VVE table warm vs cold ect

[boostslut]

E92 ecm. Doing vve tuning, maf disabled, 02s disabled.

When the engine is warm the vve error ratio is within 2-3%, fueling is good. When the engine is cold (30* F), the eq error is upwards of 20% for the vve table. Commanded fuel is lean (near stoich), wb reads lean, about 1.5 lambda.

So I figured since I'm forcing OL that the best way to do cold enrichment is to bump up the cold values in the OL eq ratio min vs ECT table (Fuel<OL base<Eq ratio min). It did command a richer afr (about .70 lambda) and now the wideband is about .85 lambda. Buuuut the vve table still had a 20% error ratio.

Obviously I plan on eventually enabling the 02s, CL, and Dynamic, but for the time being I'm working on the VVE.

Questions:

1. Is this the correct way to enrich cold starts in OL and SD?

2. Why didn't my vve error drop when I changed the OL eq ratio vs ect?

3. Is it normal for the vve error to be sky high when the engine is cold vs warm?

HALP.

[GHuggins]

Gen V's run an algorithm for temperature correction of the VE. I'm told that this algo is Sqrt(Tcharge/Tbase) courtesy of Verlon. That's about all I can help on the subject as I have yet to figure out a way to log square root in the scanner and nearly every truck I log is like what you're finding. 20% lean in closed loop while less than 30 degrees celcius then tapering to 10 or 12 % lean at 50ish celcius then more or less fine after that. I thought maybe fixing or correcting the base temp would fix it or at least make it better, but that doesn't seem to be the case.

If you trying to tune in open loop, which is the only time those open loop tables are in play, then you're really wasting your time. You're better off to tune in closed loop and correct things as needed.

[smokeshow]

Gen V's run an algorithm for temperature correction of the VE. [/FONT]

That goes back as far as Gen 3.

Cold engine fuel feedback isn't valuable info to calibrate the steady state airflow models. Engine must be warm.

[GHuggins]

That goes back as far as Gen 3.

Cold engine fuel feedback isn't valuable info to calibrate the steady state airflow models. Engine must be warm.

Is there any way at all to correct for it being leaner when cold? Even if the table isn't currently defined?

Right now I'm just running filters to ignore anything below a certain engine temp depending on the tstat used and outside of a certain injector tip temp range of 60 to 70 celcius.

[TheMechanic]

Educated guess but I think the +20 is just a default value. Similar to when a scan tool will enter data like a MAF reading even though it is not even connected. Likely that GM considered bad data from cold HO2S's and is dumping in a preprogrammed fuel volume that it believes will not lead to stalling (law suits). Not sure how to verify that as a fuel trim even with a wideband or a 5 gas.

[smokeshow]

Is there any way at all to correct for it being leaner when cold? Even if the table isn't currently defined?

Yes. Open loop enrichment.

[GHuggins]

Ivt table? And adjust independently of the regular open loop tables?

I've been adjusting just for open loop. Guess im doing that wrong

[smokeshow]

I mean...if you need to. There's a world of OL calibrations to be dialed in before engine reaches operating temperature... But none of them should inform the airflow models. That part should be done beforehand.

[GHuggins]

Hmm. I may have created my own problem in this case. I was checking on one of them I was seeing this problem on and I had changed the reference from engine load to map essentially putting the referenced cells up a couple of rows and higher numbers means leaner fueling..... Just being stupid and over complicating like usual. Changed it back to engine load and will find out on the next log if it changes it.

[DSteck]

Gen V's run an algorithm for temperature correction of the VE. I'm told that this algo is Sqrt(Tcharge/Tbase) courtesy of Verlon. That's about all I can help on the subject as I have yet to figure out a way to log square root in the scanner and nearly every truck I log is like what you're finding. 20% lean in closed loop while less than 30 degrees celcius then tapering to 10 or 12 % lean at 50ish celcius then more or less fine after that. I thought maybe fixing or correcting the base temp would fix it or at least make it better, but that doesn't seem to be the case.

If you trying to tune in open loop, which is the only time those open loop tables are in play, then you're really wasting your time. You're better off to tune in closed loop and correct things as needed.

You can 100% do square root in the scanner. Square root is the same as raising to the power of 0.5.

VE = VE * (Charge Temp / Reference Temp) ^ 0.5

Just make sure you're in Kelvin. The result of (Charge Temp / Reference Temp) ^ 0.5 gets stored to a variable that's available through a DMR if you don't want to calculate it in the scanner.

If you really want your mind blown... rpm is corrected too.

[GHuggins]

You can 100% do square root in the scanner. Square root is the same as raising to the power of 0.5.

