Delayed FA Enrichment = Misfires?

[Stoopalini]

2023 Dodge Durango R/T 5.7L with Gen 5x Whipple 3.0L Supercharger with a 92mm Hellcat Throttle Body

Looking through a log from my latest iteration of the tune, I am noticing misfires being logged during a time where I think PE should be coming on but FA Enrichment still tracks 0 for a time.

Here's a screenshot from the log I attached below, where I would expect FA Enrichment to start, but notice in the channel listing it still tracks 0.

Throttle-event-start.JPG


Here is where FA Enrich starts increasing, but the misfires have already happened now:

Throttle-event-FA-Enrich-Start.JPG


During the remainder of the throttle event, no further misfires occur and PE seems stable:

Throttle-event-FA-Enrich-End.JPG


As far as I can tell, Pedal Volts, PRatio, RPM, Aircharge, etc ... are all over the thresholds for PE to begin before the misfires happen and I'm not sure what is delaying it. Any ideas on where to look would be appreciated.

Latest tune file: Latest_Tune.hpt

Log from this file: Last_Log.hpl

And just for good measure, here is the stock tune file: Mar24_2024-0307PM.hpt


I've been chasing some odd issues with this tune, and recently swapped the 80mm throttle body out for a 92mm Hellcat throttle body. After doing so, I modified the TB Airflow table, as well as the Small and Large range tables. This seems to have resolved the unpredictable behavior I was seeing with the 80mm TB. I believe a previous tuner compensated for the issues we were seeing by adjusting the AFR target and VE tables, and now with the Hellcat throttle body, I think it is probably running too rich at WOT now. I'm sure I need to address that, but the immediate concern is the misfire counts during a time when it seems PE should be coming on and preventing them.

[smokeshow]

Reduce WOT pedal thresh more.

[Stoopalini]

It's already down to 2v, are you saying I should go down to say 1.8v? I thought anything below 2v causes issues with the GPEC2A ECU .... but maybe that assumption is false...

The misfires are coming well past the 2v threshold is crossed. Is there some other modifier at play which affects this?

Both the PE WOT Thresh and the Torque Management Pedal WOT are set to 2v right now:

PE_WOT_Thresh.JPG

TM_Pedal_WOT.JPG

[Stoopalini]

The WOT Pedal Thresh Offset is set to 5v though. This is the value in the stock tune as well, although I see it is lower in the Hellcat stock tune.

Here's a screenshot of the PE tab from ta stock 2021 Durango Hellcat. Not sure what the offset value is doing though?

2021_Durago_HC_PE_Settings.JPG

[Stoopalini]

Oh, wait ... I see now. It looks like the misfires are triggering leading up to the 2v threshold. I was mistakenly looking at Throttle Volts, not Pedal Volts.

I should also mention I have a Smooth Boost electronic boost controller which is connected to the APPS. So the bypass should be tracking pedal position as well.

[Stoopalini]

Today I was able to log the 1st cold start and drive of the day. I thought the misfires were reduced when my IAT's are low, but it appears it's not the case.

It seems there are times when PE is kicking in even when Pedal V is below the threshold set. It's set at 2v, and this section of the log shows the misfires occurring and then FA Enrichment coming on, and they immediately stop. This is with 1.24 pedal volts.

PE_Below_2v-Pedal.JPG

So what is allowing PE to come on below the Throttle WOT Pedal Thresh and how can I adjust it to happen more often?

Here is the full log:Custom-Throttle_3_cold-start.hpl

Maybe my VE tables need further adjustment to address the misfires?

[smokeshow]

Cat overtemp.

[Stoopalini]

Ahh, thanks! Interesting ... So 34250 (Target Catalyst Temp) is set to 1706, which appears to be the default value. The FA Enrichment starts when cat temp reaches 1708; so this tracks.

Here is what these values look like in my current tune:

Current-Tune_Temp-Control.JPG

Here are the stock values for my vehicle:

2023-OEM-RT_Temp-Control.JPG

And just for comparison, here are the values from a 2021 Durango Hellcat. Looks like 34250 was added sometime afterward, as it's not available in this calibration:

2021-OEM-Hellcat_Temp-Control.JPG


So I assume leveraging the catalytic overtemp controls isn't really a good way to provide enrichment here ... or maybe it is?

