vibration, harmonic?

[remusrm]

I remember before there was an issue with harmonic vibration from the exhaust, I feel my car experiences this while in an incline and light pedal tap. Does anyone experience this?

[Fummins]

I've had a lot of 2017's that had a resonance vibration under light throttle, mostly at low speeds. We have a couple 2019's that started doing this with relatively low mileage, around 60k miles ish. Maybe less.

This guy had it happen from near new https://mirageforum.com/forum/showth...exhaust-hanger

[Mark]

I remember before there was an issue with harmonic vibration from the exhaust, I feel my car experiences this while in an incline and light pedal tap. Does anyone experience this?

I feel like my 2017 Mirage has started to vibrate at low speeds this winter. I haven't crawled under it to check it out yet. I will be doing an oil change some time soon, & I will most likely investigate it better then. I suspect it's my exhaust hanger.

My 2011 Forester has been vibrating for two years @ low speed. I suspect a loose heat shield for that one. It's also 11 years old now. The heat shield rusted loose on my 2000 Honda CR-V, too! I just crawled under, yanked it off, & tossed it eventually. Problem solved!

[george]

I get a resonance/harmonic at "exactly" 2.5RPM, mostly in lower speeds. It's like a thin metallic sound. Used to be much louder at the beggining, now at around 13000kms, still occasionally hearing it. I was at the dealer, assured that there was nothing wrong and they'll check it again at the next service. They said it was the heatshield of the exhaust or something. Due for service in 2000kms, will check again with them. So far so good, no issues related to the sound, but it's annoying as hell, seeing it's a new car.

[foama]

@ george:

Had exactly the same problem which developed last year. Since it peaked at highway speed, it was most annoying.

After many hours searching, I found the cause. The rear part of the exhaust, being the piece after the main muffler through the resonance damper and all the way to the end was resonating, just as you explained.
To get rid of it, I cut the resonating pipe in the middle, inserted two hook-type fins, and reconnected the splice with a pipe connector. The annoying resonance is now totally gone. If you want, I could post a picture.

[Mark]

@ george:

Had exactly the same problem which developed last year. Since it peaked at highway speed, it was most annoying.

After many hours searching, I found the cause. The rear part of the exhaust, being the piece after the main muffler through the resonance damper and all the way to the end was resonating, just as you explained.
To get rid of it, I cut the resonating pipe in the middle, inserted two hook-type fins, and reconnected the splice with a pipe connector. The annoying resonance is now totally gone. If you want, I could post a picture.

I would like to see a pic of that. Sounds like a great solution!

[george]

@ george:

Had exactly the same problem which developed last year. Since it peaked at highway speed, it was most annoying.

After many hours searching, I found the cause. The rear part of the exhaust, being the piece after the main muffler through the resonance damper and all the way to the end was resonating, just as you explained.
To get rid of it, I cut the resonating pipe in the middle, inserted two hook-type fins, and reconnected the splice with a pipe connector. The annoying resonance is now totally gone. If you want, I could post a picture.

If it's not an inconvenience for you. I'll eventually go to the delaer as to not void my warranty yet Thank you so much!

[foama]

I would like to see a pic of that. Sounds like a great solution!

Quote george:

I get a resonance/harmonic at "exactly" 2.5RPM, mostly in lower speeds.






The problem:
The resonance inside the exhaust developed over time and worsend. Around 2200-2700 revs, there was a constant "louder than at other revs" sort of noise from the exhaust, a resonance, and it got on my nerves because it was very annoying and constantly there at normal highway speeds. The lower part of the exhaust, that is the pipe section after the main muffler was found to be resonating.


To cure the problem:
1.) The exhaust pipe was cut with a hacksaw about 30cm (1 foot) before the curve leading to the second hanger. This cut the exhaust in two. The rear section was then removed for modification.
See lowest picture.


2.) The pipe leading to the rear was cut with a hacksaw, producing a total of four slits in two pairs. Each slit cut about the depth of a regular hacksaw blade. Each pair of slits about the width of the hacksaw blade apart. See pictures.





3.) The slits were bent backwards in direction of the exhaust gasses passing. The angle of the two "fins" is about 30° measured from the uncut wall of the pipe.
See pictures.






4.) The exhaust was reinstalled, with the help of a normal aftermarket exhaustpipe connector of correct size. Finished! See picture below as it was laying ready for installation.





The resonance was aggravating at normal highway speeds but is now gone! The "fins" that were added are bent in the direction of the exhaust gasses passing, about at 30°. They let the exhaust gas pass with very little obstruction. In case of resonance developing, the resonating gas will change direction of travel and go back and forth during resonance. The fins are an obstruction for those gasses going in the wrong direction, thus no resonance occures any more.