ULTM8Z

Today was way hotter than it's been in a long time... 110+ F...

Took the Camaro out to get some lunch and after about 10 min of driving all of a sudden the car felt like it lost 10-15 hp, throttle response took a nose dive etc.... I'm thinking "what the devil?"...

Of course AC is running hard too, so under hood temps are getting up there.

After a little investigation, I found that my MAT table had a typo in the 44C entry. I try to maintain a slope of 8 counts in the table (stock is 12, but I found that 8 produces more consistent results), but the 44C entry was off by 4 counts too lean. Soon as I corrected that, the power came right back.

Holy smokes... that's some serious sensitivity that such a seemingly small error can cause the car to fall on its face like that.

???

iTrader: (5)

just out of curiosity are you using it as the mat like the tpi had it or the open element in the air duct?


I still think not understanding the mat table is what pushed me to a different code. well that and the ve excel file code 59 had was really easy haha.

ULTM8Z

I run my IAT sensor out near the air filter that's outside the engine compartment to avoid heat soak. Gives me VERY consistent results in terms of fuel trims and seat of the pants feel across a wide range of air temps.

I then disabled the INV MAT table since the ECM's measurement of air temp is no longer influenced by coolant temperature (as it normally would be with the MAT sensor in the upper plenum). There's a switch that you activate or deactivate to turn on or off this table.

So my only MAT table to play with (for general fueling) is the MAT compensation counts table. There are start up fueling tables that look at the air temp, but I didn't really notice any difference on that.

ULTM8Z

My experience with 8D and the 7730 is that it seems like it's always "looking for an excuse" to lean out the mixture. In some other recent threads where I started playing around with some obscure coolant coefficients and stuff like that (which ultimately locked my BLMs to 128)... I think the title was "quasi-closed loop" or something like that...

It had a dramatic effect on the throttle response and general seat of the pants feel because it constrained the AFR's into the 13.5 to 14.5 range during part/moderate thorttle driving (rather than finding it drifting into the 15-16 range). It felt like it transformed the 7730 from a emissions oriented production ECM into more of a performance oriented ECM. I can still see the O2 and the INT making short term corrections, but it seems to keep the ECM going for more of a performance oriented AFR at all times (and ironically w/o much impact on fuel economy).

dabomb6608

iTrader: (3)

Ah the MAT/IAT...bane of my existence

My biggest gripes with tuning open loop has been the IAT and its effects on fueling. There are tons of threads about EBL and IAT but I have yet to find a clear explanation on what that table is doing to the fuel trim and how it is affecting it. Or how the readings of the IAT actually change the fuel trim. Similar to you, it seems like it all shifts the AFR leaner regardless of settings. It is almost like the fuel trim is going the wrong way as IAT raises, or there needs to be a "factor" to be able to have it increase its adjustment to the fuel trim.

With a bird cage sensor mounted in my elbow in front of throttle body. I have been meaning to extend the harness and move it up into my custom air box on drivers side battery box area where filter is. I constantly fight "heat soak". I can get the tune VE tables super close and the second I shut the car down to run in a store then come back out I start up to IAT readings above 115 and a lean fuel trim. Driving through town the IAT seems to never recover back towards ambient temps. Once above 45mph for extended periods it creeps back down.

Recently I raised my low Gr/Sec area of the IAT/CTS Comp Bias table, which shifts the bias towards CTS, before I flashed it in my faulty ECM situation happened. When I finally got my replacement and loaded that tune in I had forgot about that change. Started it up to find it idling 15-16 on cold start. VE table needed raised around idle to compensate. Haven't tested it at high IAT readings to see what it has done.

dabomb6608

iTrader: (3)

What I really need to do is just get my heated NB o2 installed and jump to closed loop tuning. My setup now that I solved all the mechanical issues it had over the years shouldn't be too hard at all to tune in closed loop. But I feel like I will still get bit by the IAT and would still need to solve that. But at least it would be able to self correct the lean shift...

ULTM8Z

Putting metal air temp sensor into a metal plenum has to be one of the dumbest things GM ever did IMO.

Until you get the air temp sensor out of the engine compartment and disable the IAT/CTS comp bias table, I wouldn't even bother with trying to tune it IMO. You'll be chasing your tail (as you're currently experiencing).

But after you do that, it becomes very easy to tune and you get very consistent results, using just the MAT Compensation Counts table (at least in 8D... I'm not sure what other tables the EBL has).

For example, on a particular day, I may be operating between two cells in the MAT CC table. Since the values in the table produce a line on a graph, I adjust those two cell values to get the right slope between those two cells such that the car operates consistently. Then on a warmer or colder day, I'd be between two other cells and tune the slope between those cells...

