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Discussion Starter · #1 ·
Hey all,

My 2013 Focus ST is running with Cobb Stage 3 gear at this point. I have the Cobb Turbo-back Exhaust (downpipe with catted exhaust). I initially thought that the Cobb exhaust was way too loud shortly after first driving my car after the installation. I then realized, it isn't so much the loudness, but rather the frequency of the exhaust that's my issue. I have a phone app that measures the decibel levels in the car, and the exhaust isn't any louder than like 75 db.

There is a noticeable drone cruising at 60-80 mph on the highway. If I give it some gas in 5th or 6th, not even wide open throttle, there is almost a sound boom reverberating through the cabin. It's very unpleasant to the ear. My wife, who is a musician (I am tone def), said that it sounds like there is something in the mid-low frequency of the sound that makes it uncomfortable to the ear.

Has anyone ever experienced this? Could it be vibrations? I believe that shop that installed the exhaust re-used the OEM exhaust mounts. I am not sure if upgrading to the Cobb mounts would do anything for the sound. Should I consider adding a resonator? Any recommendations?
 

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sounds exactly like typical aftermarket exhaust drone to me. this is one of the reasons that the manufactures choose to make the OEM exhaust system fairly quiet and then adding the sound symposer system to pump more noise back in to the cabin, also they can control when it allows more sound into the cabin.

as you start to remove all of the noise reducing devices the engineers design into their OEM systems to keep them quiet, the exhaust gets louder and louder. typically, the louder the system is, the more drone there will be. this is why some systems have bigger resonators/mufflers or some even have extra chambers or branches added to them to cancel out droning at certain frequency's.
 

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it also has to do with being a 3" exhaust vs a 2.5". This is why I went with the mountune which keeps it at 2.5" to help reduce drone and unwanted noise.
 

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It's a 3" exhaust with token resonators. I say token as they are small enough to barely make it better than straight piping. There is a reason if you search focus st cobb exhaust the suggested search options try to add in "too loud" and "drone".

You can make 3" exhausts not drone but you'll need a bit more silencing than what the cobb offers. Look at the Milltek exhaust for a perfect example of this.
 

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Discussion Starter · #5 · (Edited)
Thanks all!

I probably should have done better research originally. I read a few reviews of the Cobb exhaust, like this one, http://blog.modbargains.com/long-term-review-cobb-cat-back-exhaust-focus-st-steve-e/. The reviewer seems to say little to no drone. I sought advise from my shop as well, but I think that they are used to much much louder cars, so the Cobb is nothing in comparison. Also, the youtube clips don't really relay the amount or type of noise very well. The exhaust does sound great in my opinion, it's just that its certain frequencies are very annoying. I guess the downpipe could be adding to my problem as well.

I am new to this mod game. Those of you that have been through this before, would you rip out the Cobb exhaust and get something else? I'd have to sell it and see if I can get some money back. I'd then go with something like the Miltek or Mountune option that others have suggested.

Or would you add a resonator to the Cobb exhaust? I also noticed that the ST has virtually no sound insulation in the cargo area. Under the spare, there is bare metal. I am thinking of adding some sound deadening stuff, like Dynamat or Noico stuff.

thanks again all!
 

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Thanks all!

I probably should have done better research originally. I read a few reviews of the Cobb exhaust, like this one, Long Term Review: Cobb Cat-Back Exhaust for Focus ST 591100 by Steve E ? ModBargains.com's Blog. The reviewer seems to say little to no drone. I sought advise from my shop as well, but I think that they are used to much much louder cars, so the Cobb is nothing in comparison. Also, the youtube clips don't really relay the amount or type of noise very well. The exhaust does sound great in my opinion, it's just that its certain frequencies are very annoying. I guess the downpipe could be adding to my problem as well.

I am new to this mod game. Those of you that have been through this before, would you rip out the Cobb exhaust and get something else? I'd have to sell it and see if I can get some money back. I'd then go with something like the Miltek or Mountune option that others have suggested.

Or would you add a resonator to the Cobb exhaust? I also noticed that the ST has virtually no sound insulation in the cargo area. Under the spare, there is bare metal. I am thinking of adding some sound deadening stuff, like Dynamat or Noico stuff.

thanks again all!
This is my opinion, but if you do not like the sound it really depends on how much you drive it and how much you really do not like it to determine if you want to buy something else. I do not recommend you modify or add anything to the cobb exhaust because if whatever you do to it does not solve your sound problem, any worth you could have gotten selling it as a used cobb cat back would be out the window.

Also adding stuff like dynomat will help noise in the cabin, but typically wont do enough to change the drone. Ive been in cars that were fully built up, and even with 1200$ worth of dynomat on every square inch of cabin if the exhaust drones...you will hear it. I had a first gen SPL loudmouth on my mustang cobra...and it droned bad at multiple RPM ranges. I tried a few tricks with some high temp exhaust wrap in spots i could feel the exhaust resonate, it helped, but in the end i swapped it out for something else.
 

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I wouldn't bother throwing more money at the problem. Years ago I bought a new '99 Honda Prelude. It was very quiet so I bought a Borla axle back exhaust, and despite adding insulation in the trunk everywhere I could put it, it still droned. If I were you, I'd take it off, sell it on ebay and try again.
 

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LOL! Sorry, I had to chuckle out loud. This is a pretty common complaint and widely known. A 3" exhaust gains you little over a 2.5 inch, and the consensus appears to be that they generally have more drone than the 2.5" systems. Knowing this, and having heard a fellow enthusiast's FoST with stock exhaust with a resonator delete, I deleted the resonator and have been very happy. Fixes for a droning 3" system; add another muffler or resonator, or add a "J-pipe" towards the rear of the system. Personally, if you still have the stock system you could slap on there I would rock that with a resonator delete.
Oh, dang, almost forgot. If you haven't already disabled the sound symposer you should definitely try that. That might be one reason yours is so loud when accelerating in the "Drone range." The symposer adds sound to the already loud off throttle drone.
Hope that helps.
 

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....If I were you, I'd take it off, sell it on ebay and try again.
This!!

If you don't like it or can't live with it, for the love of all that's right in his world, PLEASE DONT go hacking on that gorgeous exhaust system! Just pull it and sell it before you head down bat road.

I don't know if mine calmed down, I adjusted, or just grew to love it, but 5,800 miles on mine now and I'm quite happy.
 
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