O2 switching and fuel open/closed loop questions

I'm a gen5 4cyl guy, not getting very far with a problem. So I'm trying here for what I think may be a gen 5 problem for multiple platforms. I have gotten a lot of valuable tuning info from gen4/gen5 threads for my 4cyl so I thought why not.

I am having a fueling issue when going to wot before PE mode kicks in. Basically I go to WOT and fueling dips really quick to an unknown 13.45 afr. for a split sec. Then back to stoich for about a half a sec. Then back to the unknown 13.45 afr. for about a sec. Then back to stoich for about a sec...... then PE mode finally kicks in (~12.25 afr). That last jump from the unknown 13.49 afr to stoich is where a large power hit comes from as you can see by the afr and torque traces on the pic below.

I have gone through all PE tables and this isn't related to those. It has to be a parameter under the o2 sensor switching tables or open loop/closed loop fueling tables. I just cannot figure out which and where? Any ideas, thoughts, or input is greatly appreciated.

I read about gen4 and gen5 v8 slow o2 switching causing a similar issue, but cannot find that thread again. It got me thinking this could be related to my problem? Just not sure where to start with GM slow 02 switching? And I am watching my Fuel System Status pid which also shows it going back and forth between close and open loop fueling. So I'm also thinking it could be related to something with OL/CL control or multipliers?

I am slightly new to GM tuning, coming from Chrysler tuning which isn't even comparable to this. So I apologize if this is an obvious GM thing to some. I haven't had much luck diagnosing/investigating the problem.

Attachment 140352

Attachment 140351

Post your current tune and we can assist you with the PE issue.

If you lower dynamic airflow RPM's below the point of making the hit(stabbing the throttle), it can cause a lean spike as the ECU ignores a lot of the VVE data and listens to the MAF. The MAF has a slight delay in reported airflow. VVE is immediate as it relies on a ratio derived from the MAP sensor.

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Originally Posted by kevin87turbot

Post your current tune and we can assist you with the PE issue.

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Originally Posted by TriPinTaZ

If you lower dynamic airflow RPM's below the point of making the hit(stabbing the throttle), it can cause a lean spike as the ECU ignores a lot of the VVE data and listens to the MAF. The MAF has a slight delay in reported airflow. VVE is immediate as it relies on a ratio derived from the MAP sensor.

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This is my current tune and current 3rd gear low rpm WOT pull log.

Attachment 140426
Attachment 140427

I did try adjusting "[ECM] 12440 - Open Loop Airflow Gain vs. MAP vs. RPM: This table is used to multiply the Equivalence Ratio when in open loop mode." As I felt it was best fit for what I am trying to accomplish, basically force 13.45 afr in open loop fuel mode to get rid of that fueling dip in power before PE kicks in. But it appears the table isn't active/used as no change happened unfortunately.

I am looking at the dynamic airflow rpms and it's set very high, outside of my max rev range? If I understand you correctly, this setting doesn't apply to my problem then?

But now you got me thinking. I read somewhere I could force VVE/speed density mode and not utilize MAF? Curious if this issue happens when forced in speed density to see if it is actually related to the MAF sensor?

I appreciate the help.

Did this start after tuning or has it always done it? I only ask because some things were adjusted incorrectly.

Peak torque - put back
Max torque per gear - max out
Overboost limit - you can max
PE enable pedal and enable torque - use both - lower pedal to something in the 30's, raise torque off of 0 to something like 15 or 20 %

Adjust things from there.

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Originally Posted by GHuggins

Did this start after tuning or has it always done it? I only ask because some things were adjusted incorrectly.

Peak torque - put back
Max torque per gear - max out
Overboost limit - you can max
PE enable pedal and enable torque - use both - lower pedal to something in the 30's, raise torque off of 0 to something like 15 or 20 %

Adjust things from there.

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It's always been there IMO. As I adjusted the Virtual Torque Tables more and more, the worse it got. At first I thought it was the exhaust VVT swinging @ WOT (another issue) that was causing the problem. But the more and more I looked at it, I feel it's fuel related. Keeps switching ol/cl fueling after going 100% throttle.

I'm thinking it's related to either the MAF to Speed Density transfer, and/or either the MAF or VVE tables needing to be calibrated/tuned. I so far cannot figure out anything in the fueling related tables.

Honestly I am hesitant to try too much more as I don't have the wideband/downpipe just yet installed. I feel like I've gone far enough without actual fuel readings to verify with. Don't want to chance it I guess anymore than I already have.

The max torque per gear limit was set that way as a cheesy cutoff to not get too wild in the first gear. And other gears to limit boost to about 21psi peak without knowing the actual AFR.

