[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked)

Frits Overmars a écrit:

@Jarno: there is no such animal as a flamish language. It is just a pathetic attempt of people living in Flanders (the northern part of Belgium) to speak dutch

Frits, tu as raison, le Flamand est un dialecte issu du Néerlandais parlé au sud du Rhin, et c'est à tort qu'on utilise parfois ce mot comme synonyme de "néerlandais".

Mais il y a des membres Belges très sympathiques sur ce forum, donc s'il te plait n'allume pas un incendie entre Wallons et Flamands sur pitlane !!!

Et puis un Allemand pourrait te dire que le néerlandais n'est lui-même qu'un pathétique effort des Hollandais pour parler allemand avec l'accent espagnol

Jarno a écrit:

Et puis un Allemand pourrait te dire que le néerlandais n'est lui-même qu'un pathétique effort des Hollandais pour parler allemand avec l'accent espagnol

That's right, Jarno. People from every other nation risk to damage their larynx when trying to pronounce the dutch 'g'. Only the Spanish have no problem with it

Ggggggggggggggggggggg-ronie-ggggggen

[quote="Jarno"]

Frits Overmars a écrit:

le néerlandais n'est lui-même qu'un pathétique effort des Hollandais pour parler allemand avec l'accent espagnol

j'adore ta culture


les flamands et l'Espagne.....(les flamencos)

Citation :

Charles V devient souverain des Pays-Bas en 1515. Il devient roi d'Espagne..sous le nom de Charles Ier l'année suivante, à la mort de son grand-père Ferdinand le Catholique. Il s'installe avec un grand nombre de nobles hollandais en Espagne en 1517. Son autre grand-père, l'empereur du Saint-Empire Maximilien, meurt en janvier 1519.

le reste de l'histoire est due à Napoléon ....

[quote="Pickup"]

Jarno a écrit:

Frits Overmars a écrit:

le néerlandais n'est lui-même qu'un pathétique effort des Hollandais pour parler allemand avec l'accent espagnol

j'adore ta culture


les flamands et l'Espagne.....(les flamencos)

Citation :

Charles V devient souverain des Pays-Bas en 1515. Il devient roi d'Espagne..sous le nom de Charles Ier l'année suivante, à la mort de son grand-père Ferdinand le Catholique. Il s'installe avec un grand nombre de nobles hollandais en Espagne en 1517. Son autre grand-père, l'empereur du Saint-Empire Maximilien, meurt en janvier 1519.

le reste de l'histoire est due à Napoléon ....

Merci.
Le pire ce n'est pas Charles, c'est Philippe II, né et élevé en Espagne, et qui devient roi des Pays Bas à la mort de son père.
C'est sans doute lui qui a introduit cette prononciation étrange des "g", qui vient de la "jota" espagnole.
Mais il a aussi gouverné sans grand discernement, et même persécuté les protestants, ce qui a précipité sa perte.

Bon OK on arrête la digression historique.

Et merci à Frits pour son humour

ouppppsss un énorme désoler d'avoir été vraiment trop curieux ça m'apprendra à vouloir toujours trop en savoir :| à partir de maintenant promis je ferme ma bouche et j'écoute avec la plus grande attention

veuillez encore une fois m'excusez de mon action et de ma grande curiosité


amicalement pierre

Questions pour Mr Jan Thiel via Jarno (quand il y en aura assez, peut-être):
- Mr Jan Thiel est-il encore impliqué dans le développement du RSA mené par le team AJO pour la moto de Marquez?

Tiens, j'en ai une autre...

On a vu, sur le graphique aimablement mis à disposition par Frits Obermars, que finalement les puissances maximum des RSA et RSW étaient assez proches.

Sur quoi bute-t-on actuellement pour continuer à faire progresser la puissance par une élévation du régime?

Résistance des matériaux? Vitesse du piston? Vitesse des gaz? Perte de mélange gazeux frais à l'échappement? etc.

vitesse des gaz limité aux subsonique en admission il me semble :idea:

Like Toopack says: the gas velocity is subsonic. Not only in the intake, but everywhere in the engine. Only during exhaust blowdown there is a short period of supersonic / sonic mass flow.
During the past 30 years maximum power has risen by over 50 %, but the rpm of maximum power has risen only 5 %. The limitation is in the time-area of the ports: the integral of available open port area, multiplied by the amount of time that this area is open.
With the current type of two-stroke engine there is hardly any possibility of raising the power by raising the rpm. The total circumference of the cylinder is occupied by ports; there is no room for any more transfer area.
I have developed a different scavenging principle that seems promising. Jan Thiel thinks: 'It is the only way to make another big step forward in two-stroke development'. I will keep you informed.

