A quiet and powerful exhaust system in the making....update

Hey all,

Sometime back, in this thread, you might recall I was playing around with an exhaust and silencer system with the plan to create one that was both quiet and produced power.

It has been a real challenge, that's for sure!

This afternoon I went down to the dyno to put the best ones to the test to the test.....on my FS650c - 15 in all.

Under noise testing, 6 of my exhaust systems would pass the 2008 FIM enduro noise regulations with flying colours, a couple of which are about 4dbA lower even when tested inside my garage.

2 systems will, with minor adjustments pass the requirements under road regulations and it should therefore be possible for me to get them approved as road legal. Also under testing, the quietest 6 were so quiet that it is the engine noise/intake that becomes the biggest noise problem.

The other systems are slightly louder, going up to a massive gas flow system that only produces 98dbA under the FIM testing procedures.

Many of my prototypes are quieter than the Husaberg OEM enduro silencer throughout the entire rev range, which of course is E marked.

On the dyno, although testing was cut short by what is possibly a stator failure, I got to test three of my systems plus the OEM for proper comparison and only my most restrictive silencer did not match the Husaberg OEM enduro system on power. It was a couple or three horsepower down comparatively.

The others were on par or better by several horsepower.

The most restrictive of my silencers given that it only loses a couple of horsepower compared to OEM should be an ideal candidate for a 450, for example.

After fixing the blips we experienced today, which will hopefully only be the stator, and modifying one of the silencers slightly, I will be back down to the dyno next week to test the rest of the systems and I'll post the results with the dyno charts also.

On a couple of the systems it is looking really positive though and they show a nice linear power curve. One system is nice because it has a soft bottom end that builds gently and instead of the power tailing off where the oem one does, it continues to make better top end power for longer. The feedback I've had from enduro riders is that this is a preferred curve, but we'll see.

All the best,
Simon[/i]

Thank you for your support, DaleEO!

Simon

Jocke_D said:

Go Simon Go !!!!!

I read the last thread a couple of times and was equal impressed both times

Have you thought of making a twin system to possibly improve power as well as getting even lower noise??
If I have a twin exhaust already (RAAS), will you be able to make just a couple of silencers for my existing header pipes??

Is any larger production plans in the pipeline?

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Hey there Jocke,

I think the answers are yes, yes, and possibly yes????

I have made prototypes that are both single and twin systems to see which ones make most sense. Apart from removing the bracket for the plastics on the rear right hand side, the twin system doesn't require any frame or shock modification.

In my experience it has also been interesting to find out that two silencers does not mean less noise, like some might have us believe.

Interestingly if you have one silencer and then just add another with all else being equal you will most likely end up with more noise - by about 3 dba at least - of course you may increase potential mass flow, but it doesn't necessarily end up that way, nor does it necessarily mean more power either. However, if you restrict the exhaust pipe flow area within each of those twin silencers while retaining the full outside diameter of the silencer so that you increase the expansion ratio between the exhaust pipe and outer sleeve, then you might see a reduction in the noise levels. I'll leave it at that

Following the results I had this morning, I need to check and think about how to proceed with things. I'll be adding the results to this thread shortly.

All the best,
Simon

70marlin said:

Simon have you ever had the silencer off an 02 FX470E dyno’d.

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Hey Marlin,

Yes, I have one of those silencers in my garage.

70marlin said:

At sound check when the bike was new it test at like 82 Db’s

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At idle maybe, but not a chance at either a piston speed of 11m/s or 13m/s.

Sorry to be so blunt about it but you'd be hard pushed to even get 82dbA at a meter away from the front of the bike :wink:

Cheers,
Simon

The test result are in.....

Well, I got the bike fixed and there was a slot available down at my dyno Friday morning, so off I trotted blurry eyed first thing.... nervously, to get this round of testing completed and see where we were at...

So before going any further, let's just recap briefly what the purpose of all this stuff has been.

First, a good few years ago I had a virus that attacked certain parts of my brain and caused permanent damage. As a result I haven't been able to work and my capacity to function has seriously been limited ever since. I've also not been able to ride my bike, hence my appearances on the forum are sporadic at best. However, instead of going completely mad doing nothing, I decided to go along and do something completely mad instead, during the periods where I've been up to doing something. That's why it has taken me as long as it has to get this far! :roll:

Anyway, I took a bit of an interest in exhaust system design and first built a race system like pretty much all of the others on the market just to see if I could get something pretty good - I did and it worked.

I then started thinking about the noise issues and thought about whether it would be possible to build a system that not only allowed decent power output, but was quiet, by comparison too. Not too quiet, mind you.

So what do I mean by quiet?