Out of curiosity, why put Peak torque back?

I appreciate your feedback. Thank you.

Peak torque is the setting the PE torque to enable PE table is looking at to enable and keep in PE. It's not a limiter. You should also know that anything that limits torque - (peak torque per gear) - will usually cut fuel to limit torque on gen V's. Jason and I are both looking into some TCS settings right now because we're tired of fuel cuts happening on LT4's to control traction ;) You need to set yours up to go into PE with boost. Yours isn't and wasn't from the factory. That's why I suggested the changes that I did.

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Originally Posted by GHuggins

Peak torque is the setting the PE torque to enable PE table is looking at to enable and keep in PE. It's not a limiter. You should also know that anything that limits torque - (peak torque per gear) - will usually cut fuel to limit torque on gen V's. Jason and I are both looking into some TCS settings right now because we're tired of fuel cuts happening on LT4's to control traction ;) You need to set yours up to go into PE with boost. Yours isn't and wasn't from the factory. That's why I suggested the changes that I did.

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Excellent information. Greatly appreciate it as well. I will change those around now that I know more info about that parameter.

You can see in the log you posted above it's limiting torque. Cut fuel and throttle then ramped both back in about half way through the pull.

Will it allow you to add in air calc mode into the channels? If it will, grab another wot pull like the one above please. Doesn't have anything to do with this. Just needed for another one so if you don't want to it's ok ;)

Are you sure that traction control is not kicking in .. I think it will be either a traction control settings or max torque settings are off.. assuming VVT is valid

from the log the maximum engine torque value reached was around 311 lb-ft while in the tune file peak torque table maximum value is 274 lb-ft

try this:
- max RPM vs Gear table
- raise Peak Torque table 15% from 1800 to the last column
- raise Overboost limit 12% from 1800 to the last column

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Originally Posted by GHuggins

You can see in the log you posted above it's limiting torque. Cut fuel and throttle then ramped both back in about half way through the pull.

Will it allow you to add in air calc mode into the channels? If it will, grab another wot pull like the one above please. Doesn't have anything to do with this. Just needed for another one so if you don't want to it's ok ;)

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I purposely had the torque per gear set to limit my boost to about 21 psi because I don't know my actual AFR and am only going off my narrowband sensor. Like a safety net until my wideband is installed. I only did this because we have a similar setting at work on our diesels and its effective with those at limiting power. I watch the throttle % to see the limitation and was under the impression that it mainly used that to limit power from the torque per gear and the virtual torque tables. But I see what you are saying and the OL/CL switching could possibly be related to that. I don't know about the air calc mode into the channels? I don't quite understand what you are referring to?

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Originally Posted by GHuggins

Peak torque is the setting the PE torque to enable PE table is looking at to enable and keep in PE. It's not a limiter. You should also know that anything that limits torque - (peak torque per gear) - will usually cut fuel to limit torque on gen V's. Jason and I are both looking into some TCS settings right now because we're tired of fuel cuts happening on LT4's to control traction ;) You need to set yours up to go into PE with boost. Yours isn't and wasn't from the factory. That's why I suggested the changes that I did.

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I'm not too sure about this. I made all the changes you stated except setting my torque per gear to 325 ft lbs. My calculated engine torque maxed out at about 200 ft lbs on my last log/drive I just did? And you could feel the power loss difference obviously. Which is confusing because I was making calculated 310, with peak torque set to about 280? PE fueling was still delayed, but I haven't looked if it's still going in and out of OL fueling.

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Originally Posted by rousha

Are you sure that traction control is not kicking in .. I think it will be either a traction control settings or max torque settings are off.. assuming VVT is valid

from the log the maximum engine torque value reached was around 311 lb-ft while in the tune file peak torque table maximum value is 274 lb-ft

try this:
- max RPM vs Gear table
- raise Peak Torque table 15% from 1800 to the last column
- raise Overboost limit 12% from 1800 to the last column

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I set the TCS max torque higher than my max torque per gear. 99% sure it's not TCS related. It's max torque per gear that's limiting me and I am aware as I have it set to limit to 310 purposely. My main issue was to try and understand why I'm going in and out of OL fueling. Not the torque limiting. But now I think it's possible they could be related.

Don't know if it's possible - it should be - but you need to limit power via boost controls instead of torque. These always cut fuel as it has the biggest impact and throttle to limit torque.

Get your wideband installed and go from there. You can raise the lower end of peak torque. You want peak torque somewhere right over actual but don't go overboard with it. I have yet to see peak torque cut throttle like people claim it does. It's almost always DD or something else in general when throttle gets cut.

