WS6snake-eater

OK here is a test to see if your process worked. Use your VCM controls and set the car to open loop 13.0 AFR. Log with a wideband and see if your AFR is 13.0 across the range. Assuming that both the MAF and VE are good (we know the VE is good) then you should have a nice looking histogram. If the MAF is off at any point you will see it differ from the 13.0. FWIW it seems like the way you did it should work assuming that the VE is dead nuts on.

Matt

txhorns281

iTrader: (12)

Right on dude, to tell you the truth I'm not super super worried about the MAF since I've verifed its consistency with the VE... I'm just wondering more about that richness effect going on down low... it's annoying...

I know the VE is right
I know the MAF is right

So other than that gas sucking theory that could be messing up AFR verification, why is it doing that!?!?!?!? And the other thing that crosses my mind, is that if the gas sucking theory prevails, then when I've verified my VE table originally, could it be wrong? due to the wideband sensor being thrown off by false AFRs in my exhaust??? Even if so, I've verified at 13.0... you can see it... it should still output stoich when commanded, regardless of the gas sucking BS... unless something is different about fueling when commanding 13.0 or commanding stoich....

txhorns281

iTrader: (12)

Ok to make it easier on the eyes... here's what the issue comes down to:

-Open loop commanding 13.0, VE table verified perfectly
-Open loop commanding 14.628, VE verified mostly except low rpm, low MAP
-Cannot command 13.0 in closed loop cuz won't be accurate anyway
-Closed loop, commanding 14.628, trims verified except low rpm, low MAP

This is all in SD mode, so MAF is not a factor...

There has only been one theory so far, about gas sucking down into the exhaust, but then why would my VE be verfied when commanding 13.0???

WHY DOES THE VE BEHAVE STUPIDLY AT LOW RPM/LOW MAP WHEN ALL I DO IS COMMAND A DIFFERENT AFR??? Yaaaaaaarg!!!!

Bink

txhorns281- Is your timing holding up and what is your Eq Ratio in the low map and low RPM areas?? If the PCM thinks you're real lean (as seen with the Eq Ratio) then it will pull timing. Eq Ratio= Stoich/AFR.





Check this Thread

Monitor PID - SAE.FUELSYS
Monitor PID - GM.EQIVRATIO

WS6snake-eater

Bink are you refering to o2 switchpoints, and their corresponding error corrections when you say "Eq Ratio"?

Bink

No, not O2s...... I edited ...see above^^^.

You can actually monitor Eq Timing/Spark with EFILive's V7 FlashScan.

txhorns281

iTrader: (12)

I'm not sure what you mean by that eq Ratio... but comparing my timing tables before and after I re-engaged closed loop the timing looks like there is very very little variance... looky:

Timing, SD/Open loop operation commanding 13.0 AFR



Timing, Normal (w/ MAF)/Closed Loop operation commanding stoich AFR



If anything, timing is slightly more in the Closed Loop log and that would make me run leaner right? Not richer...

Bink

I can't tell from the g/cyl vs rpm histos.
Your AFR is not off by a huge amount. If you log Spark Advance/Timing, "SAE.FUELSYS" and "GM.EQIVRATIO" you will be able to see if the PCM is pulling timing due to a " too lean mixture". Don't follow the histogram - export the data and follow the data sets as the car/system transitions through the low RPM - low MAP areas. If the Timing advance suddenly drops and the Eq ratio is less than 1.00 then the PCM MAY be pulling timing - pushing the AFR rich.
The "FUELSYS" pid verifies closed/open loop.
I'm not saying this is the problem....just one more function of the PCM you can rule out. FWIW.

txhorns281

iTrader: (12)

I dunno what those PIDs coincide with in the HPT software

txhorns281

iTrader: (12)

OOOOOOOOOOOOOOk I think I'm finding the problem here...

it looks like the Computer is pulling timing from 2400 rpms and below.... I dunno where it's pulling this timing or why... but i played back my Spark histogram in super slow mode, and watched it populate showing "last logged values" and I noticed that where I see stupid trimming problems as seen earlier in this thread, the timing often is less than what is dictated in the HO table... OK ok ok... here what i need someone to do!

