[Technique] Réalisations de Maarten JANSSENS

get a more laminar flow --> less sudden "bang" with atmospheric air?? It does look nice   

That thing aside, I think on the sketch option A is the best, Option B will give more backpressure at a smaller rpm-window?!

I saw an aftermarket full exhaust on a 1199. Can't remember exactly, but was probably a Leovince system. I also saw this on the SBK factory version (Termi ?) The primary tube (from head to junction) is very-very-very big, about 70mm. With Inline-4 rules in mind, bikes or cars, you would say it is way too large.
Then both cylinders tubes joins in X section and goes in a 1-2 to each silencers, with tubes of about 45-48mm, which in turn seems very small. This what we roughtly measured.

On Aprilias V2 (1000cc), the best Akra full exhaust is the EVO6. The primary tube are 45mm for about 15-20cm, then expand to 65mm for about 40cm up to the joining X. After the X, tubes are going from 45mm to 65mm on all the length of about 50cm. Then silencers are conical, with 65mm entry and 52mm outlets.  

We all know these primary tubes are way too big to allow back pressures to help scavenge cylinders. But my feeling is "RPM raise" (accel) is too fast to have full benefits of "standard" diameters and length. So having big tubes acts like resonnant chambers, allowing minimum "resistance" in cylinder emptying phase. Then the small tubes act like venturi with quasi-constant speed/pressure pulse to help lower dB.

Angelo

When Ducati designed the 999 the pass over some rules of usual technicla designs and "create" an exhaust with this big diameter and small length on one cylinder, and a more conventionnal one on the other cylinder. The goal was to have the same resonance characteristics with different forms allowing a more free design of the whole bike.


--
Stéphane

Polux rsv a écrit:

I saw an aftermarket full exhaust on a 1199. Can't remember exactly, but was probably a Leovince system. I also saw this on the SBK factory version (Termi ?) The primary tube (from head to junction) is very-very-very big, about 70mm. With Inline-4 rules in mind, bikes or cars, you would say it is way too large.
Then both cylinders tubes joins in X section and goes in a 1-2 to each silencers, with tubes of about 45-48mm, which in turn seems very small. This what we roughtly measured.

On Aprilias V2 (1000cc), the best Akra full exhaust is the EVO6. The primary tube are 45mm for about 15-20cm, then expand to 65mm for about 40cm up to the joining X. After the X, tubes are going from 45mm to 65mm on all the length of about 50cm. Then silencers are conical, with 65mm entry and 52mm outlets.  

We all know these primary tubes are way too big to allow back pressures to help scavenge cylinders. But my feeling is "RPM raise" (accel) is too fast to have full benefits of "standard" diameters and length. So having big tubes acts like resonnant chambers, allowing minimum "resistance" in cylinder emptying phase. Then the small tubes act like venturi with quasi-constant speed/pressure pulse to help lower dB.

Angelo

Do you know why they would make the silencers conical from large --> small?

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ttroncs a écrit:

Design artifice to affirm the technical/male aesthetic of the muffler exits ?
Stéphane

C'est un peu ça que j'avais pensé  

MJ-Works a écrit:

Do you know why they would make the silencers conical from large --> small?

It's quieter !

Not that he's necessarily as great a technical guru as he says, but Neil Spalding talks about exhaust/silencer issues for Ducatis, and in particular the supermono, on the Sigma site.

The Termignoni pipe delivered on the bike had much better top-end than they could get from an Akra (still called Skorpion back then), but the Termi was too loud to pass a Euro noise test. So they compromised by building a tapered core into the larger Akra casing, which gave almost as much top end as the Termi, but was quiet enough to pass the sound meter. I believe it's a trick already used on many of the older Ducati SStk race pipes.

To be clear, it wan't the peak power that was the issue, it was the ability of the bike to continue to make good power beyond the peak: backpressure  from a smaller diameter silencer caused the power to drop off brutally just after peak.

ttroncs a écrit:

When Ducati designed the 999 the pass over some rules of usual technicla designs and "create" an exhaust with this big diameter and small length on one cylinder, and a more conventionnal one on the other cylinder. The goal was to have the same resonance characteristics with different forms allowing a more free design of the whole bike.

