Need to get below 105 dB.......
Discussion
With the car now pretty much finished and running well I am now turning my mind to next year. I have done a number of track days in previous cars and definitely need to get out there in the GTR. My nearest track is Castle Coombe, which is a 100 dB limit and most others seem to be 105dB.
Checked mine the other day and am nearer 110dB
(measured at about 45deg from the exhaust at the side of the car at 4500 rpm). I have std SBC up and over type exhaust that has probably been unchanged from new so expect most of the wadding to me either missing or turned to dust !
The question is if I modify the silencers to be repackable, and repack them regularly, is that alone gonna get me where I need to be....or do I need something more radical. Would like to know specific experiences out there. Do lots of folks do track days with the std exhaust set up or does everyone make mods. I plan to get system camcoated over the winter so want to make sure it is up to the job before I do so.
......I guess the other option is if anyone knows of track days with higher noise limits !
Thanks
Stu
Checked mine the other day and am nearer 110dB
(measured at about 45deg from the exhaust at the side of the car at 4500 rpm). I have std SBC up and over type exhaust that has probably been unchanged from new so expect most of the wadding to me either missing or turned to dust !The question is if I modify the silencers to be repackable, and repack them regularly, is that alone gonna get me where I need to be....or do I need something more radical. Would like to know specific experiences out there. Do lots of folks do track days with the std exhaust set up or does everyone make mods. I plan to get system camcoated over the winter so want to make sure it is up to the job before I do so.
......I guess the other option is if anyone knows of track days with higher noise limits !
Thanks
Stu
hi
i had the same problem 114db.
JP exhausts in Macclesfield fitted removable plates and repacked them and when tested it was 94db i think at 3k and 96 at 4k....cant remember but in a previous post... cost £100..... it burnt the wadding again in approx 500-1000 miles but considering i can now repack them i feel it was worth it....I also fitted the silencers so the plates were at the bottom so you cant see them, although to repack you have to take them off
Dom
i had the same problem 114db.
JP exhausts in Macclesfield fitted removable plates and repacked them and when tested it was 94db i think at 3k and 96 at 4k....cant remember but in a previous post... cost £100..... it burnt the wadding again in approx 500-1000 miles but considering i can now repack them i feel it was worth it....I also fitted the silencers so the plates were at the bottom so you cant see them, although to repack you have to take them off
Dom
mybrainhurts said:
How do you secure such plates....?
Some have used rivnuts.I welded a plate behind the skin with tapped holes for the fixings.
If you want to repack the Factory system you will need to open both sides of the box as you cannot change the packing from one side only.
Steve
This is my story. My first attempts I did 4 years ago, and are very similar to what Steve describes.
I cut access holes top and bottom, pulled the old stuff out (what was left) and repack (quite regularly as it happens) and reseal. First I used ally rivets, that was a mistake as they melted on track under heatsoak conditions. I then used stainless rivets, which last but are a bu66er to get out without enlarging the holes and thus making refitting difficult. My final solution is the same as Steves, welded in 5mm thick steel plates, with tapped holes to accept M6 button heads.
Repacking material has always been an issue, it all seems to burn away of turn to dust, but the stuff I use now does last a lot better (can't remember the source at the mo). Loft insulation turns to dust very quickly, good old fibre glass cloth works pretty well and I was getting loads of waste free, but it does disappear and you get ceramic lumps knocking around when bits of it melt.
The picture below shows the inside of the then standard box, still the same I have no idea:
Installed, with panel fitted:
Notice the balance pipe, that did not make any real difference to noise levels.
But, the best thing for noise reduction is this:
This box replaces the two bolt on tail pipes, has a built in cross over and angles the exit down at 45 or so degrees. Performance does not seem to be affected, as far as I can tell. Without at ~4000rpm trackday noise measurement at Bedford I was at 103dB, with the 3rd box I was well under 97dB for the static test. Drive by has never been an issue, nice low down rumble, not a screamer!
My 3rd box does fit behind a grill, but does not exit in the same place as the originals, one day I will cut the ends so the sit flush, but I only use this when necessary and now take it to all tracks days as a backup.
Hope this helps.
I cut access holes top and bottom, pulled the old stuff out (what was left) and repack (quite regularly as it happens) and reseal. First I used ally rivets, that was a mistake as they melted on track under heatsoak conditions. I then used stainless rivets, which last but are a bu66er to get out without enlarging the holes and thus making refitting difficult. My final solution is the same as Steves, welded in 5mm thick steel plates, with tapped holes to accept M6 button heads.