Take a look at my BIN file, and check out some of the settings in the Spark tables.... I have theories here that may support why I have a loss of timing down low...

DOWNLOAD ME!!! I HAVE ALL THE SECRETS YOU EVER WANTED TO KNOW ABOUT...

1.) The big kicker - My Base Spark and H/L Octane Spark tables aren't really close at all in lower rpms... I never touched either of these except when I added a few degrees from 1200 and below to help with some bucking so as far as I know they are stock... But if the computer is switching back and forth b/w the two then i can definitely see where it may have some confusion about richness vs leanness... These two tables should be close if not copies right?

2.) The Startup correction is only activated for about the first minute so the timing pull there is only temporary... any reason to disable this, seems it would be ok to leave it alone???

3.) Since I have removed my EGR system, can i zero out my EGR correction?

4.) ECT correction = should i mess with this??? Looks like it could pull some timing... since i normally run around 180 degrees F (~80 degrees C)

5.) Startup Idle Flare Control - WTF is this and what does it do??? It look like that would directly effect my Idle timing... what would trigger this pull in timing?

Please feel free to look at all the other timing and spark settings as I know what spark advance is and does, but have not really yet touched or played with any of the sprak parameters and have limited understanding as to how they effect vehicle operation... I think this may be the problem after all! Thanks everyone, let's crack this **** over the head...

Ok so if this is the probable cause, that would mean I'd need to get my spark settings all figured out and probably redo that portion of my VE table right??? Since the data i was using before hand could have been false due to non consistent conditions???

Me ---> <--- Stupid timing/richness ****

HumpinSS

iTrader: (1)

If I am not mistaken if you have made changes to your base spark table needs to be copied to the HO table at idle and vice versa

txhorns281

iTrader: (12)

Ok so you are saying that respective idle columns need to be aligned with each other in the HO and Base spark tables??? I played with Diablosport for a bit before I got HPT and I know they fiddled with low end timing a bit in the HO tables... But i don't know how much... from stock should those 2 tables be close?

Anyone else have any comments on my thoughts listed above?

txhorns281

iTrader: (12)

OK so here's what I think I'm gonna do... I'm fairly positive I've taken away all the corrections and timing pulls that could be effecting my VE... I'm going to try and log and hopefully get timing from only the Base and H/L Octane tables, but I also lined the two up degree for degree... This way timing will be completely consistent (with the exception of KR if present) and I can monitor AFR... Here's what I did:

-Disabled DFCO
-Zeroed out EGR correction (since i have no EGR)
-Zeroed out ECT correction at operating temps
-Zeroed out Idle Overspeed Spark Pull (If the Ve is accurate than idle overspeed shouldn't be a big issue right??? Idle overspeed is caused by surging???)
-Matched Base Spark and H/L Octane tables

Something else I was thinking about is that my Low Range LTFT Boundary vs RPM is set at 2500... So is it possible that the computer might see zero TPS, as idle condition below 2500??? If that's the case it looks like the idle overspeed table (which is now zeroed) would originally subtract 3-8 degrees of timing depending on how much over commanded idle rpm is (850 for me). Perhaps changing my LTFT Boundaries is part of the solution too... If anyone can help me come up with some good boundaries I'd much appreciate it! Time to go log and see....

Another_User

it looks like the Computer is pulling timing from 2400 rpms and below.... I dunno where it's pulling this timing or why... but i played back my Spark histogram in super slow mode, and watched it populate showing "last logged values" and I noticed that where I see stupid trimming problems as seen earlier in this thread, the timing often is less than what is dictated in the HO table... OK ok ok... here what i need someone to do!

I am starting to figure out why these weird spark things are happening. I have been posting some of it on HPTuners site.

1.) The big kicker - My Base Spark and H/L Octane Spark tables aren't really close at all in lower rpms... I never touched either of these except when I added a few degrees from 1200 and below to help with some bucking so as far as I know they are stock... But if the computer is switching back and forth b/w the two then i can definitely see where it may have some confusion about richness vs leanness... These two tables should be close if not copies right?

It shouldn't really make a big difference. Your car doesn't "jump" between the tables...it's more like it "coasts". You have a value that goes up as KR increases, and the PCM picks an average value between the two tables.

