Ooops - not meaning to be negative - Sorry!

Personally I think it's great that MTC have taken the time and trouble to invest in making such a vast array of exhasut options for our beloved Ten'.

From memory the std set up is really heavy, which is why I removed mine and the also overly heavy rear light effort.

Perhaps MTC can add some science here, but I just do not see the need for two pipes other than aesthetic. Yes, the lovely MTC cans are lighter and that is of course good compared to standard.

I tend to change exhausts as a 'must do' on just about every bike I've owned since 1982... and that's a lot of bikes.

I prefer the single can solution from both aesthetic and weight view points and also prefer the RG tail tidy which weighs about a gramme (when compared to standard set up).

Once again - great to see the choice and I hope MTC are able to offer the single can solution too in the future so that all options are covered and keep up the good work.

Cheers.

I don't think you are being negative, I agree with you. The bike comes with a single can system (albeit with two vents) and it is heavy.

I too would like to know the benefits of a dual can system on a bike over a single can system.

I appriciate the difficulties in producing a single can for the Tenere (in that it's a fairly short can)

I would like to see something of the science and engineering that suports the use of two cans over one.

A single can system would certainly be on my shopping list, as long as it was value for money.

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Thanks GULG.

Due to me losing all my Ten' pic's when the PC died, I can't recall the exact weights of the original and the single can and I can't be arsed to take it off to weigh it now!

Like you, I'm interested to hear an expert's opinion about gas flow 'n all that. I also fitted Kev's fuel mod and the K&N air filter so other than a PC now, I just have the baffle to take out. Silencing with the standard baffle is more than adequate.

I can recommend the following books if you are interested in learning about exhaust design:
The Scientific Design of Exhaust and Intake Systems (Engineering and Performance)
Four-stroke Performance Tuning Second Edition

Silencing a big single isn't an easy task; the noise frequency is low but penetrating. As the pressure wave moves along the inside of the silencer there are a few different methods of actually providing a reduction in noise. The most common is to have a series of perforated tubes and plates to break up the path of the pressure wave, thus reducing the volume that comes out of the silencer. This is known as a reflective silencer. If you cut open one of these silencers then they will look something like this-



That's a car silencer, but you can clearly see the tubes, plates and volume of space available for the pressure waves to move around in.

What is often referred to as a 'race' or 'straight through' silencer uses the method of absorption through a single perforated tube, wrapped with an absorbing material such as glass mat or wire wool. Like this-



They are referred to as 'straight through' as obviously the pressure wave can pass straight through the silencer, without losing as much gas speed as in the normal reflective type of silencer, thus you lose less power.
They are also very easy to make as all they are is a tube, with a perforated tube inside. You can alter the length to provide more or less silencing, and with an increase in length you will get a slight increase in back pressure.
What is more important in exhaust design is the length, bore and shape of the pipe work from the exhaust port to the silencer. The silencer is only really there to silence the machine. The changes you can make to back pressure via how much you choose to baffle or slow down the gas/pressure wave will have an effect upon the performance of the machine, as will how open or short you have the silencer, or whether you fit one at all.
You can make adjustments as well by the inclusion of cones in the exhaust system, in order to reflect the pressure waves back, or allow them to expand.

However; it is very important not to view changes in isolation, if you are wanting to have a less-restrictive silencer with a view to gaining an increase in power from your machine, then you have to anticipate that the gas speed will increase, and thus your combustion chamber will be emptied faster. Without increasing the amount of fuel, and the corresponding amount of air, entering the combustion chamber, you will have a lean mixture which will provide negative results not only in power, but also in engine longevity.
The XT660 engine has a twin port head and as such the gas speed will be higher compared to if the same engine had a single port head. This in turn means that the amount of silencing needed is greater in comparison to a single port as the frequency of the sound waves will be higher.

After experimentation with single and twin silencers of differing lengths, I believe the most efficient and balanced method of silencing the XT660, with positive results in the power stakes is a longer single silencer with an absorption baffle, placed after a shallow reverse cone megaphone.