For 8D, GM has a slope of 12 counts per division, up to about 90C (194F), after which it goes constant out to 160C. However In DA3 (92-93 LT1), the slope varies from ~18 counts per divsion at the colder temps down to 8 counts at the higher temps, before going constant again at 90C like in 8D.

Though what's curious in DA3, is the LT1's actually had the IAT in the air tube, but GM still had the INV MAT table (effectively the CTS/IAT bias table) still activated. It probably goes to show that there is still heat soak occuring on the IAT as long as the sensor is in the engine compartment, and getting hot air from the radiator (effectively at coolant temperature) blowing over everything.

Any rate, yesterday I got into the 50C (122F) range, which for my setup is extremely unusual. I actually only took the car out to stress test the cooling system (which actually went really well), but then I uncovered the typo in my MAT table.

But over time I found that I found that a slope of 8 works better for me across the range of temps I usually encounter.

But I got the car dialed in at a particular air temp. Then as the air temps change and I'm operating in a different cell in the MAT CC Table, I simply adjust that value. It ls something you do need a WB for though so you can see the AFRs.

ULTM8Z

The thing is, I believe the IAT fuel corrections affects all synchronous fueling. So for instance in 8D, I believe the delta MAP AE is also delivered on synchronous fueling (as opposed to delta TPS AE, which is asynchronous). So the NB corrections may not fully compensate for everything. If the AE is off, the throttle will still feel laggy (which is also what happened to me).

dabomb6608

iTrader: (3)

The EBL has very limited IAT parameters. There are three that I know of.

IAT/CTS - Blend Filter
SA - IAT/CTS Compensation
SA - IAT/CTS Compensation Bias SA

I have the SA Parameters basically zero'd for no changes to SA to occur.

My Blend Filter is currently setup as shown below.



Beyond those three parameters there is nothing to adjust its amount of change placed on the fueling.

ULTM8Z

hmmm.... yeah...

I suppose on the fueling table for IAT/CTS comp, setting everything to zero you'd probably get the same effect as disabling it (once you move the IAT out of the engine compartment). Or at least have very low values comparable to the values at WOT.

The only thing is there's no other table that relates air density to fueling changes. Is this a MAF system? Maybe it doesn't need that information since it's measuring airflow directly.

On a MAP system, the ECM needs to be able to make a calculation on expected air density via that table.

dabomb6608

iTrader: (3)

MAP System. I would imagine 0 would use only IAT value. There must be some predetermined factor that takes whatever value is calculated from this table and puts it through an equation that then translates to a fueling change. What that factor or calculation is, is beyond me.

ULTM8Z

Yeah it seems like there has to be some air density vs temperature calculation being made somewhere.

In 8D, having two tables is too many variables and got frustrating trying to dial them in. After I disabled the INV MAT table, it made the tuning much more straightforward.

???

iTrader: (5)

grams/sec is what I'm used to seeing maf air flow measured in. that table probably made since when it was maf since you could log it directly. being map in guessing it's using map valve and math to come up with the airflow.

I always wondered if I should have went back to the stock big brass manifold temp sensor and just used the stock settings. wonder if that might be a thing to try if you have the original sensor laying around still and your intake has the port?

ULTM8Z

RBob could probably set us straight here. Strange that he seems to have just disappeared.. hope he's ok.

???

iTrader: (5)

Yes. I haven't seen any posts in a while. hope he's just doing other stuff and it's not something health related.

???

iTrader: (5)

I wonder if looking for how they tune iat in the 808 map code that runs on the 165 ecm in Australia might tell how it works. I don't remember the message board I found years ago, but they seemed to have that code really sorted out and documented. it was map I believe. it wouldn't surprise me if elb has some similarities go that air flow math wise.

BHR

What are you using for your count table, is your IAT in front of the radiator? would it be better to mount at the end of the air cleaner or closer to the TB

ULTM8Z

Here's what I ended up with. Where I live, the air temp will never get below 10C and probably never higher than 50C (it got up over 45C the other day when it was over 100C outside).

My IAT sensor is in the snout of a conical air filter that's mounted under where the battery used to be. Basically hanging down in front of the passenger side front tire.

BHR

gonna try this today along with the things you mention in Quasi-Closed loop thread, but for the MAT table mention here more counts is leaner or richer

ULTM8Z

More counts is leaner. Which kinda makes sense... the higher the temperature, the lower the air density, and the less fuel required to meet stoich.

On the quasi closed loop thing... you should make sure your BLM's are very close to 128 ahead of time. I'm not sure what'll happen if your BLMs are swinging wildly and then this modification locks the BLMs to 128.