Considering 34252, maybe I should lower this? Looking at the log, these misfires are starting even when cat temp is in the upper 1400's though.

[smokeshow]

Power enrichment is a good way to provide power enrichment lol. You've gimped the cat enrichment though, so your mileage may vary on the cats...

[Stoopalini]

Ha! Makes sense. In order to provide power enrichment at the times when it appears to be needed, I would have to lower the WOT pedal volts way down though, like to 1.4v. I imagine this is a sign of something else which isn't setup properly ... like VE maybe?


By "gimped the cat enrichment", do you mean table 34273? Looks like the stock values from my vehicle (as well as the Hellcat stock values) are much higher than my current tune is setup for.

I haven't made any adjustments in these tables myself yet, but what's there is what previous tuners have done. I'm just now trying to learn what was done (and why) to potentially address the remaining issues myself.

I definitely don't want reduced catalytic life ....

[LilSick]

By "gimped the cat enrichment", do you mean table 34273?

34270

[Stoopalini]

34270 in my current tune has the same values as the stock calibrations. In the Hellcat tune, this table is all zeros.

[Dave401Redeye]

Stoopalini. [Quote. It seems there are times when PE is kicking in even when Pedal V is below the threshold set. It's set at 2v, and this section of the log shows the misfires occurring and then FA Enrichment coming on, and they immediately stop. This is with 1.24 pedal volts.]

From what you are describing. It sounds like engine is running lean at part throttle. You are wanting your PE settings to come to work early. Try adding fuel thru your injector fuel mass vs pw table. log injector pw. Look at log for the pw at the time of misfire. Open your pw\fuel mass tables. Table that has pw in the axis and changeable fuel mass column is where to make the change. example pw at misfire is 1.4 mass next to it might be .015 hit your decmil to run .015 out 2 more decmil .015 becomes .01452 i know this sounds backwards. to add fuel you have reduce mass. highlight .01452 box. type .97 if you want to add 3% more fuel at 1.4 pw. .01452 x .97 = .01408 Not done yet. Open your pw vs fuel mass table. You have to change the .01452 to .01408 Click on the left of fuel mass axis column. Popup box will open. click on arrow to open table 2 more decmil rows. (hp has arrows opposite of normal) Copy changes you made on fuel mass vs pw table. Paste the changes to pw vs fuel mass that you have the popup box showing on your screen. I usually make the same % change to the pw box below and the pw box above the 1.4 pw change.

[Stoopalini]

Stoopalini. [Quote. It seems there are times when PE is kicking in even when Pedal V is below the threshold set. It's set at 2v, and this section of the log shows the misfires occurring and then FA Enrichment coming on, and they immediately stop. This is with 1.24 pedal volts.]

From what you are describing. It sounds like engine is running lean at part throttle. You are wanting your PE settings to come to work early. Try adding fuel thru your injector fuel mass vs pw table. log injector pw. Look at log for the pw at the time of misfire. Open your pw\fuel mass tables. Table that has pw in the axis and changeable fuel mass column is where to make the change. example pw at misfire is 1.4 mass next to it might be .015 hit your decmil to run .015 out 2 more decmil .015 becomes .01452 i know this sounds backwards. to add fuel you have reduce mass. highlight .01452 box. type .97 if you want to add 3% more fuel at 1.4 pw. .01452 x .97 = .01408 Not done yet. Open your pw vs fuel mass table. You have to change the .01452 to .01408 Click on the left of fuel mass axis column. Popup box will open. click on arrow to open table 2 more decmil rows. (hp has arrows opposite of normal) Copy changes you made on fuel mass vs pw table. Paste the changes to pw vs fuel mass that you have the popup box showing on your screen. I usually make the same % change to the pw box below and the pw box above the 1.4 pw change.

Thanks, although I seem to have resolved the misfire issue through other means, this is definitely helpful to me in learning more.

It makes sense you reduce the fuel mass per ms to add fuel, assuming I am understanding the table correctly. It's not a demand table but is essentially characterizing how much fuel mass is delivered when the injector is open for a period of time. So if the table states 1.4ms delivers 0.01205g of fuel, and you want more fuel to be delivered with the same time window of 1.4ms ... you need to tell the ECU less fuel is delivered within 1.4ms so it will keep it open longer.

