Need to find a solution for trackday noise. My exhaust is massive (with a cat to help noise) and there's no room to fit a bigger one, so looking at additional bolt-on bits.

I've tried a bung with wire-wool, which is a bit of a crappy solution but does get me just-about OK for most tracks.

Looking at this now (to bolt in the end of my existing exhaust):

http://www.demon-tweeks.co.uk/motorsport/universal-exhaust-silencers/jetex-universal-exhaust-silencer

anyone got any experience with these? Or suggest similar bolt-on alternatives?

Is it defo exhaust noise that is your concern not intake?

I have a "motor cycle insert baffle" Will try to get the details, find the receipt etc. Brought it down to the legal bit for Castle Coombe but does knock the performance some what.

quote:

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Originally posted by loggyboy
Is it defo exhaust noise that is your concern not intake?

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Fit a turbo!!

Had the same problems before my self,

So put on the extra silencer on the rear more permanent solution


rear exit exhaust

I've got one of these on my car:

http://www.carbuildersolutions.com/uk/6-stainless-steel-silencer

Trackday at Snetterton, 97static and drove round all day without issue.

Next trackday was a wet one at brands hatch, I missed the morning noise test as I was late but then drove round slowly all morning without issue. In the afternoon a dry line appeared and I was blackflagged for noise after 1 "hot" lap out of the pits.


£80 later i'd bought an exhaust bung from the trackside shop. One of these:

http://www.demon-tweeks.co.uk/Product.do?method=view&n=1884&p=446389&d=124&c=4&l=2&utm_source=Google&utm_medium=Base&u tm_campaign=Universal%20Exhaust%20Silencers&gclid=Cj0KEQiAsZayBRCrioKRkYetvc0BEiQAI70-A3NfhxYafuGYeiLHVsY2rDms4LnSmWiRgsGNfASHYEEaAqoV8P8HAQ

Static noise was recorded at 100! I was able to continue the day though, I drove round as I normally would and didn't trip any meters. 1st time I've googled to see if I could find the bung and it mentions no reduction in power. I'm dubious.

Conclusion, there's no logic to noise. If you're close to being "loud" somedays you'll be fine and other day's you'll be noisy. Do the best you can and also carry a bung.

I bought some DB killers from Furore for my IVA and my Rover V8 with no cats and 5 inch mufflers sailed through at a tiny 92Db. I am not sure what the do to BHP though. They came straight from Furore but I have curved them to fit up the curved exhaust. I don't need them now so they are available for small amounts of cash. U2U if interested.

quote:

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Originally posted by INDY BIRD
Had the same problems before my self,

So put on the extra silencer on the rear more permanent solution

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You need to take it out the back really, mine failed however if I stood between the outlet and engine the noise dropped by 3db

Cut 3 1/2" hole in front of the wheel, under the arch


Under arch

Then another facing the rear wish bones close to the diff as less movement

Use very tight mandal bends, then a kink so it fits nicely between the bone and half shaft


under halfshaft


through bulkhead

Box in behind the seat


bulkhead box

Then out the back


Exhaust rear , made life hard for myself with 3" exhaust all through.

Some people follow the curve under the wheel arch.

HTH





[Edited on 13/11/15 by mark chandler]

I solved my noise issues by (now) using a tired MX5 as a track hack. No more black flags, worries or NIMBY crap.

However, I did have some limited success on competition days (with the BEC) using a Merlin Motorsport bolt-on. Wasn't a great deal quieter with the thing on the tailpipe, but sank the static noise to just over 106 dB to just under 105 dB - so I could go and play at Combe - just.

I'm in a similar boat - black flagged at Oulton and used a bung and short-shifting to carry on. I've tried a variety of the cheap perforated bungs and they all only seem to take off a db or two. I've got large wunoff silencers on but it's still much louder than I'd expected, given only 1.5L per exhaust.
Wondering about the decibel devil next - bit more of an investment but if it makes the problem go away I won't mind.
Decibel Devil Race & Trackday Car Exhaust Noise Reducer Fits 3" O/D Tailpipes

quote:

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Originally posted by The Black Flash
I'm in a similar boat - black flagged at Oulton and used a bung and short-shifting to carry on. I've tried a variety of the cheap perforated bungs and they all only seem to take off a db or two. I've got large wunoff silencers on but it's still much louder than I'd expected, given only 1.5L per exhaust.
Wondering about the decibel devil next - bit more of an investment but if it makes the problem go away I won't mind.
Decibel Devil Race & Trackday Car Exhaust Noise Reducer Fits 3" O/D Tailpipes

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Have you tried re-packing your exhaust?