BHR

yeah. you can feel a difference didn't have my laptop to log but it felt better, I was using the table I think elky posted years ago for the coolant/mat differential factor vs airflow table

my blms were ok before I dont know how tight you guys get them but mine where at a point where changes wouldnt help so i stopped playing with the VE I do swing to mid 130s and 110s but only if im doing abnormal things with the throttle

ULTM8Z

Great.

I think you'll get more bang for the buck too if you take the MAT sensor out of the plenum, get a true IAT sensor and get it in front of the radiator somehow, then disable the INV MAT table (which is essentially the MAT/CTS coolant bias table).

I had my BLMs pretty much between 124 and 132.

ULTM8Z

The other really important thing to keep in mind about my MAT Compensation Counts table...

I started with the DA3 LT1 MAT CC table a long time ago because they had the bird-cage sensor in the air duct like mine. In terms of absolute values between DA3 and 8D, the DA3 are significantly leaner. However, I was also using all of the DA3 AE fueling tables, so it all seemed to play very well together. So the only other things I had to dial in were VE, OL, and PE.

So I then did my baseline tune near for those around the 20C temp row, and I tuned the slope from there (at higher/lower temps) to find out that a slope of 8 was ideal for the overall curve. So the main take away from my MAT CC table is the slope, not necessarily the absolute values.

The MAT values in the factory 8D tables are meant to work with the rest of the fueling in the VE tables, OL, PE, AE, etc. Simply taking my MAT CC table values and dumping them into your calibration may or may not have the same effect. You seem to have had positive results.

Alternatively, if your car runs fairly well with your MAT CC table what you could do is tune around a particular temperature in your existing MAT CC table, and then try my slope of 8 from that temperature going colder and warmer. It may actually produce even better results.

Again, if you dump my MAT CC values in (given how different they are than factory 8D), you may have to go back and tweak other fueling tables (though I guess you'll find out when you start datalogging).

BHR

yes I had it in the plenum right before this with the stock tables, I also had it outside with elkys table, Im leaving it out for good now just wanted to see how much far off your table is vs stock tunes

Im using alot of DA3 in my bin aswell, what are your thoughts on Reset int to 128 when in AE, I have this checked off and In pe-dont add fuel based on blm entry, I have this unchecked which adds a pump shot

Here is the sensor its right at the edge of the intake track in front of the radiator

ULTM8Z

Yes, Reset INT when AE active.... I have that enabled. Did that a long time ago when I found DA3 had it enabled as well. I didn't want the ECM trimming fuel based on AE fueling.

I also disabled PE add fuel based on BLM.

I've said it before... I'm astounded how perfectly the DA3 values ported over to 8D, literally one for one, and how well it works with the Miniram. I would have NEVER gotten the Miniram running as well as it does if wasn't able to leverage GM's R&D on the 4th gen LT1s. It's almost like they run off the same basic code, despite the ECM/PCM's being different.

BHR

How do you see that DA3 has Reset INT when AE active using tuner pro I dont see this, I noticed you are using another SW tuner cat? does it show more parameters

ULTM8Z

Oh.... yeah, you need Tunercat to see it. See below.

TC has some stuff that TP doesn't have, and vise versa. That's why I use both. Essentially need both to really dive into the weeds.

Note how they also have the INV MAT table enabled even though the air sensor is in the air tube (albeit right in front of the throttle body). Makes me wonder if GM was still trying to account for some heat soak even with the IAT in the air tube, due to hot air blowing from the radiator.

Matter of fact if you look at the INV MAT tables between AUJP and a couple of DA3's (LT1 A4 TransAm and 6-speed Camaro)... you can see that GM didn't compensate for coolant temp nearly as much at very low air flows. At high airflows where air speeds are very high, as expected, coolant temp plays a much smaller role, so they all tend to converge to a similar value. Although counterintuitively, AUJP's gets to the minimum value faster.

Any rate... The tables aren't too tough to understand once you start thinking about the physics behind them.

Street Lethal

iTrader: (16)

We tune this area similarly to how we would tune AE using a blending of both the MAP and TPS for acceleration enrichment, where most tuners if not all rarely even use the MAP side and would just zero out the MAP values and just set the TPS AE trigger points. I'm assuming he did this in relation with the IAT/CTS to allow the user to refine the tuning and make the overall feel of the engine smooth in varying transitions using feedback from both areas, but from what I see in the calibrations the values are set to 9.84 which negates any changes being made either way. The blend filter appears to have predetermined values entered, but those are the proper values based on airflow vs blended CTS/IAT if you decide to do it, similar to the way he added the boosted values giving the user the proper starting point if he decides to go that route. Also please be aware that the blending and parameters found in these three locations have to do with spark advance and not fueling...