Am I getting that correct?

[B00STJUNKY]

Thanks, although I seem to have resolved the misfire issue through other means, this is definitely helpful to me in learning more.

It makes sense you reduce the fuel mass per ms to add fuel, assuming I am understanding the table correctly. It's not a demand table but is essentially characterizing how much fuel mass is delivered when the injector is open for a period of time. So if the table states 1.4ms delivers 0.01205g of fuel, and you want more fuel to be delivered with the same time window of 1.4ms ... you need to tell the ECU less fuel is delivered within 1.4ms so it will keep it open longer.

Am I getting that correct?

Your understanding is correct.

I would argue, however, that this method is both ineffective if closed loop operation is being utilized (as O2 feedback will continue to bring AFRs back to stoich using STFT and LTFT), and at its core, is a hack method of tuning. I don't mean that in a derogatory way or as an insult to anyone who uses that method. I only offer that perspective inasmuch as there are better ways to tackle the issue at hand, which it sounds like you've already discovered.

I would further add, that as I've followed your other thread where you've discussed this issue at length, I continue to come back to the curiosity of whether these lean spots you've been experiencing are experienced more during steady-state throttle conditions, or if they only seem to crop up during throttle transitions. Admittedly I haven't looked at any of the logs you've provided, but the reason I feel the question has merit is that if the lean issues you've been describing really only do crop up around throttle transitions, then it sounds more like they would be related to airflow model issues.

If your airflow model is not accurately representing what is actually occuring with air charge into the cylinder, then lean and/or rich conditions will be the result, and those conditions will be much more pronounced during throttle and load transitions as the O2 feedback system (particularly STFT) is reactive rather than pro-active in compensating for errors. At that point, commanding a richer AFR target (which it sounds like you've done by changing the goal voltage for the O2 sensors) is simply a band-aid slapped over the airflow model issue that is either being overlooked or ignored.

Will it work to fix the misfire issues? Sounds like it possibly has. But at what expense? At the very least, decreased fuel economy. To what extent, I don't know. It may be insignificant. It all depends on how aggressive you've been in enriching the target AFR mixture. I'm not suggesting it's harmful, but it may not be the most optimal way of correcting the issue you're trying to tackle.

[Stoopalini]

Your understanding is correct.

I would argue, however, that this method is both ineffective if closed loop operation is being utilized (as O2 feedback will continue to bring AFRs back to stoich using STFT and LTFT), and at its core, is a hack method of tuning. I don't mean that in a derogatory way or as an insult to anyone who uses that method. I only offer that perspective inasmuch as there are better ways to tackle the issue at hand, which it sounds like you've already discovered.

I would further add, that as I've followed your other thread where you've discussed this issue at length, I continue to come back to the curiosity of whether these lean spots you've been experiencing are experienced more during steady-state throttle conditions, or if they only seem to crop up during throttle transitions. Admittedly I haven't looked at any of the logs you've provided, but the reason I feel the question has merit is that if the lean issues you've been describing really only do crop up around throttle transitions, then it sounds more like they would be related to airflow model issues.

If your airflow model is not accurately representing what is actually occuring with air charge into the cylinder, then lean and/or rich conditions will be the result, and those conditions will be much more pronounced during throttle and load transitions as the O2 feedback system (particularly STFT) is reactive rather than pro-active in compensating for errors. At that point, commanding a richer AFR target (which it sounds like you've done by changing the goal voltage for the O2 sensors) is simply a band-aid slapped over the airflow model issue that is either being overlooked or ignored.

Will it work to fix the misfire issues? Sounds like it possibly has. But at what expense? At the very least, decreased fuel economy. To what extent, I don't know. It may be insignificant. It all depends on how aggressive you've been in enriching the target AFR mixture. I'm not suggesting it's harmful, but it may not be the most optimal way of correcting the issue you're trying to tackle.

Thanks man, I truly appreciate your thoughts here, and you're spot on. Your comments reflect a lot of what the two pro tuners I engaged were saying. They both chased the MAP characterization at first, thinking there was something off with the data there. One of them eventually did what was suggested above, but the other said he thinks there is something additional affecting the air flow model which isn't being exposed in the VCM Editor UI.

