Exhaust noise limits?

Slothie · Post by **Slothie** » Mon Jul 23, 2007 1:24 pm

Are there any limits on noise levels from cars & trikes? I know there are for motorbikes - and does anyone know what applies to Q plated vehicles?? I've been looking around on t'net and can't find anything other than people saying "I dont think there are"... Any MOT savvy people lurking here?

Post by **katanaman** » Mon Jul 23, 2007 2:11 pm

Noise levels at an MOT are subjective at best and unless its really noisy they have no way of failing you. If you need an SVA then that's a whole other story and you will have to comply with it. All that said and done you still have the construction and use regs which does have a limit and this is enforced by the police. They will pull you and they will impound your trike if its too noisy and you ignore them. It also depends on what your trike is classed as, you get car derived tricycle (reliant robin) and bike derived. Not sure if the bike derived still needs a BS stamp on the silencer to prove it complies. What the actual limits are I have no idea but keep it sensible and you should get away with it.

Paul B · Post by **Paul B** » Mon Jul 23, 2007 3:37 pm

Slothie wrote:Are there any limits on noise levels from cars & trikes? I know there are for motorbikes - and does anyone know what applies to Q plated vehicles?? I've been looking around on t'net and can't find anything other than people saying "I dont think there are"... Any MOT savvy people lurking here?

Use common sense here, don't make it too loud else you'll just pi$$ lots of people off.

There is a little scooter round where I live, with some sort of expansion pipe on, and the noise is just deafening, like a massive wasp, really offensive. What will happen is people will complain to the police, who will have to put a report in, and if enough reports are sent in then somebody somewhere will decide that 'motorbikes' are too noisy, and that will lead to new maximum noise levels being set in place for NEW bikes.

If you hear how silent a new bike is straight from the showroom you'll realise just how wrong something is with this system, but it is the few noisy vehicles who set the ball rolling with bringing in new government maximum noise levels.

Slothie · Post by **Slothie** » Mon Jul 23, 2007 4:35 pm

I'd imagine that the SVA limit (101dBA @ 0.5M/45deg) is the one that applies... That's pretty damn loud. I'm taking apart my silencers this week, so if I make sure all the paddings up to scratch, and the baffles are OK, then maybe I'll be OK!
I might borrow a meter and check it.....!

Slothie · Post by **Slothie** » Mon Jul 23, 2007 4:42 pm

Paul B wrote:Use common sense here, don't make it too loud else you'll just pi$$ lots of people off.

That's pretty much my motivation. I'm not really into "loud" as an end in itself, it's just with a V8 and an exhaust of total length of ~2m there's a limit to what I can do without getting a completely new system designed (which I'd consider, when I'm a bit richer..!)
So it looks like I'll be getting out the steel mesh and rockwool....

Post by **katanaman** » Mon Jul 23, 2007 7:22 pm

You will get better results going to a bike shop and buying the proper packing. It isn't expensive wont go on fire and is meant to do this job. An absorption baffle relies on the material and tube perforations for its effectiveness. It shouldn't be packed very tight either as its something to do with the movement of the fibres that reduces the exhaust noise (reverse sound waves cancelling each other out or something like that).

I once used steel wool for this on a bike. It was spectacular, completely useless but the red glow and flames was something to see lol.

5000SE · Post by **5000SE** » Mon Jul 23, 2007 7:40 pm

Slothie wrote:I'd imagine that the SVA limit (101dBA @ 0.5M/45deg) is the one that applies... That's pretty damn loud. I'm taking apart my silencers this week, so if I make sure all the paddings up to scratch, and the baffles are OK, then maybe I'll be OK!
I might borrow a meter and check it.....!

Actually, that's not very loud at all - and that's the level measured just half a metre from the exhaust pipe. A car horn is 120dB at one metre - and remember that the dB scale is logarithmic, so 103dB has twice the sound energy of 100dB.
100dBA is what you get on a tube tain, or at the peak levels of a classical concert.
Inside a busy pub, or city centre traffic is up to about 90.
Nighclubs/discos about 110, a loud rock concert can be 120.
At half a metre, loud open exhausts are way, way over 101dBA. Race circuits in the UK have varying noise limits, depending on their location and the event, but the variation is from 98 to 108 dBA.