Guys, he's only been away for a little over a month, give him time.

- Rob

ULTM8Z

105F out today.... Took the car out to check for consistency, and yep... still very consistent with the slope of 8 counts per division. It rarely gets this hot over here, so it was a great opportunity to check the higher temps in the MAT table.

dabomb6608

iTrader: (3)

I can say fairly confidently that the blend table has an affect on fueling as well as the SA IAT Comps. It significantly leaned out my idle/low rpm area during warm up and at running temps when I added ~ 10% to the lower GmSec area. Prior to that change I hadn't had issues with lean AFRs during warm up.

Street Lethal

iTrader: (16)

Looking at the XDF I do not see how it could be possible. As pointed out, the IAT is only prevalent in three specific areas in the XDF. However the title of these areas perhaps best explains the method to his madness. Lets look at them quickly...;

SA - IAT/CTS or IAT Compensation (the or perhaps indicates it is exclusively for the IAT, especially considering the area found just before this table in the XDF is the SA Coolant Compensation table, exclusively for the CTS)...

SA - IAT/CTS Coolant Bias (both the IAT Compensation and Coolant Compensation have a 9.84 bias)...

IAT/CTS Blend Filter (looking at the two columns we see Air Flow and %ofCTS, no mention of IAT)...

So, if one were to zero out or change the values from 9.84 in the IAT compensation table, this will either add to or subtract from the final spark advance at a given temperature using the CTS, which of course has an impact on the air/fuel ratio at that temperature. So looking at the way it is setup in the XDF, I'm observing...;

SA Main Table > SA Coolant Comp > SA IAT Comp > IAT/CTS Blend Filter > Final Spark Advance...

But again, Bob left the SA IAT Compensation at 9.84 having zero change. He only has the SA Coolant Compensation changing the spark advance based on coolant temperature, adding more down low, adding less up top. It appears he had left the IAT compensation "open" and at zero (9.84) if someone wanted to include it in the equation. So the question in your case is, did you zero out or change the IAT Compensation table from 9.84 (zero) anywhere in that table...?

- Rob

dabomb6608

iTrader: (3)

The supplied XDF is lacking. I have actually modified my XDF to include definitions for all terms as found in the EBL Calibration file. Saves me from having to go back and forth.

Looking at the EBL Calibration file supplied with the EBL there is a section which states:

Blend Factor for CTS and IAT
The code has the functionality to blend together the intake air temperature and the engine coolant temperature. This value is then used for various fueling functions. The inverse temperature term of the gas law for the PW calculation being primary.

It is designed to take into account the heating of the intake air as it passes through the engine. At low air flows there is more heat picked up by the air stream. At higher air flows the air will not pick up as much heat.

• Entry: IAT/CTS - Blend Filter

A table defining the amount of CTS versus IAT value that makes up the final IAT/CTS value. A larger value has the CTS making more of a contribution.



You can also check the following found under Option Word 6. Note that mine is not checked.:

ICbAE - set to use the IAT/CTS blended temperature term for AE & DE compensation, else use CTS



Regarding the SA comp this is listed:

SA - IAT/CTS Comp Bias SA

Bias value for the CTS/IAT blended spark advance table.

SA - Coolant Comp Bias SA

Bias value for the Coolant Compensation spark advance table.

Those two tables act on each other. Using (I assume) the blended IAT/CTS value created by the IAT/CTS Blend Filter. Mine still has 9.84 in all values as to zero each other out with no change to SA being made.

ULTM8Z

Out of curiosity... is there any IAT compensation for spark advance in $8D? I don't see anything like that in Tunercat or Tunerpro. But maybe I'm missing something???

Street Lethal

iTrader: (16)

Yeah I get what you're saying, but the values being used from the IAT feedback is in a 9.84 bias form, and this is exclusively for spark advance. I don't see anywhere in the XDF that indicates fueling is affected by MAT/IAT feedback. Even the enabling/disabling of the sensor itself (Option Word 4 - Bit 4 - IatSa) is expressed as, and in relation with, Spark Advance. Could be possible it is hard coded in the firmware, but then again the user him or herself being able to disable the sensor and remove it from the loop, I don't see how that's possible. Also remember that these V8's came with a heat soaking MAT sensor unlike the V6 models, so I don't see Bob giving supplemental fueling control to a MAT sensor. I'm sure he'll clarify when he comes back...

Edit - But the key acronym here is IAT, something these engines did not come with. Just like boost. I always tune this field as an "add on" because Bob left it at 9.84 (zero), and in my case, running high boost, I needed to add the birdcage IAT sensor for better accuracy and allow for added spark advance retarding when intake temps were getting too high under boost pressure...