Thank you so much for this complete and very interesting answer, Fitz!

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Si nécessaire, quelqu'un traduira en français.

Frits Overmars a écrit:

Like Toopack says: the gas velocity is subsonic. Not only in the intake, but everywhere in the engine. Only during exhaust blowdown there is a short period of supersonic / sonic mass flow.
During the past 40 years maximum power has risen by over 50 %, but the rpm of maximum power has risen only 5 %. The limitation is in the time-area of the ports: the integral of available open port area, multiplied by the amount of time that this area is open.
With the current type of two-stroke engine there is hardly any possibility of raising the power by raising the rpm. The total circumference of the cylinder is occupied by ports; there is no room for any more transfer area.
I have developed a different scavenging principle that seems promising. Jan Thiel thinks: 'It is the only way to make another big step forward in two-stroke development'.
I will keep you informed. But it may take some time....

I have seen experimental cylinders with transfer ports below the exhaust port, then the exhaust port as a ring of ducts above the transfer ports. Is that the type of cylinder your refering to?

Have you a chance to ask H Thiel about the aiming of the transfer ducts? The RSA auxilary ducts aim directly at the exhaust port and the main transfers aim at the boost port. I am assuming it is to provide turbulence, and filling and scavenging under the boost port stream?
I am also wondering about your sub exhaust ducts and the optimal ratio of port window area to duct area?


J'ai vu expérimental bouteilles avec transfert ports ci-dessous l'échappement port, puis l'échappement port comme un anneau de conduits ci-dessus le transfert ports. C'est que le type de bouteille votre réfère? Avez-vous la chance de poser H Thiel au sujet de la visant le transfert conduits? Le RSA auxiliaire conduits visent directement à l'échappement port et les principaux transferts visent à l'impulsion port.

I could ask Jan Thiel about the aiming of the transfer ducts, but I suppose he is watching this forum so there is no need to pass your questions on to him; he reads everything but doesn't react very often.

One thing you do not want in the scavenging flow is turbulence. You want to expel the exhaust gases, not mix them with the fresh charge. What you are looking for in the transfer streams, is that they collide in the center of the cylinder, slow each other down and form a single column with a high density and a low velocity, that rises to the head and at the same time expands in diameter and pushes burnt gas into the exhaust ducts.

There is hardly an optimal ratio of duct area to port window. I generally try to obtain a value of 1,5 but when you look at the B-transfers of an Aprilia (A is the set nearest the exhaust; then come the B-ports, then the C-port opposite the exhaust) you will see that the entry at the cylinder base is almost a rectangle, with a width of 19mm and a 'length' (in riding direction) of 16 mm; that gives 304 mm².
The B-window in the cylinder wall has a width of 25 mm, a height of 13,2 mm and an upward angle of 10°; the effective port area is 325 mm²; it's bigger than the entry area 8).
That may seem strange, but remember that the entry area is open all the time and the port is not...

Below are some pics of a cylinder layout with FOS-scavenging. The two exhaust ducts point sideways.

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Ce qui est ennuyeux, avec Frits, c'est que tous nos réponses vont commencer par "UN GRAND MERCI!"



Frits, I hope that you understand that it is a joke...

very very very ingenious interesting stuff !!!!

I am impatient to see it taking life

Je connaissais ça dans le même genre !
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ce n'est pas du rsw ou rsa mais ça reste dans le même esprit .

Marc a écrit:

Frits, I hope that you understand that it is a joke...

Oui, j'ai compris 8)

Toopack a écrit:

I am impatient to see it taking life.

Me too :lol:

Frits!!

Very nice!

Hello ,

Avec moins de lumières d'échappement , il y a un SAE paper 2006-32-0061 qui montre un cylindre comme ceci :
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L'auteur assure qu' après un peu de développement et sur un banc de controle de balayage uniquement , les performances avaient atteint +/- celles d'un Honda RS125.

Mais il n'a jamais tourné , alors ?....

Slts

With the design shown by 2T4T, you obtain more angle-area for the transfer ports, but less for the exhaust... You really must utilize both sides of the cylinder for exhausts if you want to raise the maximum rpm for optimal scavenging. And with opposite exhausts you need symmetrical transfers that create a stable central scavenging column, otherwise a great deal of the fresh charge will short-circuit into one of these exhausts.

The pictures below show the effective port areas and the angle-areas for the Aprilia RSA-125 with conventional ports and for the FOS-125 with symmetrical ports.
The ratio between the two transfer angle-areas gives an impression of the rpm that should be attainable...

