Devon TRF Group Forum

Pete · Devon's Best

Road Legal or Too Loud ?

Pearcy · Expert

How / where can we test our bikes to find out how loud they are?

My bike barks a bit when it is on full chat as they say, but it has a standard / road legal can.

I know this does NOT mean it is acceptable to people who don't like bikes and want total quiet, and in the nature of not wanting to upset people, I wondered where I could find out how loud my bike is?

The easy way to keep it quiet is with throttle controll, but some hills you do have to open the thing up!

jt · Powermonger!!

Pete wrote:

"When a ktm pilot said his exhaust was under 94db I looked to see what info I could find on noise limits.Seems the ktm in question should be restricted to closed course events."

Just to clarify Peter - I do belive the 'KTM pilot' was talking about his Dads 125 Suzuki 'Road legal MX bike on the thread you refer to

....NOT HIS KTM.........

Just so we don't think that all STD KTM's need to be taken off the lanes

More info Here

And the RTA here if you have problems sleeping...

-- Edited by jt on Monday 28th of June 2010 08:39:47 PM

Pete · Devon's Best

Thanks Jon I've edited my post accordingly after reading the peice again.
I don't see any make of bike as being particularly noisier than the rest,people are apt to take the baffles out of any make to liberate more power,or add freer flowing end cans for the same reason.No one colour or make of bike stands out to me as a wosre affender.

I was once physically attacked by a resident who had heard us riding along an adjoining lane(192-115/4) moments after he had said goodbye to his wife out riding her horse in that direction along 192-240.He was worried for her,whom we did not meet,and by the time we rode past his place after riding the adjoining and following lanes(192-116) he was seriously wound up,enough to swing at me.
I stopped and having remonstrated with him for his violent foul mouthed outburst I reassured the bloke that we had seen his wife approaching the lane we were on some way down a link lane(192-240),that she had waved to me as she stopped her horse to wait for us to pass before continuing.The tec following me confirmed she had been sitting peacefully watching from some way down 240 as he passed from 115 onto 114.
There was a wr400 with us that day whose roar was excessive and it sounded closer and faster than it was.It had a 93db competition end can.I do not think that there would have been a confrontation if the noise had not carried so much further than a standard set up machine does.

Pete · Devon's Best

Does anyone have a db testing app on his phone he wants to test?

Clayton · Clubman A

Some valid points on a very touchy subject, but is an open forum really the place for these matters to be discussed?

gaschef · Devon's Best

Pearcy wrote:

How / where can we test our bikes to find out how loud they are?

My bike barks a bit when it is on full chat as they say, but it has a standard / road legal can.

I know this does NOT mean it is acceptable to people who don't like bikes and want total quiet, and in the nature of not wanting to upset people, I wondered where I could find out how loud my bike is?

The easy way to keep it quiet is with throttle controll, but some hills you do have to open the thing up!

Bring it round Pearcy, I have a decibel meter so I can test it for you. However I will need to find out what parameters are used in testing, such as

A or C weighting scales
What revs to test at or what percentage of full revs is used
What engine loading is used
Is the test conducted stationary or when moving
What ambient environmental conditions are required, temperature humidity etc
What sort of area is used to conduct the test, full acoustic chamber, open area
Plus anything else needed, so if anyone knows please let me know

Torr · Expert

as everyone knows db are measured on a logarithmic scale.. every 10 is a 100 fold increase

I used to have to submit burglar alarm sounders for testing to the BSI, the equipment used seemed very sophisticated and was measured at a specific distance, in a special room, by a man in a white coat!

Audible sound depends not only on its loudness but also on pitch, frequency, air humidity, etc

The nutter with the 32cc garden strimmer with a pitchy little 2 stroke motor sounds a lot noiser and more annoying than my little Honda 4 stroke bike!

I think most councills have a noise meter, and most certainly the ACU race organisers

Harley had an advert "Loud pipes save lives"........................................

but then "You meet the nicest people on a HONDA"

RichT4 · Champion

Loud pipes don't save lives, defensive riding saves lives.