Most bikes have to be below about 95dBA or thereabouts, but a standard 2007 Harley 1500 makes 97dBA at idle, 102dBA at cruising speed and 111dBA when revved. They're 'loud' but not damned loud!

mgbv8 · Post by **mgbv8** » Mon Jul 23, 2007 9:10 pm

The exhausts on my MGB V8 are Rv8 style headers opened out to 2.5 inches. With 2.5 inch pipes to the cheap RS turbo mufflers with the pipes coming out in front of the rear wheels.
Complete home brew system. When I took it for the last MOT, the guy issued a separate VOSA ticket to say it was a non standard exhaust, but it met the requirements of the MOT at time of testing. The MOT guy also happens to be a VW Beetle nut. And my twin system is not as ear splitting as the stinger on his Beetle.

Paul B · Post by **Paul B** » Mon Jul 23, 2007 9:55 pm

Slothie wrote:
Paul B wrote:Use common sense here, don't make it too loud else you'll just pi$$ lots of people off.
That's pretty much my motivation. I'm not really into "loud" as an end in itself, it's just with a V8 and an exhaust of total length of ~2m there's a limit to what I can do without getting a completely new system designed (which I'd consider, when I'm a bit richer..!)
So it looks like I'll be getting out the steel mesh and rockwool....

You should be able to plumb in some big back boxes off something else with no problem. I fitted two tiny boxes under my Morris, and that was too harsh/loud, so I fitted some 'Cherry bomb' style mufflers at the back and that makes it real mellow, even though they are straight through.

Check out www.jetex.com or whetever their site is called.

Post by **katanaman** » Mon Jul 23, 2007 10:01 pm

dont know what that link is supposed to go to but for me anyway it goes to a store on ebay selling ink cartridges.

The Original Tom · Post by **The Original Tom** » Tue Jul 24, 2007 11:43 am

When I did mine I made an anonymous call to the MOT centre and asked if they have a decibel meter - to which they answered no. Problem solved as they can't fail you if they "think it's too loud".

My stereo is 100dB@1M and that's loud! So loud that with the wondows open in a tunnel the engine can't be heard...
I'm sure mine's below the limit as plod haven't stopped me.

5000SE · Post by **5000SE** » Tue Jul 24, 2007 2:30 pm

The Original Tom wrote:When I did mine I made an anonymous call to the MOT centre and asked if they have a decibel meter - to which they answered no. Problem solved as they can't fail you if they "think it's too loud".

You might think so, but for motorcycle MOTs there is no measurement - the tester can fail a bike if it's too loud in the tester's judgement.

And they do fail them, because they fear losing their testing ticket if they let loud stuff pass.

I'd be very surprised if the same didn't apply to car MOTs. Turn up with open pipes on a big block and the tester who passes it will either be stupid or in a very good mood.

ihatesissycars · Post by **ihatesissycars** » Tue Jul 24, 2007 2:59 pm

I've worked in a motorbike shop and anything without a BS stamp on the pipe or even if it doesn but it sounds suspicious would fail everytime however I work in a car garage now and looooooooooooooads of cars with equally loud pipes pass.

Its just the trends in each business, loud pipes on bikes is very common so all the testers know whats legal and whats not whereas very few cars have loud pipes and when a tester does encounter one they often pass it as its not a common occurance and therefore aren't ever sure if its ok or not.

I don't think (although i may be wrong) that car exhausts have to have a bs stamp signifying compliance with noise regs wjhereas bike ones do, bike "race" pipes actually have to have "NOT FOR ROAD USE" or similar stamped on them.

Post by **katanaman** » Tue Jul 24, 2007 4:07 pm

Car exhausts don't need BS stamp but they do need to have effective silencing which is why I said it was subjective at best for an MOT. As of last year bike exhausts don't have to be BS marked either but if it has "not for road use" on it then its an instant fail. They had to pull the BS on bikes as they didn't have it for cars and couldn't think of an effective way to do it on cars. It was useless anyway as everyone I know just bought a £2 BS badge and riveted it on the exhaust. Didn't matter how loud the bike was then as you just argued it was BS stamped which was what the law needed. Lucky my bike is an EXUP so is pretty quiet on idle and low revs anyway. Doesn't half howl on full chat though.

mgbv8 · Post by **mgbv8** » Tue Jul 24, 2007 4:34 pm

Maybe thats why my tester gives me a separate ticket to say none standard exhaust, but met the requirments of the MOT at time of testing.
He doesnt know what you are going to do once you have the ticket does he.

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