VE = VE * (Charge Temp / Reference Temp) ^ 0.5

Just make sure you're in Kelvin. The result of (Charge Temp / Reference Temp) ^ 0.5 gets stored to a variable that's available through a DMR if you don't want to calculate it in the scanner.

If you really want your mind blown... rpm is corrected too.

Well SOB. I tried everything I could find for square root coding EXCEPT for that. Mainly cause I didn't think of it......

Yes, I want my mind blown. Educate me please!!!

I've got one right now driving me up a friggin wall. I can literally scroll through the log, watch VE airflow show under MAF airflow due to leaner issue when colder, then it'll do some sort of "reset/test" where the throttle blips and all of a sudden MAF and VE agree nearly 100% and it goes back to idling normally and ONLY has this issue with an overnight cold start idling for several minutes.

Thank You Dave and Jake!

[boostslut]

Gen V's run an algorithm for temperature correction of the VE. I'm told that this algo is Sqrt(Tcharge/Tbase) courtesy of Verlon. That's about all I can help on the subject as I have yet to figure out a way to log square root in the scanner and nearly every truck I log is like what you're finding. 20% lean in closed loop while less than 30 degrees celcius then tapering to 10 or 12 % lean at 50ish celcius then more or less fine after that. I thought maybe fixing or correcting the base temp would fix it or at least make it better, but that doesn't seem to be the case.

If you trying to tune in open loop, which is the only time those open loop tables are in play, then you're really wasting your time. You're better off to tune in closed loop and correct things as needed.

Ok you're speaking gibberish to me lol.

1. What is tcharge and tbase?

2. How can I tune off the wb in closed loop? I've always been under the impression that to tune from eq ration error I need to disable CL so that it doesn't apply trims while using the wb to dial things in. I get that I can update the vve table off fuel trims, but that does me no good when I get to PE tuning.

3. Why is it wasting time? When I changed the OL eq ratio min vs ect not only did it change my commanded it changed my actual afr.

In regards to this algorithm that runs for ve temp correction, if that can be logged how could that be applied to the ve so the ve is more in line with the proper airflow at colder temps?

[boostslut]

That goes back as far as Gen 3.

Cold engine fuel feedback isn't valuable info to calibrate the steady state airflow models. Engine must be warm.

Are you saying that the VVE table is going to be "off" when the engine is cold no matter what? It's normal?

[smokeshow]

There's nothing to really measure for the VE temp correction. The concept is that when air temperature changes, so does the speed of sound. And VE is dependent on the phase angle of the pressure waves that travel up and down the intake ports. So, you have a correction to compensate for the small deviation that occurs. The challenge is that this correction depends on charge temp, not intake temp. And getting manifold charge temperature accurate when you have intake system changes can be another beast altogether.

That said...a cold engine deals with many more complications aside from VE temp correction. So again, you should not be using cold engine data to do anything to the MAF or VE.

[boostslut]

Sooo, I just noticed under Airflow<Speed Density, there is Temp Corection. The base temp is set to 68*, and there is a EQ ratio multiplier table.

If I'm understanding this properly couldn't I just lower that 68* temp down to 0*, and adjust the multiplier tabel? The EQ ratio mult table will add airmass given a certain EQ ratio.

Or am I way off base here?

[boostslut]

So again, you should not be using cold engine data to do anything to the MAF or VE.

I'm not trying to change the MAF or VE to accomodate to cold air. In a warm state it's dialed in. I'm trying to use other tables and modifiers to change it while it's in a cold state. Maybe I'm just overthinking this and getting hung up on it.

[boostslut]

Wish I lived in Florida.

[smokeshow]

I'm not trying to change the MAF or VE to accomodate to cold air. In a warm state it's dialed in. I'm trying to use other tables and modifiers to change it while it's in a cold state. Maybe I'm just overthinking this and getting hung up on it.

Open loop enrichment is what you want.

[Alvin]

Another point in cold engine tuning is to understand only vaporized fuel will burn. A cold engine cannot vaporize fuel like a warm one can. So while cold the OL enrichment will target numbers much richer than stoich. This is so hopefully enough fuel was vaporized to burn normally. Bottom line you do not want to tune OL enrichment to match commanded AFR.

A example would be while cold commanding .85 at idle but wideband reads .96-1. That would be perfect.

[DSteck]

Another point in cold engine tuning is to understand only vaporized fuel will burn. A cold engine cannot vaporize fuel like a warm one can. So while cold the OL enrichment will target numbers much richer than stoich. This is so hopefully enough fuel was vaporized to burn normally. Bottom line you do not want to tune OL enrichment to match commanded AFR.

A example would be while cold commanding .85 at idle but wideband reads .96-1. That would be perfect.

The best example is that misfires read dead lean!