Although only on the base model! All the performance up-grades were back to a 2-1-2 design. Lots of interesting dyno charts here

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(go up to "reports" to see more)

MJ-Works a écrit:

Do you know why they would make the silencers conical from large --> small?

yes, for noise reduction.

For V2 from 99 to 2003, Akra also produced a single silencer for the standard 2-1 headers. The headers are 42mm, then joining in 65mm. The akra has a link pipe 60mm, and a conical muffler of 60 to 48 (If I am not wrong). This design give the best result on this bike. Lot of other designs are 65 to 50mm link pipe, with 50mm silencers. This give a big dip in power curve at 7500-8000rpm, with small gain at top.
Aprilia was also selling its own race "silencer", probably made by Akra. The link pipe is 65mm, and the internal is cylindrical at 60mm, with a very short cone at the outlet, for noise reduction too. This also give good results.

Angelo

after reading your reply's (thank you polux and graham):

I may say that making a cone from big --> small diameter inside the silencer (almost) doesn't cost power but it does bring the noise down?!

Then I'd have to go for this new "option D" ? :

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more (spread out) power because of the cone going from small --> big in the first silencer and the lager diameter tube after that first silencer

The noise kept "in the limits" because of the cone in the second silencer going from big --> small... RIGHT?

Silencer length seems to have a role.  On EVO6, silencers are short. All other headers use long silencers. The KTM 450 for Dakar race use two long akra silencers.

My option E, without any calculations   :
-From head flange, about 15-20cm of same head diameter.
-Then 10cm cone to 65mm diam, even 70mm.
-Input to optional 65mm(70) cylindrical silencer.
-Output of cylinder at 65mm(70) downto, let say 55-60mm.
-Input in (long) (conical) silencer with, let say 45 to 50mm output.

I would not make total length as you made, turning in the belly pan. Only a straigth design.

Angelo

Polux rsv a écrit:

Silencer length seems to have a role.  On EVO6, silencers are short. All other headers use long silencers. The KTM 450 for Dakar race use two long akra silencers.

My option E, without any calculations   :
-From head flange, about 15-20cm of same head diameter.
-Then 10cm cone to 65mm diam, even 70mm.
-Input to optional 65mm(70) cylindrical silencer.
-Output of cylinder at 65mm(70) downto, let say 55-60mm.
-Input in (long) (conical) silencer with, let say 45 to 50mm output.

I would not make total length as you made, turning in the belly pan. Only a straigth design.

Angelo

OK...a few questions   

- why would you use a cylindrical first silencer?
- why would you make the pipe between the two silencers go from big --> small?
- Why would you use a long second silencer?
- What would you do if you had to use my system until the first silencer?

Basically, you would do everything the opposite of what I would do, right?    If I hadn't tested first with different lengths then I'd be getting worried now.

kind regards,

Maarten

MJ-Works a écrit:

- why would you use a cylindrical first silencer?

To replace it with a single tube, depending on the result with the last silencer.

MJ-Works a écrit:

- why would you make the pipe between the two silencers go from big --> small?

After gases pulses had expanded in the first big tube, the flow will be mor continous in the smaller one.

MJ-Works a écrit:

- Why would you use a long second silencer?

More absorbtion volume, helps to lower noise. A single akra full titanium silencer is about 1.6kg.

MJ-Works a écrit:

- What would you do if you had to use my system until the first silencer?

Not sure to understand the question.

MJ-Works a écrit:

Basically, you would do everything the opposite of what I would do, right? If I hadn't tested first with different lengths then I'd be getting worried now.

Which kind of total length did you tested ??

Angelo

Angelo, je crois que Maarten voulait demander: si tu possédais déjà une très belle ligne titane comme la sienne, jusqu'au début du premier pot, et tu ne voulais pas la mettre à la poubelle, tu essaierais quoi pour la partie en aval ?

Et puis moi, j'aimerais profiter de tes connaissances pour demander : a-t-on jamais essayé deux lignes indépendantes sur une RSV de course ?

