davekro
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In my research on the causes and remedies for drone, I read that increasing exhaust system (pipe, muffler or tips) diameter at the end of the system gives the desired lower tone, but is also notorious for creating drone. Maybe that is why axle backs with 2 ½” and 3” pipes along with their larger diameter (and smaller size) straight thru mufflers can also be prone to drone?
For my situation, now knowing my Magnaflow mufflers inlets/outlets were in fact 2½” AND my installer also added a piece of 2½” extension in front of my muffler, I DID NOT have the same installation as the other three cars w/ MF 11365’s! I was way past 30 days and the mufflers also had hanger rod welded to them, so I needed to figure a way to mod these…
I was the only person of four now with Magnaflow mufflers to get drone. I finally confirmed that I was shipped 2½” inlet/outlet mufflers (11366) not 2¼” (11365). Blaster is the first convertible to install MF 11365 mufflers and he got no drone either. To try to reduce my drone I cut my mufflers and tips (my first tips were MF 35136) off to copy Blaster’s convertible muffler installation. Thanks to Russian, and AJfrench for supplying me with details of their Magnaflow 11365 installations. And Huge thanks to Blaster for the details he supplied on his CONVERTIBLE’s 11365 installation!
His installer put smaller pipe inserts between his 2¼” tailpipe and 2¼” muffler inlet and also between the 2¼” muffler outlet and the tips. (So he actually has short pieces of smaller dia. pipe at his muffler inlet & outlet than OEM!) To copy that concept as best I could here is what I did...
Phase 1 muffler outlet:
To the outlet of the mufflers I inserted a 2¼” dia. x 10” long pipe. I attached it with 3 screws that I tapped thru the muffler’s 2½” outlet pipe.
My 1st test was just this 10” long 2¼” inserted pipes at the back of the muffler. The pipes were 2½” out from the top of the rear painted cut out. This sounded to me and my wife like the resonance was still there, but not annoying at all. And my readings with the decibel meter didn’t really change, it remained about 96 Db. But it was less annoying and very acceptable. The loudness inside the cab from the exhaust tone sounded less loud than before, but still very good. When I put the top down I still found the exhaust over the full range to be a bit less loud than before but it still sounded good (throaty and loud enough
). Overall very positive change!
(All interior cab sound tests were with the convertible top up and the windows up.)
My 2nd test, I slid ‘bolt on’ (temporary) 9” resonated tips over the 10” pipe so that the 2 ¼” tailpipe was 2 ½” in from the bottom of the angled resonator tip. Top of the res. tips were 4” out from the top of the rear painted cut out. This looked weird, but I wanted to be sure to eliminate the drone ;), and then shorten for an appropriate look.
My 3rd test was sliding the tips closer in so that the 2¼” tail pipe lined up with the bottom edge of the angled resonated tip. Top of the res. tips were 3¼” out from the top of the rear painted cut out.
Phase 1 test drive results: Adding the 10” piece of 2¼” pipe after the muffler was the main remedy to reducing the drone. Sliding the resonator tips over this pipe with even extending the distance out from the back of the car from 2½” to 4” seemed only to make a nuanced change to an overall softer exhaust tone (and maybe slightly softer drone?) from just the 2 ¼” tail pipe.
Phase 2, muffler inlet:
To see if I could reduce the drone a little bit more, I installed the smaller diameter 2¼” inserts also in front of the muffler between my tailpipe and the muffler inlets (4¼” long pipes to reduce the pipe i.d. here too). I then slid the muffler over the previously welded on tailpipe extension (pics below). I also added a hanger bracket above this connection for extra support because it’s not welded.
Phase 2 test drive results: With the smaller pipe in front now too, it did seem to make the drone even a bit less as well as the over all tone a bit less too. So, the whole sound range is now quieted somewhat, but the drone is no longer annoying at all. The low tone I now hear at the 1400 to 1900 rpm range inside the car no longer hurts my ears, and is very acceptable.
Bottom line… I feel that my drone issue is solved. Now I will look for a 9” angle cut double wall, NON-resonated tip. If anyone has suggestions for 2 ¼” – 2 ½” clamp on double wall angle cut non-res tips, I’m all ears! (Preferably in a 3 ½” to 4” o.d. J)
I just learned, duh, that the ‘resonated’ tip does not muffle or quiet the sound it changes it (usually louder). In my case the change amplified my drone. So with the 2¼”” tailpipe inserted thru my experimental resonated tips it sounds much better. I expect that with the same type of tip, but without the perforations of the resonated tip, it may be even a little better sounding. We shall see.
Soon I’ll post a video similar to the one I did after my initial Magnaflow muffler and tips installation to have a back to back comparison.
PS. Sorry for the loooong post, but for as much time as I have invested in this, I figured I could at least share the full process of what I did and learned. Hopefully it might save someone else from these drone issues.
..................................................