Sound levels are not simple to assess when checking against a set standard as there is more involved than just peak output power so it'd probably be best to avoid getting into that.

FBF · Clubman A

Got to say when I had my Slash pipes on my Virago custom bike no-one walked out in front of me down town, whereas my Kawasaki ZX9R was quiet until you open it up and had many a person fail to see and hear me coming whilst pootling around town.

For Trail riding the quieter the better though. I fitted the DEP power bomb and exhaust back onto the KTM, it seemed too loud to me so changed it back to standard.

One should note that many standard and replacement silencers have packing in which has to be replaced every now and then. Lack of back pressure saps power from 4 and 2 strokes alike.

RichT4 · Champion

FBF wrote:

Lack of back pressure saps power from 4 and 2 strokes alike.

Actually back pressure is a negative side effect of creating increased gas flow velocity. Back pressure itself is best avoided on 4 strokes.

Now I though packing the baffles increased air flow by filling the cavity in the baffle which would resonate without packing. It would also generate vortexs that cause drag on the escaping gases hence increasing the 'back pressure'.

There is so much to exhaust design and don't pretent to fully understand it but I have gained an appreciation of it.

PS F1 cars have about the most advanced engine design going and they do not have baffles, or any intentional back pressure. biggrin

Ming · Devon's Best

RichT4 wrote:

PS F1 cars have about the most advanced engine design going and they do not have baffles, or any intentional back pressure.

And are so whisper-quiet that the noise is added on by the TV companies to make them sound fast...... confuse

doh ! · Clubman A

new limits may be coming in for events next year could be 118DBA at full revs at 2mt distance think this is what enduros and mx are looking at the french used this technique of testing at le touchet this year not sure about road use but if its stamped and original or enduro 94DB cant see a problem with using them listen to all the boy racers in their corsas novas etc out on the highway

RichT4 · Champion

Ming wrote:
And are so whisper-quiet that the noise is added on by the TV companies to make them sound fast......

Yeh, but the point being they don't feel that back pressure will increase their engines performance. aww

devondan · Champion

Torr wrote:

as everyone knows db are measured on a logarithmic scale.. every 10 is a 100 fold increase

Noit isn't a 100 fold increase !!!!!!!! A 10 Db(A) increase is generally percieved as a doubling of sound level. As I recall if you increase vehicular traffic by 100 times then you get a percieved doubling of noise, hence the confusion I expect.

Measuring noise is a complex matter, but in respect of Db(A) a 3Db(A) increase is considered to be the point at which you can hear a difference. This is a good read.

Dan

-- Edited by devondan on Tuesday 29th of June 2010 06:20:39 PM

jt · Powermonger!!

RichT4 wrote:

FBF wrote:

Lack of back pressure saps power from 4 and 2 strokes alike.

Actually back pressure is a negative side effect of creating increased gas flow velocity. Back pressure itself is best avoided on 4 strokes.

Rich - I have a supertrapp on the HD with removable plates to allow adjustment of the backpressure and I can tell you with absolute certainty that the difference of reducing the back pressure if in fact very large....reducing back pressure means the bike will 'rev out' but means a quite large reduction in bottom end torque - In fact so much of a difference that generally if I am going to carry a pillion any distance I will up the back pressure (reduce plates) as for 'load hauling' it's much better - if I'm going solo and want to 'crack on' I will add plates and reduce the back pressure and then the bike will 'pick up' and rev out far better.....

If you want to try come round and have a play - I promise you will notice the difference....I would disagree that its to be avoided and would argue that in fact it it the opposite.... hmm

The other big thing I have noticed over the years of HD owner ship is the big difference that the link pipe makes.....

jt · Powermonger!!

Clayton wrote:

Some valid points on a very touchy subject, but is an open forum really the place for these matters to be discussed?

I dunno mate - i think we are showing that we do care, are concerned, and are keen (enough to even try our own DB tests !) to ensure our bikes a as quiet as possible...