Oui, on a essayé sur un proto à moteur RSV. Les deux tubes étaient séparés, en diamètre 50mm, puis silencieux en 60mm. Les arbres à cames étaient calés à 118adm/118ech (origine:108/114). Dans cette configuration, le moteur n'avait pas d'allonge, mais était très coupleux. Un vrai bi-monocylindre   

Angelo

GrahamB a écrit:

Angelo, je crois que Maarten voulait demander: si tu possédais déjà une très belle ligne titane comme la sienne, jusqu'au début du premier pot, et tu ne voulais pas la mettre à la poubelle, tu essaierais quoi pour la partie en aval ?

Et puis moi, j'aimerais profiter de tes connaissances pour demander : a-t-on jamais essayé deux lignes indépendantes sur une RSV de course ?

exact!

polux: I've started out with another system first (the twin megaphone setup that you can see on page 1) but it was too heavy and I didn't like the packaging (not compact enough). I didn't test all that much with that exhaust, only put it on the dyno once and it gave a nice result, very flat torque curve. I hadn't modified a lot on the engine back then apart from flowing the head, so I never used it with the racing camshaft and a shortage of  money + an interested buyer forced me to sell that exhaust.

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Then I started with the single pipe plan that had to have a silencer underneath the engine. I first made a simple steel version that went straight to the silencer, all in 48 mm (size of the exhaust port).
I could only make this with a length of +-80 cm, (that's too long according to my calculations that said it should be +- 68 cm). It gave a very ugly, almost harley-like sound and the engine almost didn't run! When I opened the throttle very fast it would stall with a big bang  

When I fitted a very long silencer on that pipe (just to test it) that problem was better but it still wouldn't rev as fast as it should + the longer silencer didn't fit underneath the engine...

That is when I decided to make a longer pipe to achieve +-2x the calculation length because in theory that would be good too and that is how I ended up with the exhaust I had

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This actually worked pretty good and this is how I raced it on Oss and on the Red Bull Ring. The only problem was that it didn't provide enough ground clearance and the sound was near the maximum (103 dB) That is why I had to adjust it with a second silencer as you can see on page 2 in this topic!

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BUT that clearly took away power and when I removed the second silencer and put that short one underneath the engine it ran GREAT. So that is the history behind the exhaust and the reason why I'm trying to tune it better now without making too much noise.

Ok, I better understand your question.
As a test, you can keep the first section. Then build the same design, but with bigger diameter to allow gasses to expand before reaching the outlet.
On the proto I mentionned before, we also had noise problems, mainly due to a to small silencer. Adding chicanes before/after silencer make small effects on noise, but big effects on power   

One way you could explore: add a catalist (cataliseur) before the final exhaust. Even at outlet. We worked on a Viper for a customer. He races on track in germany DMV championship. Due to regulations, catalist are mandatory. We made tests on the dyno and found that it lower noise whithout loosing power. On this car, which have a V10 motor, each header is going on the side, with a silencer under the doors and the outlet is just in front of rear wheel. The catalist is added after the silencer.
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Angelo

Polux rsv a écrit:

Ok, I better understand your question.
As a test, you can keep the first section. Then build the same design, but with bigger diameter to allow gasses to expand before reaching the outlet.
On the proto I mentionned before, we also had noise problems, mainly due to a to small silencer. Adding chicanes before/after silencer make small effects on noise, but big effects on power   

One way you could explore: add a catalist (cataliseur) before the final exhaust. Even at outlet. We worked on a Viper for a customer. He races on track in germany DMV championship. Due to regulations, catalist are mandatory. We made tests on the dyno and found that it lower noise whithout loosing power. On this car, which have a V10 motor, each header is going on the side, with a silencer under the doors and the outlet is just in front of rear wheel. The catalist is added after the silencer.
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Angelo

I think I'm now going to get the pipe zircotec-coated and make "option D" to make the best of what I've got now.

If I have the money I can make an all new exhaust next winter that incorporates your experience (the Option E with some calculations), is as straight as possible and has bigger diameters and a long silencer next to the wheel etc.

Just curious: Have you ever tested the effect of a silencer on a megaphone that has a "counter-cone" like mike Edwards used on the "Gordon's alive" project?

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thanks for all your help!