The transfer timing is about the same for both cylinders and the exhaust timing of the FOS is lower than that of the RSA; the RSA-exhaust timing is a compromise between a timing that is too high for optimum resonance and an angle-area that is too small for the rpm that the transfer ports permit.

With the FOS-system I do not need to compromise because I have 23 % more exhaust blowdown area and 33 % more blowdown angle-area, even with the lower timing. And all of the exhaust area is above the transfer ports, contrary to the RSA where 1/3 of the exhaust area is situated too low to be of any use for the exhaust blowdown phase.

Another advantage: because the cylinder is symmetrical, it will not distort under temperature influences. This makes the piston very happy .
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le bruit n'as pas changé, c'est déjà bon signe

pierre a écrit:

le bruit n'as pas changé, c'est déjà bon signe

C'est le genre de truc à se cuire les jambons !

But to be serious, it's a really nice system with the 2 exhaust.

Just 1 question : if there are 2 exhaust on each side, is it working with 1 or 2 intake and with 1 or 2 carburators to be symetric and fill the volume as much as possible ?

Frits Overmars a écrit:

I could ask Jan Thiel about the aiming of the transfer ducts, but I suppose he is watching this forum so there is no need to pass your questions on to him; he reads everything but doesn't react very often.

One thing you do not want in the scavenging flow is turbulence. You want to expel the exhaust gases, not mix them with the fresh charge. What you are looking for in the transfer streams, is that they collide in the center of the cylinder, slow each other down and form a single column with a high density and a low velocity, that rises to the head and at the same time expands in diameter and pushes burnt gas into the exhaust ducts.

There is hardly an optimal ratio of duct area to port window. I generally try to obtain a value of 1,5 but when you look at the B-transfers of an Aprilia (A is the set nearest the exhaust; then come the B-ports, then the C-port opposite the exhaust) you will see that the entry at the cylinder base is almost a rectangle, with a width of 19mm and a 'length' (in riding direction) of 16 mm; that gives 304 mm².
The B-window in the cylinder wall has a width of 25 mm, a height of 13,2 mm and an upward angle of 10°; the effective port area is 325 mm²; it's bigger than the entry area 8).
That may seem strange, but remember that the entry area is open all the time and the port is not...

Below are some pics of a cylinder layout with FOS-scavenging. The two exhaust ducts point sideways.

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Merci Fritz,
Thanks for sharing that information. How important is duct shape to enable the intake transfer streams to slow enough to form the central rising column?

Regarding the FOS cylinder what will be the best method of induction ? Would triple exhaust ports be an improvement on the bridge port?


Merci de partage que l'information. Comment est l'importance gaine forme pour permettre l'admission transfert les flux de ralentir assez pour former les hausse centrale colonne? En ce qui concerne la FOS cylindre quelle sera la meilleure méthode de l'induction ? Serait triple échappement être une amélioration sur le pont port?

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They make good lampshades

Institute of TwoStrokes a écrit:

How important is duct shape to enable the intake transfer streams to slow enough to form the central rising column?

The ducts should provide an easy path for the fresh charge with as little pressure loss as possible. Not only the cross-section and the radii, especially the inner radius, but also the duct length plays a role. On a flow bench with a constant stream of air you cannot measure this; you need a pulsating air stream to establish the effect of the length.
The ducts should deliver the charge in dense jets, in the desired direction into the cylinder. Here too the inner radius of the ducts is important.
The slowing down of the charge jets is not a job for the ducts; the jets should slow each other down when they collide in the cylinder.

Citation :

Regarding the FOS cylinder what will be the best method of induction ?

The best method of induction, when you consider the conventional solutions, is a rotary valve. But there are also unconventional possibilities; I am working on a system that I call the 24/7-inlet. I will explain later.

Citation :

Would triple exhaust ports be an improvement on the bridge port?

A bridge port like in a Honda RS has two disadvantages. It is relatively long which hinders the heat transport to the surrounding metal, and it is in the thrust face of the piston, which is all the more undesirable because any lubricating oil is blasted off by the hot exhaust gases.
In my cylinder the bridges are much shorter, and they are on the sides, not in the thrust areas.
Apart from the problems with a conventional central bridge it is desirable to have as few bridges as possible, because each bridge is a heat exchanger: it absorbs heat from the exhaust gases and passes this heat on to the fresh charge that has entered the exhaust duct and is subsequently pushed back into the cylinder by the exhaust pulse. This charge should be as cold as possible when the exhaust closes and compression starts.

Hello, interesting !!
Your system looks like in a certain amount, to the big 2T Diesels with the exhaust valves are rond in the head and the inlets ports are all rond in the bottom wall (there is a turbo there...)
I think you are int the good way to improve the cycle , go on