Repacking material has always been an issue, it all seems to burn away of turn to dust, but the stuff I use now does last a lot better (can't remember the source at the mo). Loft insulation turns to dust very quickly, good old fibre glass cloth works pretty well and I was getting loads of waste free, but it does disappear and you get ceramic lumps knocking around when bits of it melt.
The picture below shows the inside of the then standard box, still the same I have no idea:
Installed, with panel fitted:
Notice the balance pipe, that did not make any real difference to noise levels.
But, the best thing for noise reduction is this:
This box replaces the two bolt on tail pipes, has a built in cross over and angles the exit down at 45 or so degrees. Performance does not seem to be affected, as far as I can tell. Without at ~4000rpm trackday noise measurement at Bedford I was at 103dB, with the 3rd box I was well under 97dB for the static test. Drive by has never been an issue, nice low down rumble, not a screamer!
My 3rd box does fit behind a grill, but does not exit in the same place as the originals, one day I will cut the ends so the sit flush, but I only use this when necessary and now take it to all tracks days as a backup.
Hope this helps.
Hi Dom, I did some research about the position of the balance pipe. It seems there are a few theories out there. I seem to remember one being 18" from the collectors, so I put mine at the end of the first pass down the silencer, not ideal and I just wanted to try something. I have always wanted to get round to reworking the whole system and get rid of the standard silencers as they are very restrictive and do not allow much wadding around the perforated tubes.
don't people buy these from the factory?
more info when you scroll down...seems a easy fit to the standard pipes for most?
http://www.pistonheads.com/Gassing/topic.asp?h=0&a...
don't know if it helps though
more info when you scroll down...seems a easy fit to the standard pipes for most?
http://www.pistonheads.com/Gassing/topic.asp?h=0&a...
don't know if it helps though
Pb3 said:
Hi Dom, I did some research about the position of the balance pipe. It seems there are a few theories out there. I seem to remember one being 18" from the collectors, so I put mine at the end of the first pass down the silencer, not ideal and I just wanted to try something. I have always wanted to get round to reworking the whole system and get rid of the standard silencers as they are very restrictive and do not allow much wadding around the perforated tubes.
HiI have somewhere alot of research about the balance pipe and its pros and cons. The myth of added torque and reduced noise was very wide spred but differed from engine to engine.
The average gain was 4-7% ftlb torque increase and next to no noise measured difference but the exhaust note quite different in sound to the ear. Its critical where it goes..
If you want horsepower in the way of silencers use magnaflow , Ive cut and pasted part of an email of one of the conversations I had with Joe Sherman in the states last year.........
On Sun 09/11/14 19:57 , "Dominic Farley" dom.
> I hope you dont mind me emailing you, but I read
> a very interesting article on exhaust design where you
> were quoted as saying how good the magnaflows were on the dyno. Im
> after some info on exhaust design as im running a mid engined 383
> 550hp with a tuned header setup. The headers are tuned length 1
> 7/8 tubes going into 3 inches collectors and the muffler at the moment
> bolts straight onto them. there is then a 16 inches (3 inch
> diameter) tail pipe. Im trying to find a way to quieten it in the small
> space but not loose the horsepower and not sure if i should keep 3
> inches all the way or have 3inch in and 2.5 inch out to get some back
> pressure. The other idea I have is to have a y piece off each
> collector then have 2 magnaflow mufflers attatched to each collector
> so i end up having 4 muflers side by side splitting the 8 cylinders
> so 2 cylinders worth of gases go into each muffler(again not sure if i run 2 inch mufflers or 2.5 inch off the 'y'? If possible could you point me in the right direction, a book or an information site on the internet as these cars(ultima GTR)
> are restricted in space as to what we can do and i know the exhaust has a serious effect in the engines performance.
Many thanks in advance Dom>
Do you have room for a 6 inch round muffler ?? Magnaflow does make some of these . I use them for dyno testing all the time==It will only loose 5 HP on a 1000 HP BB Chevy engine. Joe>
As for the 4 silencers side by side Kyle is the man to ask as he tried it afterwards. Me as said before I bought my Db down way way low enough for track days but its all burnt away again now , but now its winter and all packed away.
Dom
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