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

The flow capacity is limited by the reedvalve, not the carburettor.
So it makes no sense using a carburettor bigger than 39.
We tried, of course, but it was not better

55 KTM HP is surely at the crankshaft.

Jan Thiel a écrit:: Frits, if you wish you can publish the exhausts sizes at this forum, no problem!

OK, here we go, for all two-stroke addicts: the latest exhaust pipes from Aprilia, Honda, Derbi and KTM.

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Nombre de messages : 60 Localisation : australia Date d'inscription : 01/06/2012

And we all right click, save image as.

Thank you Frits. Im sure there are a lot of snips and torches being used this week as everyone tries these designs. It is very intersting to me that the Aprilia pipe has no parallel center section. This goes against the norm. Was it found that a tapered center carried the negative wave longer thus evacuating more charge through the motor? Also the last section of the difuser cone is very long and has a relatively steep angle. This would indicate a very high suction from this pipe. I am curious as to the name 102Tubo? What does this signify?

Frits Overmars a écrit:

Jan Thiel a écrit:: Frits, if you wish you can publish the exhausts sizes at this forum, no problem!

OK, here we go, for all two-stroke addicts: the latest exhaust pipes from Aprilia, Honda, Derbi and KTM.

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[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked) - Page 38 199739

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked) - Page 38 1993206895

Howard Gifford a écrit:: I am curious as to the name 102Tubo? What does this signify?

102 is the serial number, tubo is Italian for pipe Wink

.

Invité

So incredible men to work such a lot and then to share your work . I am was a fan of what you made , now I am fan of who you are .
[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked) - Page 38 1993206895

MANY THANKS FOR THAT MEASURE....I WILL TEST THEM

Hi Frits and Jan,
I can only speak for myself but it is obvious from the forum that we all hold you two men in high regard both as authorities on the subject of two stroke knowledge but also as generous human beings who enrich the lives of others. Thank you very much for sharing your knowledge with us.
Many thanks again.

Jan Thiel a écrit:: The flow capacity is limited by the reedvalve, not the carburettor.
So it makes no sense using a carburettor bigger than 39.
We tried, of course, but it was not better

55 KTM HP is surely at the crankshaft.

Hi Jan and Frits,
Yamaha has quoted that the reed valve should be about 90% of the flow rate of the Carburettor to keep a good flow rate; is this what you have found or is it a higher figure?

I like Frits' idea of the 24/7 reed valve, but it seems to me that only an electronic actuated 24/7 reed valve could response faster enough to provide the power range that we need in motorcycling. Am I wrong in this thinking?

Thank you again for your time. [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked) - Page 38 241515

GtG001 a écrit:: ....I like Frits' idea of the 24/7 reed valve, but it seems to me that only an electronic actuated 24/7 reed valve could response faster enough to provide the power range that we need in motorcycling. Am I wrong in this thinking?

In the 24/7-system the reed valve serves to start the engine and to keep it running until it comes into its power band. Once the exhaust resonance sets in, the reed valve is no longer necessary and can be swung out of the way of the inlet flow. That does not require a fast response time at all.

Let's take an example of an engine where the power band starts at 10.000 rpm. Then the reed valve should remain in function until at least those 10.000 rpm. But if it is still there at 10.500 rpm, that only means that the engine is still running as a reed valve engine instead of a 24/7-engine. In this transition phase where exhaust resonance is setting in, the power difference will be minor.

The 24/7-system will be electronically actuated because that is the simplest way to do it. But it could as well be done centrifugally, like an early exhaust power valve. In fact the 24/7-system should be opened at about the same rpm as such an exhaust valve.

Hi Frits. I am a bit skeptical about your 24-7 idea. Perhaps you could enlighten me as to how it will help power output. It is my experience that a rotary valve engine loses power with closing after 105 degrees. A 24-7 design has no closing. I have tested up to 135 degrees closing. Using my variable timing to start the motor I have found a large drop in power starting at 110 degrees increasing to where the motor loses 10 hp at 135 degrees closing and is very sluggish to respond at lower than optimum rpm. I can not start the motor with anything over 135 closing (110 closing with the variable timing at full advance) Does your design rely solely on intake resonance to operate?

It does rely on the reed valve for starting, so that is one problem out of the way. It does not rely on intake resonance at all, as there is no intake resonance as such. A racing two-stroke engine is a compound resonance system because all ports are open simultaneously at one time or another. Flow through the engine is mainly governed by the exhaust system but a lot of other factors come into play; you cannot separate the inlet part.
Your experience with late inlet closing is valid for your engine, no doubt, but what crankcase volume did you use? That is one of the important factors where the 24/7-system probably differs a lot from conventional engines.