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Originally Posted by GHuggins

Don't know if it's possible - it should be - but you need to limit power via boost controls instead of torque. These always cut fuel as it has the biggest impact and throttle to limit torque.

Get your wideband installed and go from there. You can raise the lower end of peak torque. You want peak torque somewhere right over actual but don't go overboard with it. I have yet to see peak torque cut throttle like people claim it does. It's almost always DD or something else in general when throttle gets cut.

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Exactly, if you use torque limits to control boost this will create more complicated and hidden issues which are difficult to address.. gen 5 torque tables actually interconnected to too many other tables and it is very hard to fully understand how it really works.

I remember one L83 truck with CAI and cat-back only facing knock (up to 8 degrees) under acceleration (true audible knock) which should not be from timing (it was conservative) or fueling, VVT, VVE and MAF all are valid. Finally raised Peak torque table a bit more and the knock reduced to around 3 degrees, raised more again and no more knock. It was a surprise for me cause throttle was fully open.

So from my experience with Gen 5 trucks (not sure about other applications):
Torque limits can cut fuel and/or close throttle and/or create knock retard

So far the only limiting factors I've seen with this power train/e80a ECM is either the torque per gear/rpm and the virtual torque tables. I will agree with you both this isn't an optimal way to do this. I will probably reconfigure the virtual torque tables down a bit.

With the little adjustments I've done to DD, it all seemed mostly related to throttle input. Meaning if I up the DD torque, throttle is more touchy.

I really appreciate the input. Coming from Chrysler tuning, it's all ETC based instead of torque. So it's a whole new learning curve.

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Originally Posted by rousha

Exactly, if you use torque limits to control boost this will create more complicated and hidden issues which are difficult to address.. gen 5 torque tables actually interconnected to too many other tables and it is very hard to fully understand how it really works.

I remember one L83 truck with CAI and cat-back only facing knock (up to 8 degrees) under acceleration (true audible knock) which should not be from timing (it was conservative) or fueling, VVT, VVE and MAF all are valid. Finally raised Peak torque table a bit more and the knock reduced to around 3 degrees, raised more again and no more knock. It was a surprise for me cause throttle was fully open.

So from my experience with Gen 5 trucks (not sure about other applications):
Torque limits can cut fuel and/or close throttle and/or create knock retard

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This is correct. I actually get into some of these background controllers which is why I possibly understand what you're saying more than most. I've even seen throttle and DD cause torque management and timing pulls on easy take offs like what you're describing. There are a couple of background tables in particular that will play into this a lot. They often cause misfires when taking off in first gear with high stall converters. Everybody chases the misfires when they aren't the problem.

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Originally Posted by GHuggins

This is correct. I actually get into some of these background controllers which is why I possibly understand what you're saying more than most. I've even seen throttle and DD cause torque management and timing pulls on easy take offs like what you're describing. There are a couple of background tables in particular that will play into this a lot. They often cause misfires when taking off in first gear with high stall converters. Everybody chases the misfires when they aren't the problem.

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Thats why for me I will never touch DD unless it is necessary. It drived me crazy until returned 100% stock and focused on VT and Peak table then all issues resolved

I actually tune the DD tables on top of all the other tables. Find things work out better. It's not hard to do either. Just log etc position vs pedal and apply that correction factor. If you tune in the throttle area or pedal progression tables this will be 100% necessary.

To the OP, I wouldn't change the VT tables to try and limit torque. Dial in delivered from 1200 up, but that's as far as I would go. I would focus on killing the limiters and get it to add fuel.

I have changed literally every open loop EQ multiplier table and none of them actually changed the fueling where the power dip is during the first couple sec going to wot. I don't know what else to do. If just the one airmass per rpm multiplier worked, it'd be fixed.

My only thought now is about the VT table. I have been adjusting the Airmass tables only. Am I an idiot and should have also been adjusting the MAP table too? As supposedly it runs both and switches back and forth between the two?

As for torque limiting. I have adjusted the Airmass VT tables down to limit power to about 320 ft lbs calculated flywheel torque. And took all other limiters off. So it essentially matches the OE setup, except with more power.

Post the latest tune and log please.

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Originally Posted by GHuggins

Post the latest tune and log please.

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Sorry. Between the weather and not feeling too great lately, I hadn't done too much. I went out for about 2 hours this morning logging and making subtle changes here and there. I believe I found a fix to the power dip culprit. During the first few sec going to wot at the point I have been, it appears to be slightly dipping into a different VVT Virtual Torque table. Just enough to create a dip. I still believe the cl/ol fuel switching back and forth is the actual issue, but altering the points where it dips into the intake cam VVT map for a split second has made a drastic change enough that it's almost gone.