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Registered
2006 FSTi Manual
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68 Posts
Discussion Starter · #1 ·
After a month or so of running the FSTi I’m wondering if there’s a way of reducing the amount of noise that the exhaust seems to generate. It’s the 3” Milltek and at motorway speeds the resonant drone is a bit too loud for family trips. One of these little DB apps measured it at about 90db in the cabin which is a bit excessive with a kiddie in the back.

Road noise isn’t too bad but it’s the ‘thrumm’ of the exhaust that seems to invade the cabin…

So, what can I do to turn down the volume? Will a different exhaust system / section sort it out? What about one of these track day bungs?
 

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2006 STI
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6,972 Posts
Different system is probably the right solution, although I believe someone (possibly Forester Gump) managed to reduce the noise intrusion by "filling" a gap in the boot.

I am pretty sure fpan got fed up with his Miltek for similar reasons.

My car is very quiet. Standard all the way through with a Prodrive backbox. I believe Scratch has almost the same set up, only has lost the cat in the centre section. His is a little louder than mine, but he is happy that it is non-intrusive on a run with the family, so that sounds just what you're after.

Might be worth a search on here to see more details about those cases and what other solutions people plumped for.
 

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Premium Member
2005 xt magic wand
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4,072 Posts
iirc milltek is 3" right through with the cat in the lower section of the front pipe, go to 2.5" with a resonated centre. should keep it reasonably sane!
 

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Registered
2004 looking 6 MT
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262 Posts
I replaced my 3" back box with an STI Genome item which is 2.5".Much quieter off boost and it does'nt drone when on the motorway.Sounds great actually when being enthusiastic.
 

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MY05 Forester 2.5 XT 5MT
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3,002 Posts
I run an 80mm Tomei catback system, no resonator (It's JDM so in metric) It came with an exhaust bung and I have tried fitting it. It seemed to lose a bit of "pull" but it was much quieter, I was quite surprised by the effect the bung had but they do work. So that might be a good short term solution for you I guess?..........Longer term, maybe look at changing systems?
 

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01 UK S-Turbo AT
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1,556 Posts
You could add an additional resonator in the middle section. I added two in the end as mine ws just too loud without them. I'm not sure if adding a resonator will reduce the drone inside the cabin as the frequency at which it resonates may remain unchanged!

Bassmaker might know...?

Mike


Sent from AutoGuide.com App
 

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2005 forester sti 6 speed manual
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428 Posts
miltek do a resonator box in the down pipe and sport cat in the centre section(as per mine making it about the queitest 3" system you can buy) so if yours is the same and is still too loud then new exhaust is probably the best idea(2.5" backbox modified to fit may work but don't quote me as i'm not paying).maybe heat lag the centre pipe also.
 

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Mr. November 2008
2015 BMW 335d xDrive GT Auto
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969 Posts
Mine droned on the motorway, but most of the noise comes in through the vent that's down to the left of the liftable boot floor inserts. Having established that stuffing an old towel into that cavity reduces the noise I then wadded some old carpet underlay in there.

Then Dynamat around the spare wheel cavity, wherever it goes 'bong' when you rap it with your knuckles. If it goes 'bink' it is ok.

Likewise some Dynamat and some foam inside the rear hatch cavities.

Much much quieter!
 

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Mr. November 2008
2015 BMW 335d xDrive GT Auto
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969 Posts
Aha!

I knew someone had done that with positive results!
The other thing that had a very positive noise reduction was taking an old mattress to the dump. It seemed to soak up the noise. So if you've got the space then filling the car with old mattresses really does the trick :icon_cool:
 

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2006 FSTi Manual
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68 Posts
Discussion Starter · #11 ·
Mine droned on the motorway, but most of the noise comes in through the vent that's down to the left of the liftable boot floor inserts. Having established that stuffing an old towel into that cavity reduces the noise I then wadded some old carpet underlay in there.

Then Dynamat around the spare wheel cavity, wherever it goes 'bong' when you rap it with your knuckles. If it goes 'bink' it is ok.

Likewise some Dynamat and some foam inside the rear hatch cavities.

Much much quieter!
I'll take a look at this when I get home today - thank you all for your input. I'll try this first and let you know how I get on.
 

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Registered
2007 EDM FXT 4EAT ST3 Automatic
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441 Posts
Remap it. You can alter the sound by tuning the overlap (avcs) in the cruise areas.

Much easier and cheaper than doing hardware mods. No guarantee it'll work, but it's worth a try imho.

Of course driving with a mattress is even easier.

:)
 
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