Phase 1 muffler outlet:
(if anyone can tell me how to insert text between pictures, that would be great. Mine just always appear after the last text entered. :doh
Phase 2 Muffler Inlet:
For my situation, now knowing my Magnaflow mufflers inlets/outlets were in fact 2½” AND my installer also added a piece of 2½” extension in front of my muffler, I DID NOT have the same installation as the other three cars w/ MF 11365’s! I was way past 30 days and the mufflers also had hanger rod welded to them, so I needed to figure a way to mod these…
I was the only person of four now with Magnaflow mufflers to get drone. I finally confirmed that I was shipped 2½” inlet/outlet mufflers (11366) not 2¼” (11365). Blaster is the first convertible to install MF 11365 mufflers and he got no drone either. To try to reduce my drone I cut my mufflers and tips (my first tips were MF 35136) off to copy Blaster’s convertible muffler installation. Thanks to Russian, and AJfrench for supplying me with details of their Magnaflow 11365 installations. And Huge thanks to Blaster for the details he supplied on his CONVERTIBLE’s 11365 installation!
His installer put smaller pipe inserts between his 2¼” tailpipe and 2¼” muffler inlet and also between the 2¼” muffler outlet and the tips. (So he actually has short pieces of smaller dia. pipe at his muffler inlet & outlet than OEM!) To copy that concept as best I could here is what I did...
Phase 1 muffler outlet:
To the outlet of the mufflers I inserted a 2¼” dia. x 10” long pipe. I attached it with 3 screws that I tapped thru the muffler’s 2½” outlet pipe.
My 1st test was just this 10” long 2¼” inserted pipes at the back of the muffler. The pipes were 2½” out from the top of the rear painted cut out. This sounded to me and my wife like the resonance was still there, but not annoying at all. And my readings with the decibel meter didn’t really change, it remained about 96 Db. But it was less annoying and very acceptable. The loudness inside the cab from the exhaust tone sounded less loud than before, but still very good. When I put the top down I still found the exhaust over the full range to be a bit less loud than before but it still sounded good (throaty and loud enough
). Overall very positive change!(All interior cab sound tests were with the convertible top up and the windows up.)
My 2nd test, I slid ‘bolt on’ (temporary) 9” resonated tips over the 10” pipe so that the 2 ¼” tailpipe was 2 ½” in from the bottom of the angled resonator tip. Top of the res. tips were 4” out from the top of the rear painted cut out. This looked weird, but I wanted to be sure to eliminate the drone ;), and then shorten for an appropriate look.
My 3rd test was sliding the tips closer in so that the 2¼” tail pipe lined up with the bottom edge of the angled resonated tip. Top of the res. tips were 3¼” out from the top of the rear painted cut out.
Phase 1 test drive results: Adding the 10” piece of 2¼” pipe after the muffler was the main remedy to reducing the drone. Sliding the resonator tips over this pipe with even extending the distance out from the back of the car from 2½” to 4” seemed only to make a nuanced change to an overall softer exhaust tone (and maybe slightly softer drone?) from just the 2 ¼” tail pipe.
Phase 2, muffler inlet:
To see if I could reduce the drone a little bit more, I installed the smaller diameter 2¼” inserts also in front of the muffler between my tailpipe and the muffler inlets (4¼” long pipes to reduce the pipe i.d. here too). I then slid the muffler over the previously welded on tailpipe extension (pics below). I also added a hanger bracket above this connection for extra support because it’s not welded.
Phase 2 test drive results: With the smaller pipe in front now too, it did seem to make the drone even a bit less as well as the over all tone a bit less too. So, the whole sound range is now quieted somewhat, but the drone is no longer annoying at all. The low tone I now hear at the 1400 to 1900 rpm range inside the car no longer hurts my ears, and is very acceptable.
Bottom line… I feel that my drone issue is solved. Now I will look for a 9” angle cut double wall, NON-resonated tip. If anyone has suggestions for 2 ¼” – 2 ½” clamp on double wall angle cut non-res tips, I’m all ears! (Preferably in a 3 ½” to 4” o.d. J)
I just learned, duh, that the ‘resonated’ tip does not muffle or quiet the sound it changes it (usually louder). In my case the change amplified my drone. So with the 2¼”” tailpipe inserted thru my experimental resonated tips it sounds much better. I expect that with the same type of tip, but without the perforations of the resonated tip, it may be even a little better sounding. We shall see.
Soon I’ll post a video similar to the one I did after my initial Magnaflow muffler and tips installation to have a back to back comparison.
PS. Sorry for the loooong post, but for as much time as I have invested in this, I figured I could at least share the full process of what I did and learned. Hopefully it might save someone else from these drone issues.
..................................................
Phase 1 muffler outlet:
(if anyone can tell me how to insert text between pictures, that would be great. Mine just always appear after the last text entered. :doh
Phase 2 Muffler Inlet:
Sponsored
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