I have been told by someone that by restricting the exhaust system to control the noise output on a bike will in turn overheat the motor and destroy it.. Yes/no??

I have also been told by someone else that by creating more heat will help with the combustion of the air/fuel and in turn create more power..

I realise it's probably a fine line between the two.. Restrict it to much and you'll lose power.. But if it's restricted just enough to get under a certain noise limit then, then it's not being restricted *** all, I'm only talking about knocking 5-8 db's out of the bike..

Induction noise would also be a contributing factor to the noise output so a makeshift airbox should help.. Bikes allready run foam filters alone..

What about heat wrap.. Is it a bad idea to wrap a 2T exhaust in heat wrap??
As there'd be a certain portion of the noise coming from the expansion chamber's..

The type of bikes I am talking about are Moriwaki 80's, Metrakit 80's and the like, jnr road race bikes or Bucket bikes to us old folks..

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MC18 Race bike project..
MC21 Race bike..

Are you planing on road registering your moriwaki?

That would be cool as!!!

Andy

Bandit7

This is not NSR specific, and should be in Open Discussion in the Members Area.
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OOPS..

Sorry about that Andy.. I did not realise..

The Moriwaki can never be road rego'd Bandit (Andy)..



So to make this thread about NSR's.. Does the same senario apply to NSR's as I may also(depends on db readings) have may have do something similar to get the NSR's on track at Lakeside.. I just thought I'd ask here seeing as though all the bike's mentioned share the same thing in common and that being the powerplant..

*Lakeside is a racetrack that has noise restrictions imposed on it..*
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MC18 Race bike project..
MC21 Race bike..

Glen wrote:I'm only talking about knocking 5-8 db's out of the bike..

A drop of 3dB is a halving of the sound level, so you're trying to make your bike 4 times quieter? Might need a trailer for the silencer...
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How is a drop of 3db's halving the sound level??

Say for instance my bike reads 100 db's at 5metres, whilst passing the sound meter under full throttle.. Now if I wanted to knock 5db's off, then I'd be aiming at a 95db reading.. How have I now reduced my bikes sound output by more than half??
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MC18 Race bike project..
MC21 Race bike..

Because levels of sound intensity vary hugely, a linear scale for measuring the magnitude of a sound source wouldn't work so well. The Decibel scale is logarithmic, not linear.

As this graph shows, if you increase by 3 decibels, you have doubled the power.
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FJ1100 Sporting relic
GTS1000 oddball

Logarithmic scales.
How i hated you at high school

Redusing induction noise alone will knock off a couple decibels. Get your self a factory airbox with lid, and drill some holes in it. This will be heaps quieter than open carbs.
The factory pipes are double skinned, and while being heavy, are pretty quiet in terms of resonance produced.

Mufflers will be your only gripe.
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Not convinced that the graph posted above is any representation of actual testing I have performed trackside..

Personally speaking myself and my wife run racing and track day events at Lakeside.. Included is Minimoto, Minitard, Scooters, Postie Bikes, Buckets (Moriwaki's and the like) and Supermoto..
All the 2T bikes except the Scooters have had to modify their pipes and or airbox's to reduce the db output..

This next picture is a simple slip-on muffler that was made up for the sole purpose of reducing the db output.. This slip-on knocks anywhere between 5-8db's of the overall reading, certainly does not require a trailer to carry it around and most definately does not reduce the power by over a half..



This is a Minimoto one but I also run the exact same design on my Moriwaki, only difference is that the Mori one is wider in diametre..
There is a ball of coarse steel wool placed inside the slip-on which gets pressed upto the end of the original muffler..
Now from personal experience running all my bikes with and without the slip-on, there would only be a 1hp drop at maximum, this test has also been performed side by side with other bikes to guage if one out performed the other, which it didn't..



So back to my original post..

1. I have been told by someone that by restricting the exhaust system to control the noise output on a bike will in turn overheat the motor and destroy it.. Yes/no?? EDIT: Also from riding and testing I have not noticed any increase in temp on my gauge whilst riding.. I only ask this becuase some apparent guru says otherwise..

2.I have also been told by someone else that by creating more heat will help with the combustion of the air/fuel and in turn create more power.. Yes/no??

3.What about heat wrap.. Is it a bad idea to wrap a 2T exhaust in heat wrap??

4.Is it a really bad idea to run one of the custom slip-on's on an NSR??

All question's are in regard to NSR's..


Oh and 80XAR, I've got stock airbox's although I'm currently not running them on the NSR's and although I have stock pipes I'm getting TYGA pipes in the next few weeks..
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MC18 Race bike project..
MC21 Race bike..

With regard to your 2nd question, if there is too much heat in the cylinder wouldn't this increase the chance of detonation? Sounds bad to me.


edit: Glen you may have misunderstood the power ratio, this isn't meaning the power output of your engine.

Then can't the jetting just be changed to suit??

I must have misunderstood.. What exactly does the 'power' part of the graph refer too??

I take it some may have heard about Nology leads and silver spark plugs.. Would folks also say that these would be bad news for the motor as they create more spark and in turn more heat?? But would it not come back to jetting to suit??
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Paranoia about failure will ensure nothing but failure to ever reach potential.



MC18 Race bike project..
MC21 Race bike..

Glen wrote:Not convinced that the graph posted above is any representation of actual testing I have performed trackside..

What?
A 3db increase represents a doubling of sound pressure, that's a straight fact.
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Glen wrote:Then can't the jetting just be changed to suit??

I must have misunderstood.. What exactly does the 'power' part of the graph refer too??

I take it some may have heard about Nology leads and silver spark plugs.. Would folks also say that these would be bad news for the motor as they create more spark and in turn more heat?? But would it not come back to jetting to suit??

I think the main factor that affects cylinder temperatures IS the jetting, and as you will know, lean = hot, rich = cool as the excess fuel helps to remove heat from the combustion chamber. You can run different heat range plugs, but I don't think this makes the engine run any hotter or cooler, it just dictates the operating temperature of the plug itself. Too cold and it won't get to it's self cleaning temperature, too hot and it will melt and possibly cause pre-ignition.

Sound is pressure waves travelling through air, a mechanical vibration, and there is energy associated with it (Joules, J), and hence power (Joules/Second, W). So that's what the power part is referring to. A -3 dB drop in sound level corresponds to a halving of the intensity of the source.

I would have thought that a stronger spark could only be good, faster burn > bigger bang > more power!

Hopefully I have my facts straight here.

Glen, they're talking sound pressure, not engine output.