2019 5.3 with Flowmaster Delta flow 40 series

[DHBWA]

I initially covered all 6 resonators with factory muffler and it was almost what I wanted. I preferred to buy the AFE Apollo muffler upgrade but it’s on back order. After a bunch of research and having an old version series 40 on my 1994 5.7 I ordered the SS version delta flow 40 series and had it installed and removed the flapper which I had wired open.

With all 6 resonators covered it was a little loud with a little drone. Started uncovering resonators and now have 1.5 on each side covered. 
Now to why I posted this topic.

Anyone else with this or another performance muffler notice a little blubbering/ rumbling on decel when below 1200 rpm?? If you hold the downshift and decel say at 2500-3000 it’s smooth until you down to a real low rpm then you can hear it burbling….. Seems strange to me.

 I don’t really like it…

 I also have a Range Pulsar.

Thoughts??

Edited January 27, 2023 by DHBWA

[Russ757]

yep.. with or without the Pulsar. I have to go through the burbs so lots of coasting at which you get the putt putt putt. Not sure if thats what youre referring to. This with a flowfx catback system

[DHBWA]

Yup. I called Flowmaster (Holley) and he said it’s because of the engine design in combination with a chambered muffler. I can’t win. Every time I change exhaust on a vehicle I end up redoing it. 
he suggested and I just ordered a Hooker VR304 3”-3” muffler (oval glass pack) you don’t hear much about them but what he said made sense…

I have tried covering all, some and none of the 6 screen resonators with no gain yet…..

[diamondd2]

Why don't you try uncovering the screens and putting the flapper back on.

[DHBWA]

I really don’t want to go to the effort on the flapper but will try once more with screens all uncovered and once with all covered 

[DHBWA]

3 hours ago, Russ757 said:

yep.. with or without the Pulsar. I have to go through the burbs so lots of coasting at which you get the putt putt putt. Not sure if thats what youre referring to. This with a flowfx catback system

I just figured out that your FlowFX muffler isn’t a chambered muffler. It’s Flowmasters version of a Magnaflow (oval glass pack) so my idea of going to a Hooker VR304 probably won’t help…..

[DHBWA]

With all resonators uncovered it quieted it down overall and subdued the put-put that it’s mostly a non-issue.

 I doubt I will install the Hooker. 
 

I tried it again this morning with all 6 resonators covered and didn’t notice any drone and really like the sound. The put-put was louder but that is almost better if it’s going to do it.

More to come…

[DHBWA]

Uncovered the resonators for the commute. Cruising there is zero drone and sounds almost stock. Idle and acceleration is throaty but subdued to an adult level. I will probably cover all resonators for tomorrow’s commute and see…..

[DHBWA]

Covered them all for the return trip. Too loud for me and the put-put-put at slow decel was pronounced. Probably stick with having them all uncovered. Wish it was just a tad louder but I have a history of fixing things until they are broke…..I better quit while I am 90% satisfied……

[CamGTP]

I don't have any data logs on this computer or really any that I've done recently to show but these computers will enable decel fuel cut off while coasting to a stop. They will also re-tard the ignition timing to negative values while coasting and when it needs to make down shifts. The sharp drop in timing is to pull torque/power and make it easier for the transmission to shift gears.

 

Decel fuel cut off turns off the fuel injectors completely and it's using the engine as an air pump to slow the vehicle down. This is likely what is happening and the answer to why you hear what you hear.

[DHBWA]

Thanks Cam.

Makes sense and supports my thoughts that it probably won’t matter what muffler I have except to say the quieter the muffler the less I will hear it.

[DHBWA]

Another tidbit. 
Removed the Range Pulsar to have some work done at the dealership and with it removed 90% of the low speed - low rpm decel put-put noise. Obviously something to do with the DFM. Of course it makes other awful noises…..

Have an appt next Thursday to do some muffler tests but not convinced I’ll get what I want….

Edited February 1, 2023 by DHBWA

[DHBWA]

Installed a Hooker straight thru packed muffler.

To me it’s a Magnaflow copy.

It’s quieter and thusly the decel putt putt is less noticeable. Although quieter overall it seems to drone more at 70.

I really really prefer the crisper higher pitch of the Flowmaster. 
Just need to decide if I can ignore the decel puttering with the FM.

 

Hope this helps someone someday…