You may need to cut it open and re-weld if it's not a re-packable one.

Before I did mine the in-laws could here me coming over the moors 5 miles away!! now they don't hear me turn up!

I used acousta-fil (the figures on how much you need are miles out, you need much less!)

quote:

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Originally posted by rodgling

quote:

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Originally posted by The Black Flash
I'm in a similar boat - black flagged at Oulton and used a bung and short-shifting to carry on. I've tried a variety of the cheap perforated bungs and they all only seem to take off a db or two. I've got large wunoff silencers on but it's still much louder than I'd expected, given only 1.5L per exhaust.
Wondering about the decibel devil next - bit more of an investment but if it makes the problem go away I won't mind.
Decibel Devil Race & Trackday Car Exhaust Noise Reducer Fits 3" O/D Tailpipes

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Yeah, my thoughts exactly. I've also tried various bungs, none hugely successful. Looked at some reviews of the Decibel Devil: "Failed with 108db. Fitted decibel devil and passed with 103db" and elsewhere, "Supercharged XJS. Drive by noise was reduced from 106DB to 96DB", also "exhaust system is 108dbs at 6000rpm he did get black flagged once when he got caught up in traffic, but apart from that managed to run all day [98 driveby]"

Sounds worth a punt, could you buy one and let me know how you get on :-)?

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quote:

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Originally posted by The Black Flash
I would, trouble is, I need 2 :-/
I'll have to do something come the new year though.

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That'd be really good to know, I'm sure it'll save several of us either time or money, or perhaps both!

I fitted a homemade Supertrapp type thingy to clamp to my tailpipe
I had a local fab shop punch out a pile of thin washers out of sheet metal, and one with no centre hole. I then punched two holes in the edge of each washer at opposite sides and poked a 3mm rod through each one I then tack-welded each washer to the rods leaving a 1mm gap between each one. Then I made an outer tube to enclose it all and clamped it to the tailpipe.
It reduced my car from 104bd to 95db. Eventually, it fell off and I drove over it.

Static noise testing does my head in!

My car is pretty quiet on track, never triggered a drive by.

My car is pretty noisey on a static test, without tinkering almost guaranteed to fail a static test.

I put it down to at around 3/4 revs it must be the worst possible engine speed for vibrations to rattle the wafer thin bodywork, metal floor, dunno but whatever it is the meter don't like it.

I did ask at Cadwell last year if they could move the probe towards the front of the car just to see what happened, the reading increased as they moved forward then decreased again from about 3/4 way forward until they got to the very front where it increased again, the intake for the enclosed air box is behind the nose cone grill in front of the radiator.

The annoying thing is like I have mentioned once on track it's like a mouse compared to most trouble is Oulton for example won't let you out without passing a static test, Cadwell on the other hand (same 105) is a doddle.

Is your exhaust re packabke? Acustafil seems to work best for me and my Oulton static test washer, I have a butterfly like a throttle in the pipe, turn it to all but block the exhaust for test, open it back up once passed.

I replaced the link pipe between the collector and silencer with another small silencer. I had it made with 2" OD end pipes so it would slip inside the collector and the main silencer. It was 5" long and took exhaust noise down by 5dB from 103 to a more bearable 97dB. Performance wasn't affected at all so it became a permanent fixture.


advertpic1

quote:

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Originally posted by owelly
I fitted a homemade Supertrapp type thingy to clamp to my tailpipe
I had a local fab shop punch out a pile of thin washers out of sheet metal, and one with no centre hole. I then punched two holes in the edge of each washer at opposite sides and poked a 3mm rod through each one I then tack-welded each washer to the rods leaving a 1mm gap between each one. Then I made an outer tube to enclose it all and clamped it to the tailpipe.
It reduced my car from 104bd to 95db. Eventually, it fell off and I drove over it.

