Deceleration pop

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I’m starting to get some tuning time and have a issue during decel with exhaust pop. I don’t use over-run fuel cut, mostly because I don’t comprehend its settings yet. I’ve tried it and had undesirable results.

Is anyone using the fuel/timing table to tune the areas of pop, or should I just get a PhD in over-run and figure it out?
 
I can share my overrun settings if you'd like. Main thing is don't expect miracles from it. The transition back to run can be a little surgy but I hardly ever notice it anymore. It beats a backfire.


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FMOS Racing said:
I can share my overrun settings if you'd like. Main thing is don't expect miracles from it. The transition back to run can be a little surgy but I hardly ever notice it anymore. It beats a backfire.


Sent from my motorola edge plus 5G UW (2022) using Tapatalk
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That may be helpful, I get into trouble with it in Engine State - Overrun MAP threshold I think, using 20.0 kPa.

Using the settings in the attached image.
 

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Raymond_B said:
Have you been able to datalog it? Would be good to see that 1st.
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Here is a run to the store, I happens as I lift and decelerate from around 55 mph or so. I'm not sure my marks made it into the file.
 

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I had a couple ideas but couldn't find any proof to them in the datalog. I also didn't see the marks so I was just looking at tps and RPM to see when you where decelling. My settings compared to your screen shot aren't a whole lot different. only change that may make a differences is my delay is .8 instead of 1.1. Which depending which cell on the VE you get into during that 1.1 seconds it may be excessively rich or lean for a split second. check the bottom rows of your VE. With yours being an auto I'm not sure how much drag your get compared to mine on decel.
 
FlatOut said:
I had a couple ideas but couldn't find any proof to them in the datalog. I also didn't see the marks so I was just looking at tps and RPM to see when you where decelling. My settings compared to your screen shot aren't a whole lot different. only change that may make a differences is my delay is .8 instead of 1.1. Which depending which cell on the VE you get into during that 1.1 seconds it may be excessively rich or lean for a split second. check the bottom rows of your VE. With yours being an auto I'm not sure how much drag your get compared to mine on decel.
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Thanks for looking, appreciate it. I took another shot with a mark - and since you mentioned the automatic I have to say this only happens in OD. I usually click the OD button off and drop into 3rd which avoids the popping. I have a fairly high stall at 3400 so essentially I'm coasting clutch in in 3rd. My converter is in Lockup in OD at 1500rpm 50+ MPH.

I think I'll do a short trip and log the difference between OD and 3rd deceleration and see - I does look rich at the moments after the throttle closes.




decel.png
 
I set my bottom VE row really low. It only ends up there during decel.

I keep forgetting to get on the computer in the evenings, but I'm off tomorrow and will try to take a look myself then, and share my settings.
 
These are the white truck's settings. The red truck's are identical except for a bit larger Slow Accel and Decel thresholds due to a slight more rowdy overall engine/trans behavior.
1711652689192.png
 
Seems that I did need to lean out VE in that narrow lower MAP/RPM, my table kinda looks like it’s developing again. I also changed my converter lockup in OD to my normal highway speed of 70mph.

So far overrun seems okay.
 
I lock up in every gear but 1st at 35 mph, but I'm also trying to get some kind of acceptable mileage out of mine. Though I do use the same strategy in both trucks because my old experimenting with the TC and quarter mile passes liked it that way.
 
FMOS Racing said:
I lock up in every gear but 1st at 35 mph, but I'm also trying to get some kind of acceptable mileage out of mine. Though I do use the same strategy in both trucks because my old experimenting with the TC and quarter mile passes liked it that way.
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Do you know if lockup in all 3 gears was the factory strategy?
 
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