mreguest
Member
Hello,
I have measured exhaust noise using a couple of different silencers in my 2.5" mongoose system. Tests were done by me using a professional type 1 sound level meter, so spectral frequency data is available and I'll make a nice graph one day when I get some spare time.
As per SVA, IVA and 70/157/EEC the measurements were undertaken at a distance of 0.5m from the exhaust pipe at 3/4 engine power etc...
As you will see in this document from 2009 imported car exhausts are not supposed to exceed 99dBA, and prior to 2009 I think the limit was 102dBA. I have not looked into whether this only applies at the time of import or if we are expected to comply with this as it gets stricter. I assume it would be completely unreasonable for us to comply with the new regulations...
http://www.minimag.co.uk/files/2011/08/M1-Inspection-Manual-May-09-1.pdf
I did the tests at 5625rpm and my car is standard boost & ecu fueling etc...
5-6 year old mongoose with decat pipe.
= 105dBA (f'ing loud)
mongoose with unknown age second hand (off bob) hks/mongoose decat silencer. - one of these:
http://www.ebay.co.uk/itm/Nissan-Sunny-Pulsar-GTiR-Mongoose-Decat-Pipe-/221210600200
= 98dBA (still loud but should comply with many track day noise tests)
mongoose with hks/mongoose decat silencer and my own 'custom bodge job' with additional 500mm Jetex silencer - one of these:
http://www.ebay.co.uk/itm/Jetex-Uni...-5-Mild-Steel-Case-Length-500mm-/290616387048
= 91dBA (much quieter, comparable to friends 15 year old knackered but standard Toyota MR2 exhaust)
At idle (~1000rpm) I got...
mongoose with decat pipe.
= 82dBA
mongoose with hks/mongoose decat silencer.
= 81dBA
mongoose with hks/mongoose decat silencer + my 500mm bodge.
= 74dBA
Note at idle the small silencer makes chuff all difference because of the frequency response. At idle there is not a great deal of higher frequency noise, so the silencer has nothing to work on and as such the dBA value is dominated by low frequency noise. As you rev up you generate more higher frequency noise which the silencer can attenuate. Due to its length the big silencer can attenuate noise quite well at most frequencies.
Obviously different peoples car will produce different noise levels/frequencies depending on the type of mods, tuning etc... but this gives you a good idea of what is possible.
Naturally as your exhaust gets older it also gets louder because the mineral wool packing material degrades over time.
I'll probably do a 'how-to' sometime documenting my bodge job fitting a 500mm silencer across the back of the car - i'm quite proud of it and it did not take any welding, just a grinder, bit of additional pipe, exhaust putty, hangers and clamps... these volvo clamps are really good for clamping and hanging:
http://www.ebay.co.uk/itm/Volvo-V70...st-Tailpipe-Bracket-Hanger-64mm-/360418504473
When I get some spare time I'm also going to document an experiment with some material that is very similar to Dynamat. See these three experiments on their website:
http://www.dynamat.com/technical_sound_dbates_intro.html
I hope to recreate these experiments at my work using my car as a demo and demonstrate the properties of some advanced (and should be cheaper and lighter) material that I hope to start selling... I can't wait to kill off lots of road noise and panel vibrations
Vroom Vroom!
Adam
I have measured exhaust noise using a couple of different silencers in my 2.5" mongoose system. Tests were done by me using a professional type 1 sound level meter, so spectral frequency data is available and I'll make a nice graph one day when I get some spare time.
As per SVA, IVA and 70/157/EEC the measurements were undertaken at a distance of 0.5m from the exhaust pipe at 3/4 engine power etc...
As you will see in this document from 2009 imported car exhausts are not supposed to exceed 99dBA, and prior to 2009 I think the limit was 102dBA. I have not looked into whether this only applies at the time of import or if we are expected to comply with this as it gets stricter. I assume it would be completely unreasonable for us to comply with the new regulations...
http://www.minimag.co.uk/files/2011/08/M1-Inspection-Manual-May-09-1.pdf
I did the tests at 5625rpm and my car is standard boost & ecu fueling etc...
5-6 year old mongoose with decat pipe.
= 105dBA (f'ing loud)
mongoose with unknown age second hand (off bob) hks/mongoose decat silencer. - one of these:
http://www.ebay.co.uk/itm/Nissan-Sunny-Pulsar-GTiR-Mongoose-Decat-Pipe-/221210600200
= 98dBA (still loud but should comply with many track day noise tests)
mongoose with hks/mongoose decat silencer and my own 'custom bodge job' with additional 500mm Jetex silencer - one of these:
http://www.ebay.co.uk/itm/Jetex-Uni...-5-Mild-Steel-Case-Length-500mm-/290616387048
= 91dBA (much quieter, comparable to friends 15 year old knackered but standard Toyota MR2 exhaust)
At idle (~1000rpm) I got...
mongoose with decat pipe.
= 82dBA
mongoose with hks/mongoose decat silencer.
= 81dBA
mongoose with hks/mongoose decat silencer + my 500mm bodge.
= 74dBA
Note at idle the small silencer makes chuff all difference because of the frequency response. At idle there is not a great deal of higher frequency noise, so the silencer has nothing to work on and as such the dBA value is dominated by low frequency noise. As you rev up you generate more higher frequency noise which the silencer can attenuate. Due to its length the big silencer can attenuate noise quite well at most frequencies.
Obviously different peoples car will produce different noise levels/frequencies depending on the type of mods, tuning etc... but this gives you a good idea of what is possible.
Naturally as your exhaust gets older it also gets louder because the mineral wool packing material degrades over time.
I'll probably do a 'how-to' sometime documenting my bodge job fitting a 500mm silencer across the back of the car - i'm quite proud of it and it did not take any welding, just a grinder, bit of additional pipe, exhaust putty, hangers and clamps... these volvo clamps are really good for clamping and hanging:
http://www.ebay.co.uk/itm/Volvo-V70...st-Tailpipe-Bracket-Hanger-64mm-/360418504473
When I get some spare time I'm also going to document an experiment with some material that is very similar to Dynamat. See these three experiments on their website:
http://www.dynamat.com/technical_sound_dbates_intro.html
I hope to recreate these experiments at my work using my car as a demo and demonstrate the properties of some advanced (and should be cheaper and lighter) material that I hope to start selling... I can't wait to kill off lots of road noise and panel vibrations
Vroom Vroom!
Adam