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You can add/remove the discs to suit. Mine worked very well.

quote:

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Originally posted by mark chandler
You need to take it out the back really...

Exhaust rear

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Try repacing the silencer using Acustafil material, managed to lower my db level 4decibels

We fit one of these when we have to on track days, brings static down by about 5dbls. Problem is now the intake..
http://www.custom-chrome.co.uk/Track-Comp-Boxes.html

quote:

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Originally posted by Fcck2000
We fit one of these when we have to on track days, brings static down by about 5dbls.

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I can't remember exactly. I seem to remember it had a perforated smaller section inside which adjusted the direction of the gasses towards the outer packed area. It definitely works. We tested with our phone dbs sensor before and after and it gave 4/5 dbs reduction.
The guys at Custom Chrome were really helpful, we failed the noise test at Mallory and gave them a call in the morning (9am) to see what they could do for us at short notice. We gave them our exhaust sizes over the phone and collected it at 11am, it was still hot from the welding. Went back to Mallory and passed the noise test after we also baffled the intake with some welding mat which Custom Chrome also donated to us.

quote:

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Originally posted by rodgling

quote:

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Originally posted by The Black Flash
I would, trouble is, I need 2 :-/
I'll have to do something come the new year though.

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I'm going to do Snetterton in a few weeks, will do noise test with and without one of these fitted and let you know how much improvement I get.

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quote:

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Originally posted by The Black Flash

quote:

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Originally posted by rodgling

quote:

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Originally posted by The Black Flash
I would, trouble is, I need 2 :-/
I'll have to do something come the new year though.

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I'm going to do Snetterton in a few weeks, will do noise test with and without one of these fitted and let you know how much improvement I get.

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Soooo, did you find anything out?

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Soooo, having booked in at Croft for the 20th, I took the plunge and bought a pair of decibel devils.
Tested with my home noise meter at 50cm, 45 degrees from one of the outlets:

Without Decibel Devil:
104.0
106.1 (!)
104.5

With Decibel Devil
101.2
101.2
102.3

I think that the 106 was an outlier as I blipped it a bit. Anyway, looks like a solid ~3db reduction there.
It's also clear that wrapping the headers has made the thing much noisier, it was 102 last year before I wrapped it. I will see how it goes on track this time and perhaps remove the wraps if I think I can get away with it.

In the interest of science, I also tried it with a large metal disk 1" in front of the outlet - I thought that this might reduce the sound waves going outwards. Results were interesting:

With Disk:
104.2
101.7
102.1

Seemed to make things worse. I then tried moving the sound meter so that it was head on to the exhaust pipe, rather than at 45 degrees. Only two readings as I didn't want to annoy the neighbours more than I already had!

With decibel devil, head on, no disk: 101.3
With decibel devil, head on, with disk: 100.00

So, the disk *may* improve the situation directly behind the exhaust, but not at an angle, in fact may make it worse. I was interested that the reading without the disk was the same head on and at 45 degrees.

I've had to modify them a little to increase the length of the straps, to fit into my curved exhaust - just welded on an extension. Other than that, they seem to do the job. Hopefully that's useful to some.

Thanks, that is good to know. My current plan is to make up a baffle from a rod and some semi-circles welded on like so (side view):

___|___ ____
|

which I can shove up my straight-through exhaust, as an additional option to the Decibel Devil. Will see how that works out.

I've also since found that all of the wadding had gone from one of the silencers, and half of it from the other. I'm going to blame the fact that I wrapped the headers making the silencers get too hot.
Repacking them with acousta-fil so hopefully shouldn't have problems in future.

I tried the DD at Snetterton recently. I just about scraped through once I'd stuffed it full of scouring pads, but I think they were being generous because I'd made the effort to fit a bung.

So, go big or go home - I got this made:



which attaches to the side can and runs under the suspension to sit under the fuel tank. It's removable for road use, hopefully the limited ground clearance (about 70 mm) will be OK on track.

Static noise has dropped from about 102 dB at 4500 rpm down to around 95 dB, very happy with that.

[Edited on 16/7/16 by rodgling]