Well my view anyway hmm

Pete · Devon's Best

No reason why this should be a taboo subject.
Lots of very good info in the resulting posts,esp the RTA link.
Better to be well informed in order to counter the often bigoted anti's.

RichT4 · Champion

I know what your saying JT .. wink

My KLX had a removable plate on the exhaust which worked in the same way, I left it on most of the time as I preferred the feel of it with the low end grunt.
What I didn't appreciate at the time is that by removing the plate I was also leaning out the mixture and should really have re-jetted because of it.
Maybe if I had I would have got my low end grunt back?

Exhaust design & back pressure is a much argued about subject. There are a lot of effects taking place and it's so much more than just simplistic gas flow.

But I can't argue with you. I have felt the effect of fixing the restrictor plate on my KLX and felt the better low end.
I have also tried the make the same thing for my DRZ and did not get the same results. The restrictor plate just lowered the performance across the whole rev range - hence my saying that exhaust retrictors do not make power. confuse

devondan · Champion

I agree rich, What ever the science about pulses and scavenging, as we all should know its not just about max HP its where it is delivered and over what rev range that is important. I made a straight through pipe for my old Ford consul once, it sounded great but I couldnt get it off the drive!! after I stuck a mini back box on the end it worked a treat.

Loud is often not faster although it might sound it!

Anyway the re-made 90 degree elbow at the end of the GG silencer has quietened it nicely and stoped it melting the number plate as an added benefit! GG now has its MOT so only the Bandit and YZ to go!

Dan

FBF · Clubman A

Scavenging effect of the exhaust makes a great deal of difference to performance, with a single cylinder though you don't get so much effect as a multi cylinder. Back pressure has a part to play but for ultimate power you have staright through pipes like on a dragster, it all depends on what you are trying to acheive.

You can alter and play around with settings and baffles to tweak bottom end power and top end etc, but in reality we don't really need a massive amount of power for the lanes. I would be happy with a 15bhp as long as I had plenty of bottom end torque, how about a diesel? biggrin

I'd be happy to ride an electric bike, plenty of torque from low down, whisper quiet and environment friendly, its just the length of the cable I find prohibitive.

RichT4 · Champion

I'm watching electric bikes with keen interest. Once the price comes down & the range increases I'll consider one.

I'd also like a diesel bike

-- Edited by RichT4 on Tuesday 29th of June 2010 10:28:31 PM

Clayton · Clubman A

Pete wrote:

No reason why this should be a taboo subject.
Lots of very good info in the resulting posts,esp the RTA link.
Better to be well informed in order to counter the often bigoted anti's.

I have absolutely no problem with the subject matter, and totally agree that being well informed is vital for all TRF members, but the key to winning any argument is to know as much about what you are trying to defeat as possible, and I just feel with all this "very good information from the resulting posts", we're scoring a bit of an own goal by supplying it to those who can and will use it against us, my point is there should be a place on here were this can only be viewed by members, and then constructive discussions on sensitive matters can continue.

jt · Powermonger!!

RichT4 wrote:

I'd also like a diesel bike

Come ride the HD then Rich - very similar disbelief

and see how you like it biggrin

Won't go off topic so will start a new thread - have a look at the link on the new diesel bike thread rich..... wink

-- Edited by jt on Wednesday 30th of June 2010 04:41:45 PM

Torr · Expert

devondan wrote:

Torr wrote:

as everyone knows db are measured on a logarithmic scale.. every 10 is a 100 fold increase

Noit isn't a 100 fold increase !!!!!!!! A 10 Db(A) increase is generally percieved as a doubling of sound level. As I recall if you increase vehicular traffic by 100 times then you get a percieved doubling of noise, hence the confusion I expect.

Measuring noise is a complex matter, but in respect of Db(A) a 3Db(A) increase is considered to be the point at which you can hear a difference. This is a good read.

Dan

-- Edited by devondan on Tuesday 29th of June 2010 06:20:39 PM

That is decibel number..... general problem with general publics lack of understanding of mathematical notations!

90 Db is loud ... 100 is deafening

Quiet pipes attract less interest!