Noice level advice - failed by 5db

[Salisburytree]

Evening all,

I was turned away from thruxton today for producing 95db, had a feeling I wasent going to get on track prior so wasent too bad of news to take!

However I'm abit puzzled... I tested 95 , stuck a jetex 4inch silencer on the end, retested and still 95db. What could have gone wrong there and what's my best move in terms of shifting the 5db , ideally getting to around 85 if achievable.

M54 engine, straight through 3 inch which already has a jetex decibel insert (the silencer was ment to be my back up!)

Thanks in advance!

Unfortunately I can't edit the title ... noiSe level!

[brillomaster]

Do you need the straight through exhaust? Obviously the best way to make the car quieter is reinstall the standard back box. That might be enough, if not, reinstall cats too.

Surely it wouldn't be that hard to get a secondhand back box, ideally, the one you kept in your garage, hopefully...?

But I do sympathise... I've accepted that I'm never doing a day at thruxton with my silly loud exhaust on my boxster. I foolishly binned my original exhaust,which I regretted about a week later, sigh...

[E-bmw]

Several years ago I did a home made straight through centre/rear section for my M52 it was diabolically loud (can't remember the actual Db) I then tried a side-by-side pair in a split section where the rear silencer is hoping it would make a difference enough to keep tracking (I already did with an M3 full system) however the difference was minimal and they were each around 20" x 5".

What I am saying is, I am not surprised an add-on didn't do enough for you.

I am pretty certain as a minimum you will need cats, a centre resonator & some form of back-box.

Yes, I know these are all heavy which you don't want, but it is either that or you won't get out on track.

If you are doing it yourself, these sound meters you can get for not very much on ebay are actually pretty accurate as I found out at the time.

https://www.ebay.co.uk/itm/197435395445?_skw=sound...

[SpudLink]

If all else fails, look for a 105db trackday. They may not do any at Thruxton, but several other UK circuits do.

[brillomaster]

95db static will be fine at most tracks, apart from the quiet ones, which are really only thruxton and goodwood.

So, if you live on the south coast, either refit a proper exhaust, or be prepared to travel!

[Salisburytree]

My objective is to reduce back pressure so I will be doing my best to avoid putting a cat on. Certainly need to get a back box / silencer on the go. The factory exhaust is at 2.5" so will need to source a 3" unit.. I guess that's the point I'm at would be recommendations on silencer brands please.

When I was at track I noticed the other e46 was running a 2f-3ft long silencer parallel to the rear end. So a right angle turn at the end of the straight pipe. He clocked in at 87db which was impressive for an m3

Thruxton is 15 minutes from me so it make sence to do the work and stay local...fastest track after all!

Edited by Salisburytree on Thursday 16th October 18:11

[fttm]

Many moons ago I ran a 2L 16v 205Gti with a side exhaust , this would regularly fail noise test at tracks , I made up a steel wool "tampon" on a piece of wire which was held in place with a grub screw , easily removed in a matter of seconds after testing . Bit agricultural but it worked .

[brillomaster]

You'll be needing something like these...
[url]

|https://forums-images.pistonheads.com/320571/202509147695415[/url]
[/quote]

But those look idiotic, just put the silencers under the car like a sane person.


But seriously, a track car is a bit pointless if it's too loud to go on track. I'd accept a slightly slower car if it meant I could actually use it. Also, since trackdays aren't racing, it really doesn't matter how fast your car is...