I regret to say that I have just blocked my private message-option. Dealing with private messages was taking up ever more of my time and finally I simply could not answer all questions any more.
To those of you who sent me private messages: please do not feel offended. I can very well understand your desire to ask all kinds of questions; I would probably do the same if I were in your position. But I hope you can also understand my position.
I will gladly continue to answer any questions that are asked in public, in the forum, so that all forum members can take notice.
Sincerely,
Frits Overmars

Thank you, Frits!

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Nombre de messages : 27 Localisation : lyon Date d'inscription : 19/11/2011

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Hello Mr OVERMARS

I watch your topics with interest.
On a other topic you had put drawing of RSA cylinder.I have many question:

When you watch drawing "SEZIONE AA" the A-port is at left and B-port at right that's good?

If A-port is at left, when I watch drawing angular to exit port is more important than B-port?
Principal transferts are more inclination than auxiliary transferts is that.

I see also that B-port (90-42)is higther than A-port (90-43.1) it's right?

For finish witch values did you have at timing transfert port and exhaust port with valve open in this cylinder?

Thanks for answer

Mr MINGRET

MINGRET01 a écrit:: When you watch drawing "SEZIONE AA" the A-port is at left and B-port at right that's good?

Yes

Citation :: If A-port is at left, when I watch drawing angular to exit port is more important than B-port?

No. It's not more important, but it is larger, if that is what you mean.(this may be a language problem).

Citation :: I see also that B-port (90-42)is higther than A-port (90-43.1) it's right?

Yes

Citation :: For finish witch values did you have at timing transfert port and exhaust port with valve open in this cylinder?

Exhaust 202°, A-transfers 130°, B- and C-transfers 132°.

Nombre de messages : 62 Localisation : Denmark Date d'inscription : 12/02/2012

MINGRET01 a écrit:: [Vous devez être inscrit et connecté pour voir cette image]

Hello Mr OVERMARS

I watch your topics with interest.
On a other topic you had put drawing of RSA cylinder.I have many question:

When you watch drawing "SEZIONE AA" the A-port is at left and B-port at right that's good?

If A-port is at left, when I watch drawing angular to exit port is more important than B-port?
Principal transferts are more inclination than auxiliary transferts is that.

I see also that B-port (90-42)is higther than A-port (90-43.1) it's right?

For finish witch values did you have at timing transfert port and exhaust port with valve open in this cylinder?

Thanks for answer

Mr MINGRET

Do you've a link to to a high resolution picutre? It's almost impossible to read most of the measurements

Nombre de messages : 27 Localisation : lyon Date d'inscription : 19/11/2011

Thank Mr OVERMARS for your answers.

By angular ,I means the inclination where transferts exit to cylinder.see drawing following:

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On drawing "SEZIONE AA" angular for A-port is 28.16° and for B-port is 6.82°.Is exact or the both transferts are the same angular?

Mr MINGRET

Dear Jan and Frits... definitly [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked) - Page 38 241515

Invité

Frits Overmars a écrit:: I regret to say that I have just blocked my private message-option. Dealing with private messages was taking up ever more of my time and finally I simply could not answer all questions any more.
To those of you who sent me private messages: please do not feel offended. I can very well understand your desire to ask all kinds of questions; I would probably do the same if I were in your position. But I hope you can also understand my position.
I will gladly continue to answer any questions that are asked in public, in the forum, so that all forum members can take notice.
Sincerely,
Frits Overmars

Thank you frits [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked) - Page 38 727249

[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked) - Page 38 980796

Nombre de messages : 55 Localisation : Germany Date d'inscription : 20/02/2012

I see, that the "back pushing" cone of the Aprilia exhaust has got 3 parts, first one with the lowest angle and third one with the highest. Is this to make the power band more "symmetrically" (more torque to lower revs and less torque to higher revs) or does this also bring more maximum power than a cone with one and the same angle?

Regards

MINGRET01 a écrit:: By angular ,I means the inclination where transferts exit to cylinder.
On drawing "SEZIONE AA" angular for A-port is 28.16° and for B-port is 6.82°.

You just answered your own question Wink

.

Daniel A. a écrit:: I see, that the "back pushing" cone of the Aprilia exhaust has got 3 parts, first one with the lowest angle and third one with the highest. Is this to make the power band more "symmetrically" (more torque to lower revs and less torque to higher revs) or does this also bring more maximum power than a cone with one and the same angle?

The three-part reflector is a relic of evolution, like an appendix. I think a single cone can be just as effective.

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