Maarten

I have never seen such design. But I remember a similar design for a single RSV silencer. The counter-cone was made inside the silencer, few cm after the entry. Then, another cone, opening up to the outlet, with big diameter. Both cones were inside the silencer, made of perforated and rolled plates.( plaques perforées et roulées)
Superkart could confirm this, he should have pictures of this silencer.

Angelo

Oui , c'est bien ce principe qu'il y avait sur les silencieux ninja de 4t
Je vais te retrouver les photos sur mon PC.

Ça marchait bien. La courbe de puissance et couple étaient plus remplies a mi regime qu'avec des silencieux d'autres marques , mais c'était a peu prêt pareil en puissance maxi.
Par contre  c'était très bruyant.
Ça faisait environ diametre entrée 80, longueur convergent 150 ' diamètre restriction 45 , longueur divergent 300 et diamètre sortie  50-55

Ça change aussi suivant les versions 1 ou 2 silencieux.... sur mon premier rsv il était énorme et ne passait presque jamais au sonomètre.

Est ce que vous avez pensez au valve qu'on trouve en tunning auto,,, c'est commandé par câble  et c'est la bonne solution lorsque le commissaire de piste vous présente le sonomètre

Sans valve a l'echappement, aucune 600 ne passeraient au sonomètre....





Je suis ce post avec attention, continuez!!

Merci Superkart.

Exhaust valve !!!! that's the magic word I forgot. On superbike RSV4 and BMW, the exhaust valve is always opened on track. It is closed only on pit-lane    Try to locate a used 1198 factory exhaust, the valve is big enough and easy to turn with a simple cable.
Years ago I implemented one at the Leovinci silencer outlet. Open/close was activated riding, using a cable and bicycle gear lever, fixed on the left handle bar. Worked perfectly at low throttle openings in village. Then I opened the valve were nobody could hear me. Worked for month before I tried WOT with closed valve to show it to friends. Axle broke and valve was ejected 10 meters away. Standard anchor silencer was back again.

Angelo

A mon avis , il faut faire le pot qui a le meilleur agrement moteur (pas forcement les CV)  et lui colle une valve pour passer au sonometre.
Aucune moto moderne sans Valve a l'echappement ne passe les 102Db  "valve ouverte" .

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la plus grosse version du ninja SBK pour les 1000..
le site ninja n'existe plus , mais on doit pouvoir trouver des courbes pour avoir une idee ( san sles chicane de 30mm en bout !!)

le genre de grille NINJA SBK
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Polux rsv a écrit:

On superbike RSV4 and BMW, the exhaust valve is always opened on track. .... Axle broke and valve was ejected 10 meters away.

Non, non, mais tu n'as pas lu les experts techniques ? C'est pour ajouter du couple qui manque si cruellement aux moteurs de 1000cm3. Le 600, par contre, n'en ont aucunement besoin   

But Maarten, I think if you fit one, you should make the control more discreet than a bicycle gear lever, the sound meter crew may not appreciate it :)

yes, the tecnical control staff have a better visual and hearing acuity than the cop who controlled me   

Angelo

This is the reason I asked about separate pipes: a friend who races (and wins) the NZ F3 championship with a "slightly" modified SV650. He wanted to run separate exhausts so he could build a carbon swingarm: the stock pipe routing would heat the epoxy too much. Unfortunately he couldn't get good power from it

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GrahamB a écrit:

This is the reason I asked about separate pipes: a friend who races (and wins) the NZ F3 championship with a "slightly" modified SV650. He wanted to run separate exhausts so he could build a carbon swingarm: the stock pipe routing would heat the epoxy too much. Unfortunately he couldn't get good power from it

looks like a very fun bike!!

I think that the tubes are the same diameter for too long and that may cause the problem?

This night in bed I decided that I'm going for my option D type for this season  

I'm only doubting about the next thing   :

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"2" is easier to make so I'm leaning towards that option!

the man that made my beautifull 2-stroke exhausts (Fedor Copal) for my 250 RR bike is going to make the internal parts for the silencers.

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He has an awesome  "secret" machine to roll the plates with the right cones and cut them perfectly straight. And he's an affordable and very nice guy. He also made the megaphones for my supermono. credit were is due!