2.) The Startup correction is only activated for about the first minute so the timing pull there is only temporary... any reason to disable this, seems it would be ok to leave it alone???

I would leave it alone for now.

3.) Since I have removed my EGR system, can i zero out my EGR correction?

Yes. I always do that too...just in case.

4.) ECT correction = should i mess with this??? Looks like it could pull some timing... since i normally run around 180 degrees F (~80 degrees C)

Yes. I always do that. If you have a low-temp thermostat, that needs to go "bye bye" in the temps you operate at. Be careful and make sure you don't get any KR from it. I didn't, so I don't worry about it any more.

5.) Startup Idle Flare Control - WTF is this and what does it do??? It look like that would directly effect my Idle timing... what would trigger this pull in timing?

Leave it alone. I think it just pulls timing to keep your RPMs from jumping too crazy when you start you car. Regardless, it won't help you either.

Look more closely at the possibility your car is pulling spark at light throttle and decel because it think you are at idle. I wouldn't zero it out completely if I were you. Remember, this has to work when your car is trying to find idle.

txhorns281

iTrader: (12)

Might this have anything to do with LTFT Boundaries??? Well.. I guess not since it still does this in Open Loop... So why would my car "think" it's in idle???

Bink

It doesn't neccesarily have to think it's in idle. If the Eq Ratio is lean, or MAF is out of range, it may drop to the lowest available timing value. Usually the lowest timing value is your Idle/Park table.

Look at EFILive's site Under FlashScan .....a Thread related to "Reasons for a Good Scanner" (or something like that?).... they've identified 18 different spark tables.

There is also a GM State Pid specifically for Idle. FWIW.

Another_User

It sucks...my 98 PID doesn't work...HPTuners is going to look at it...probably my stupid OS again (not the first time). I am pretty sure about the idle thing. I actually logged this phenomena in action with and without the spark adjustment table disabled.

I think it has to do with some threshold (my opinion, TPS) that we can't control yet...but that is just my opinion.

txhorns281

iTrader: (12)

Bink, thank you for your info but seriously... I can't do anything about those PIDs (I don't think...) I'm running HP Tuners, not EFILive so if you can give me a hint or anyone as to what the equivalent is then that would be more helpful...

Another_User

Actually, we a lot of those PIDs now (but I suspect there are more to come). We definitely have the Idle Spark PID he was talking about. I just can't use mine because I have a 98 with a poopie OS.

txhorns281

iTrader: (12)

Soooo does this mean there's no effective way to counter this timing pull without sacrificing driveability???

I shut off all the corrections and tried to get everything set so it would run entirely off the H/L Octane tables and Base Tables and at least at commanding 13.0 the VE AFR looked spot on... But I had significant surging at idle and I had throttle hang above 20 mph... I did not try this commanding stoich b/c the driveability sucked ***...

So I've narrowed down at least a few things in this process...

1) The ECT correction doesn't relate to this problem in any significant way
2) The Idle Overspeed Spark Control does eliminate some of the timing pull, but makes the car surge at idle... (well at least for me and I am cammed)

I guess I'd have to test each correction factor one by one... Another thing, why would I not be "jumping" in b/w Base and H/L Octane tables??? If I'm going less that 40 mph and have less that 1% throttle it references the base table... beyond those thresholds it goes to H/L Octane... So if I'm driving around the city, or at a stop light it's using the Base table and in my case my respective base table columns are anywhere b/w 6-10 degrees less than the H/L Octane tables...

When i was building average AFRs to tune my VE table with, most of my driving was well above 40 mph so no matter what I was using the H/L Octane tables... meaning that if the computer sees less timing than the H/L tables (and it should since I could be moving less than 40 mph and off the throttle completely) it will essentially not spark all the fuel supplied and run rich, and show negative trimming or richer AFR... So Maybe the answer is to find an average b/w the Base and H/L tables that the VCM can cope with and tune the VE with that timing value that way if you run a little less timing, it may run rich but not too rich, and vice versa for lean...

And amongst all this horseshit... now my scanner's connection keeps getting interrupted... sheesh!