better correlation to transfer delay or not.