Popping in the exhaust

[Yves]

I'm going to keep this apart from my tuning strategy thread to deal with this specific problem.

I get a lot of popping in the exhaust during decel. I include a log of my last run. I used autotune to see where it would change and pushed the apply/save buttons several times during driving. EGO was on

I could also glance at the screen a couple of times during decel and it seems to pop especially in those low kPa zones (30-40) where I have AFR ratios of 14 and up.

Please also take a look at the AE and decel in this run. I currently have the following settings for AE :
- Tpsdotthreshold : 150
- decel fuel amount : 90
- PW at %/s 9.3 : 5.2
- PW at %/s 38 : 8
- PW at %/s 139.4 : 14.6
- PW at %/s 199.4 : 17.6

I tried settings of decel of 95 but it seemed to be popping more.

I'm unsure if the popping is cause by a too lean AFR in those regions, too much fuel during decel.

Do I need to implement a fuel cut and if so, what settings do I use.

Please review. Thanks

PS: log file editted to get saved in here.

[elutionsdesign]

I personally would try tuning it out before using the fuel cut settings, I've seen people chasing their tails due to fuel cut being active.

Yes, try much leaner on decel, drop it to 50% and see what it does. Don't let big lean numbers bother you when tuning this, its under no load whatsoever and needs just enough fuel to smoothly transition back to running outside of the decel area. Putting big timing numbers in the timing table in this are help as well. Like if your max timing is 36 try 40-50 in the area it pops on decel. Again, there is no load. Many factory ECU's cut fuel completely and the wide band output goes offscale high. I had one that read LEAN when it went above 22 AFR so rolling through the mountains coasting down the hills I'd see LEAN for minutes at a time.

[Yves]

I did a short testdrive with the AFR tables in those lower regions all reset to an AFR of 13.8. I set the decel fuel amount in AE to 100%.

The annoying popping seems to be gone. But I do have some backfire into the intake now...

[Yves]

Correction : the popping was there but less. It's usually when coming off higher rpm.

I tried map/TPS AE in various % and it seemed to help some. Decel fuel at 80 seemed to help also.

I don't know about others but I'm not comfortable with backfiring and popping. I fear that it might cause damage (and not just the exhaust)

[elutionsdesign]

You have neither AE or DE activating in that last log, drop the threshold so it can work.

If you're afraid of some popping get someone else to tune it.

[Yves]

Yes, yesterday after trying to figure it out, I finally found what to look for and indeed it wasn't cutting in. I set it as low as it could go during idling and I have it set at 20 vs 180 before. The car runs better now, decel fuel cut seems to cut in as well. The decel fuel cut is currently set at 80, so I might even try 70.