When I was racing in supermoto, we had big exhaust pipes with straight through silencers we're all familiar with that have a perforated tube inside with packing going around them. These pipes are usually considered to give the most amount of power for a single.

The problem with these pipes is that although they were always supposed to be limited to a noise output of 98dbA, in reality we could never even get close to that. I received a drive-by noise measurement from a Yamaha 450 with a motorcross silencer which was in the order of 130dbA.

The other problem is that in order to even get close to the 98dbA limit, the exit of the silencer had to be reduced slightly and they have to be repacked with new packing on a very regular basis. At a motorcross meeting the bikes might pass a noise test on the Friday but by Sunday, the packing would have deteriorated so much a bike would be unlikely to pass the test again. The other thing is that as the packing deteriorates there is also a tendency towards a reduction in engine performance too.

First off I wanted to make something that didn't have any packing in it and therefore it would be maintenance free and a consistent noise output at only 98dbA without excessive power loss.

It then became clear that noise was becoming more and more of a problem for all of us, even at enduro events, so I re-drew my parameters to aim for achieving several levels of noise performance: 1)90dbA, 2)94dbA and 3) a loud system for road race circuits of 98dbA. There was also a 4th half aim just to see how quiet I could go.

I also decided that not only did I want to achieve this according to FIM tech regs at 11m/s piston speed it would also be relevant at 13m/s because noise regs were about to tighten even further as are the limitations we all face when wanting to go out and ride.

Initially my performance benchmark was with the full blown race systems like the Akropovic, FP and Doma exhaust all of which I have extensively tested. However, given that even these at quiet venues require a baffled insert to make them quiet enough, they will naturally lose their power output. I noticed that a lot of race silencers, even at road race events need baffles in them to pass noise testing and those baffles eat power.

So, my benchmark changed to using the stock OEM enduro silencer and system - it made more sense that way. Even the OEM enduro silencer (without the spark arrestor fitted to the exit) is a bit touch and go when it comes to noise testing at 11m/s piston speed and tends to need fresh re-packing. In my tests the enduro silencer I have would not pass the 94dbA test at 13m/s.

Power output with the stock silencer, however, is pretty good. With a supemoto race slick I have consistently measured an output of 56 horsepower at the rear wheel but in using something like an Avon Distanza this reduced to about the 53 hp mark, which is fine.

So basically the aim right now is to achieve more power output and less noise output than the standard OEM enduro silencer - given that this is what most people will be upgrading from. With refinements I anticipate that I will be successfully able to take on the full blown big flow mufflers in due course - I'm nearly there right now, I've just got to find about 1-2 more horsepower at the top end of the rev range.

The systems I've made consist of two types, one is a single tail pipe going into a single silencer, just like the standard system, the other is a twin silencer system that a two-into-one-into-two system. The twin silencer exhaust doesn't require any modifications to the bike other than to remove the metal bracket on the right hand side of the bike at the rear.

All in all, I had 15 different combinations to test and here are the dyno runs for single and twin tests that are for now relevant. The OEM run is in bold in the pictures and the t after the silencer number denotes a twin and s a single:

#1s - very quiet not great power unless you're trail riding


#1t - very quiet and pretty good power


#2s


#2t


#2t and #3t


98dbA silencers - #4s and #5s



As you will notice, two of the twin silencer systems , #2 and #3 produce significantly better power across the entire rev range than oem. Both of these produce significantly less noise, one of them half the sound energy, the other less than half and both of them would easily pass FIM enduro noise tests.

As a result of the tests, for now I have chosen two silencer designs with two single exhaust systems and two twin exhaust systems to take further which I will build so that they can be real world tested on a couple of bikes in extreme conditions, both in supermoto and in enduro environments. One of the systems, the one which doesn't produce much power on the 650 looks like it might be ideal for the 450, however. These are #1s and t and #2 s and t

Overall, each of the options I have chosen to take forwards are below 94dbA at a piston speed of 13m/s, and one is below 90dbA. In actually fact with minor adjustments, one currently looks like it would pass the British Standard test for road legal replacement exhaust systems (82dbA under acceleration load).

I know this is all a bit of an anorac kind of thing, but I hope it is of interest to people other than just me. I'm certainly enjoying the challenge.

All the best,
Simon

PS, eventually, I will look at a US Fire Service approved spark arrester, but that is to come.[/img]

70marlin said:

No problem. It was just from memory. All I remember was it was very quite. Have you any test data from the silencer, dbA and performance? I still can't out ride this pipe with my skill level.

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Now you're asking :wink: I definitely have some copy dyno charts knocking from about six years ago, they're in a manual file somewhere. It may be after the xmas that I get to dig them out, but I'll let you know how I get on.

Cheers,
Simon