- Rob

dabomb6608

iTrader: (3)

Not trying to be rude here but it doesn't matter what the XDF says. His documentation directly states "The code has the functionality to blend together the intake air temperature and the engine coolant temperature. This value is then used for various fueling functions. The inverse temperature term of the gas law for the PW calculation being primary."

So the code is blending the IAT (call it MAT if you want) and the CTS values into a single value and then using it to modify various fueling calculations. Specifically, directly affecting PW calcs. My original complaint is the "how" for those modification hasn't really ever been discussed in depth (that I have found).

It is being called IAT in the documentation regardless of where the sensor is located. Nowhere in the documentation is it referred to as a MAT. Including the wiring diagrams.

Also, for EBL Flash (what I have), Option Word 4 - Bit 4 is not used and labeled "Option Word 4 - Bit 4 - N/U. There isn't a option word anywhere in the documentation that "disables" the IAT. Least not one I see.

Street Lethal

iTrader: (16)

I never consider a good discussion as being rude, so speak freely. Your EBL Flash may in fact have it hard coded in the firmware then if you are unable to disable the sensor, but I doubt it. Let me take a look at your XDF real quickly to see what's going on, as I have to admit I assumed you were running the EBL P4. Also, the original sensor is called a MAT, never seen a TPI come with an IAT sensor. I don't believe the TBI engines even came with a MAT/IAT sensor for the record as well, and these systems were exclusively created for these vehicles...

Hold on...

Edit: Is this your XDF below? It's there from what I can see, and all it does is enable or disable supplemental IAT SA, which it isn't even enabled in the calibration from the getgo looking at various stock calibrations that the system comes with. So again, if the system has it hard coded in the firmware using the MAT/IAT feedback as part of fueling control, then this is something that Bob will have to confirm because the XDF embellishes no such thing. What the XDF does show is the IAT, which is not even active because its both unchecked as well as pre-set to 9.84 which negates any changes being made, being supplemental spark advance control. That is all those three areas demonstrate. If you altered the IAT Compensation from 9.84, and enabled it, then there should be no surprise that the air/fuel was effected in a certain area because the timing was...

- Rob

drive it

iTrader: (1)

Blend Factor for CTS and IAT
"The code has the functionality to blend together the intake air temperature and the engine coolant temperature. This value is then used for various fueling functions. The inverse temperature term of the gas law for the PW calculation being primary.

It is designed to take into account the heating of the intake air as it passes through the engine. At low air flows there is more heat picked up by the air stream. At higher air flows the air will not pick up as much heat."
(IAT/CTS blend filter)

This is from the EBL P4 Calibration help file. In flags there is an option to use IAT for spark only (Opt word 4 bit4) I have mine unchecked, so it is supposed to use it for fueling also. . On one of BobR's posts he had a suggested for the IAT/CTS blend filter. depending on where the IAT is placed. Since I have a birdcage style in the plenum and it is SC with an intercooler I changed to his suggested for that situation which is heavily biased to the CTS-at 0 airflow it's 100% CTS and at 255 airflow it's 70% CTS. This has worked out well for me.

Street Lethal

iTrader: (16)

... it's supplemental spark advance control, but it's supposed to be used in the fueling calculation then, so this would indicate that it is in fact hard coded into the system being that the fueling portion cannot be altered. I use mine in the very same manner, enabled and supplemental. Good job.

- Rob

???

iTrader: (5)

the ebl flash being a tbi ecm and maybe code first and port mod added, I think is playing into this. if I remember right some of the first tbi codes didn't even have intake manifold Temps.

the P4 code I believe is more like 8d, especially since it a used a 730 ecm as it's base. wouldn't supised me if it was handled a totally different way.

dabomb6608

iTrader: (3)

I haven't touched the two SA IAT Comp tables. They are at 9.84. I am not denying what those two parameters do. I think the confusion is that the IAT/CTS Blend Factor appears to be used for those two tables plus whatever hardcoding is happening in the background for fueling adjustments.

Here is my XDF and the available option words.

Just looked at a datalog and I am running firmware 2.4. Looks like latest is 2.7.

Here are the changes per the website.

03/01/22 V2.7 Current Version

• Fixed delta MAP AE when async dTPS is in affect
• Changed digi-dash ALDL to prevent upshift light on some Y-Body cars during idle

09/01/18 V2.6

• Changed N2O to be progessive (instead of on/off)

08/15/14 V2.5

• Added option flag (LD007b, b4) for IAT/CTS SA compensation, with flag set that table is only based on the IAT