The misfires and lean spikes I was experiencing were only happening during throttle transition. Steady state light throttle would cause some KR, but not misfires. Then when increasing throttle input, the KR would stop and a few misfires would trigger. So maybe it was going rich during steady state causing the KR and then going lean with transition, causing misfires?

You're also correct in that I seem to have been able to compensate for whatever is happening in the airflow through manipulation of the Control Goal and PRatio boundaries (big thanks to Spray-Cam for showing me this, I learned a lot through that exercise).

I haven't really dug into the airflow model side of things yet, so I'm largely still ignorant in that area. I feel I'm starting to gain some knowledge around the fueling side of things, but probably need to dig into the airflow side now to continue my learning journey.

Curious ... in your opinion ... do you think a rolled or damaged o-ring between the heads and the supercharger's intake could be the root cause of airflow model issues? I initially suspected maybe this was the case, but Whipple and the previous tuners have all 3 said they don't think so. I did smoke test the supercharger and didn't see any leaks. I suppose if an o-ring was leaking I'd probably see it in the data for that individual cylinder though, right?

Cylinders 7 and 8 are the ones which end up being problematic for misfires. Here is a look at the misfire counts from a previous log. This was before I decided to dig in and try to learn enough to become comfortable making my own adjustments:

Misfire_Counts_MOD13.JPG

This was a 4 1/2 minute drive to test a tune revision tuner #2 provided me. Some revisions were better and some worse than this ... but it was always cylinders 7 and 8 which exhibited the misfire issue. Cylinders 1 - 6 only ever generated 1's and 2's from time to time. I wondered if maybe this could be a sign of a heat problem, especially with IATs typically so high ... although in the particular log I took that screenshot from the IAT's were only in the 120's as it was one of the 1st drives of the day so it wasn't heat soaked yet.

I definitely do want to eventually arrive at the optimal configuration for fixing things. Longevity is the top priority here, which is why I'm so focused on the misfires and KR. But MPG has been a complaint from the wife as well. It was in the 11-12 range for a while. It's now averaging 13 after the changes I've made to it, but I imagine it's still not where it can be if the issues get resolved properly.

Prior to the Whipple, we were getting around 17 MPG.

[LilSick]

dont use smoke for that... use starting fluid

2 questions for you (plz wait til after he answers boostjunkie)

1) when yer 02v is high (near 1 volt) do you think the sensor is seeing fat or lean?

2) when your fuel trim is at -15 do you think your pcm is pulling fuel or adding it?

i wanna see if we are on the same page before i dive in : )

[Stoopalini]

dont use smoke for that... use starting fluid

2 questions for you (plz wait til after he answers boostjunkie)

1) when yer 02v is high (near 1 volt) do you think the sensor is seeing fat or lean?

2) when your fuel trim is at -15 do you think your pcm is pulling fuel or adding it?

i wanna see if we are on the same page before i dive in : )

Hmm ... so it's my understanding the trims reflect the action the ECU is taking. So -15 fuel trim would mean it's detecting a rich condition and pulling fuel.

In terms of the voltage reading ... since it's measuring oxygen content, I'd have to say being near 1v would mean there is less O2 in the stream and therefore rich??

[LilSick]

no bro

i build/blueprint engines

i cut lights/drive

and i tune

i am not a english major or a computer engineer

gonna let boostjunkie explain why its no

he is good like that

jelly : )

[B00STJUNKY]

no bro

i build/blueprint engines

i cut lights/drive

and i tune

i am not a english major or a computer engineer

gonna let boostjunkie explain why its no

he is good like that

jelly : )

I appreciate the high praises, but honestly, I'm just a tuning and turbo enthusiast that occasionally tunes for other folks. It's definitely not my bread and butter. I'm actually an Industrial Millwright by trade.

Regarding your response in the negative to the answers Stoopalini gave to your questions, I may well be missing context, or have misunderstood the questions.

It is my understanding that narrowband sensors will read near to 1.0 volts during rich conditions, and near 0 volts during lean conditions.

It has also been my understanding and experience that negative fuel trims indicate that the PCM is removing fuel, and positive fuel trims indicate that the PCM is adding fuel.

Have you observed the opposite?

Keep in mind, as I've mentioned before, the majority of my tuning experience is with NGC controllers. But from the little I have experienced with GPEC controllers, anecdotally, I recall it behaving the same way.

I'm certainly open to being corrected.