Hope that is of some use to you?

Thanks Tom,

Very informative.

I'm going to have a guess that the OE can is Reflective, where the MTC (and any other twin pipe setup) is striaght through, hence an inprovement in performence.

But what of a dual verses single can? both would be straight but I imaging there is some loss of performance (by way of gas speed/pressure or silencing ability) by spliting the pipe into two cans...

I'm trying to understand why a dual can setup is the most popular (for the manufactures), over a single can which should be cheaper.

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Ok to answer your points in order-

Yes the OE silencer is reflective, and contains the catalytic convertor before the baffling. By doing this, the amount of baffling needed can be reduced, but it isn't a very efficient system for performance.

Which brings us on to the next point; I believe that the majority of aftermarket silencers for the Tenere are designed as twin units to fit in aesthetically with the bike once the neat OE unit is removed. As far as weight, and the removal of it goes, you aren't helping yourself by fitting twin silencers, when one would suffice. However; fitting a single silencer to the Tenere throws up both aesthetic and flow problems of it's own.

If you want the most efficient flow you have the silencer on the left of the bike, but this leaves the right hand side of the bike looking very exposed and unfinished. As the bike leans to the left on the sidestand you get to see the dirty side of the silencer whilst the bike is at rest.
If you decide to fit a single silencer on the right hand side of the bike, then you have to add a couple of bends into the system at the point where the gas speed it at it's slowest, so you risk adding more back pressure to the system. This is also true of systems like the Leo Vince link pipe where there is a smaller diameter secondary pipe going to the RHS silencer. The way this secondary pipe is sprued off from the primary will have an effect on the turbulence of the gas flow at that point, again affecting back pressure. I can only speak of the LV system as I haven't had a look around the others available.
I wasn't too enamoured with the LV system and thought it heavy and certainly the RHS silencer is only there for aesthetic balance.

The OE silencer isn't a dual silencer, but a single silencer with twin outlets. By designing it as such the manufacturer can make use of the space efficiently and stylistically it would tick boxes with their design department.

I think the two cans allow gas flow to be less hindered whilst still providing for a reasonable level of silencing otherwise you end up with the dustbin size silencer thats fitted to the XT1200z. Or its all just styling/asthetics.

I still fancy the idea of making an underseat silencer something like the original SXV/RXVs had. Getting it to actually silence effectively might be a bit hit and miss though

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XT660Z - Commuter, Adventurer...Racer?

www.dashmoto.net

Other bikes >> MT-03 / CG125BR-J / ER-6F
Departed >> ZXR400L3 / EC300 / DR-Z400E / DR800S / GPZ500S / GS400

Tom

Firstly - Thank You for a superb and detailed reply, much appreciated!

So, you've added some science to what I kind of figured. For me, weight, performance, sound are the important ones as are aesthetics and I opted for the X Racing single pipe, as it's light ally and the baffle makes it tuneable if I so wish regards to noise only. Clearly this is the perforated tube and the link pipe is really quite straight and as such fast flowing with less back pressure. So with this is mind I need more fuel and air, so fitted Kev's fuel mod and the K&N air filter. I have the ARD cases rack +/- panniers depending on what I'm doing, so to 'balance' the rear end aesthetics (I have the R&G taoil tidy there too) is not on my list at all.. I appreciate however other folk may feel differently.

My Ten' is as crisp as it can be (in my opinion and without altering the engine internals) and certainly is a zillion times better than the standard set up. No jittering, lag and quick on and off the throttle response. Not quite like my WR 45O with FMF, but not bad.

There will always be the need for choice, as consumers are fickle and if there's a good single can option from the same twin can supplier, then I think that manufacturer covers all possibilities and maximises their sales potential. Makes good business sense to me and I hope that choice is available soon, as it will probably be much easier than all the bank transfers etc I had to do for my X Racing pipe - worth it though!

Cheers..

I've moved parts of the MTC thread to here, mainly because it's an interesting thread but not really specific to the MTC ordering proccess.

Carry on....

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