Quietest back box and / or centre with good flow?
02 January 2004, 09:19 PM
#1
Current state of exhaust system is now,erm, too loud and noticeable!
What is the best way to retain good flow but quieten the idle / part throttle exhaust sounds?
Resonated or silenced centre, or a quiet back box?
With just a Scoobysport/H&S back box, was a fair bit louder but with the fabled off beat rumble.
Not a lot of change going to a Scoobysport decat centre, just a bit louder and crisper.
Then, a H&S downpipe with splitter, and much louder, with more crackle and crisp sound, with pops and bangs on lift off / over run ( Forge recirc BOV used ).
Now, had OBX equal length headers fitted, ( and apart from a possible leak on turbo / up-pipe or downpipe ) the sound is louder again. As expected the note has changed, crisp bark on any throttle at all.
But the whole combination is too loud / draws too much attention in the villages and housing areas I have to drive through. Also very loud inside - I have a WRX wagon with the paper thin carpets and roller blind rear parcel shelf so little insulation!
What is the best way to retain good flow but quieten the idle / part throttle exhaust sounds?
Resonated or silenced centre, or a quiet back box?
With just a Scoobysport/H&S back box, was a fair bit louder but with the fabled off beat rumble.
Not a lot of change going to a Scoobysport decat centre, just a bit louder and crisper.
Then, a H&S downpipe with splitter, and much louder, with more crackle and crisp sound, with pops and bangs on lift off / over run ( Forge recirc BOV used ).
Now, had OBX equal length headers fitted, ( and apart from a possible leak on turbo / up-pipe or downpipe ) the sound is louder again. As expected the note has changed, crisp bark on any throttle at all.
But the whole combination is too loud / draws too much attention in the villages and housing areas I have to drive through. Also very loud inside - I have a WRX wagon with the paper thin carpets and roller blind rear parcel shelf so little insulation!
02 January 2004, 10:04 PM
#2
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Quieter backbox will make the biggest difference - e.g. MRT, Prodrive, remus, APS (Probably in that order, quietest first). Resonated centre will also help a bit.
02 January 2004, 10:18 PM
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I had the same prob, I fitted a resonated centre section to mine and it made a lot of difference. More than anything else it has taken away the raspy-ness and droning off it.
Plus she still pops and bangs like a good-un
I'm planning on going a bit further, it seems now that most of the noise is coming from the front of the car and not so much from the tail pipe, infact from the down pipe I reckon. A lot of people say they've had success with exhuast wrap, so I'm gonna whip the down pipe oooof and wrap it. May do it this weekend if I can find the enthusiasm
Plus she still pops and bangs like a good-un
I'm planning on going a bit further, it seems now that most of the noise is coming from the front of the car and not so much from the tail pipe, infact from the down pipe I reckon. A lot of people say they've had success with exhuast wrap, so I'm gonna whip the down pipe oooof and wrap it. May do it this weekend if I can find the enthusiasm
02 January 2004, 10:21 PM
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The simplest way to shut the thing up is with a backbox - the DP makes a lot of noise & you can't do much about that (except by using a mild steel DP, which there aren't very many of & then you would need to have it ceramic coated 
).
I was after a free-flowing quiet system, and there are very few of them around.
I don't know the MRT system, but suspect it's good 'cos the Aussies are big on sound levels (or lack of
).
The Prodrive & Remus systems are quiet - especially the Remus one - but both are restrictive, although that is relative and may not be a problem depending on how much power you have/are aiming for...
The APS system I have used & found to be very good, flow-wise and noise-level wise, but this was a complete system rather than just a backbox, and so not very useful for you at this point...
What I have ended up with, though, is a BPM ceramic-coated DP (excellent flow, quiet, full 3"), with a 'special' system made to order by H&S comprising of 3" centre with bubble silencer (a mini-silencer instead of a resonator, or indeed nothing), and a 3" (flow) backbox to the largest size they could cram in the space, packed with I-don't-know-what & tapering inside the 3" tailpipe to 2.5" with its own cutie little silencer in there as well . Works fantasticslly well.
The easiest way to keep things quiet is make the flow pipe as small as possible for the power requirements, and have as 'chubby' a silencer as possible in the space, while still keeping a straight-through system (the Remus, for instance, uses a baffle system which makes it very quiet but noticeably restrictive above ~6,000rpm on a ~270bhp car).
Hope something in there helps?
).I was after a free-flowing quiet system, and there are very few of them around.
I don't know the MRT system, but suspect it's good 'cos the Aussies are big on sound levels (or lack of
).The Prodrive & Remus systems are quiet - especially the Remus one - but both are restrictive, although that is relative and may not be a problem depending on how much power you have/are aiming for...
The APS system I have used & found to be very good, flow-wise and noise-level wise, but this was a complete system rather than just a backbox, and so not very useful for you at this point...
What I have ended up with, though, is a BPM ceramic-coated DP (excellent flow, quiet, full 3"), with a 'special' system made to order by H&S comprising of 3" centre with bubble silencer (a mini-silencer instead of a resonator, or indeed nothing
), and a 3" (flow) backbox to the largest size they could cram in the space, packed with I-don't-know-what & tapering inside the 3" tailpipe to 2.5" with its own cutie little silencer in there as well . Works fantasticslly well.The easiest way to keep things quiet is make the flow pipe as small as possible for the power requirements, and have as 'chubby' a silencer as possible in the space, while still keeping a straight-through system (the Remus, for instance, uses a baffle system which makes it very quiet but noticeably restrictive above ~6,000rpm on a ~270bhp car).
Hope something in there helps?
02 January 2004, 10:22 PM
#5
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Oh - exhaust wrap makes no difference on the DP IMHO.
But that's only IMO
What makes a bigger difference is making sure that all the grommets that are meant to be in the bulkhead are indeed still in the bulkhead
But that's only IMO
What makes a bigger difference is making sure that all the grommets that are meant to be in the bulkhead are indeed still in the bulkhead
02 January 2004, 10:24 PM
#6
Cheers guys!
Bit of both options!
FYI the downpipe is lagged, I changed headers as loads of noise from under rear of engine, was either up-pipe flexi failed or up-pipe to turbo gasket gone. Took the opportunity to change to tubular headers!! But seem to have a hiss on throttle open / load that I am told is likely to be a gasket leak ( blow or suck I don't know!! ). Getting sorted soon with clutch change.
Cheers.
Any more options folks?
Bit of both options!
FYI the downpipe is lagged, I changed headers as loads of noise from under rear of engine, was either up-pipe flexi failed or up-pipe to turbo gasket gone. Took the opportunity to change to tubular headers!! But seem to have a hiss on throttle open / load that I am told is likely to be a gasket leak ( blow or suck I don't know!! ). Getting sorted soon with clutch change.
Cheers.
Any more options folks?
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