[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 5)

My 2-stroke spreadsheet is ready  (for now at least), so I'm throwing it on the net so everybody can use it.
It contains pages for ports, the head and FOS pipe
On the seperate ports pages (exhaust and transfer),  it calculates the STA numbers (Specific Time.Area) of your ports and you can matcch them to the target's, determinned by the BMEP
On the Head page, you can design your head and it calculates the MSV (Mean Squish Velocity) 100% accurtly with Blair
On the FOS-pipe page, it calculates a Frits Overmars FOS pipe, and you can ad a Wobbly-duct , and you can add extra header/diffusor/baffle sections to the pipe.

you are free to do with it what you want, as long as it is not for commercial use. If somebody has idea's to improve or add extra features, please share so we can all benefit.
In the manual I've tried to explain how it works, please read it first before you ask questions.
If anybody has any clue on how to print portmap's to actual size, please let me know, as I have absolutly no idea.

En francais :
mon tableau excel 2-temps est prêt, donc je le met disponibles pour tous le monde.
Il y a des pages pour les portes (échapement et transfert) qui calcules les Time.Area Spécifique et vous pouvez modeler vos portes qu'ils correspondent avec les objectifs déterminés par le PME
Il y a une page pour modeler la chambre de combustion
et une page qui calcule des échapement FOS par Frits Overmars, ou vous avez la possibilité d'ajouter un "Wobbly-duct" et des troncon? en plusieurs parties.

vous pouvez faire avec l'excel ce que vous voulez, que pour des l'utilisations commerciales. si quelqu'un a des idées pour l'amméliorer, laisse nous savoir que tous le monde s'en peut profiter.
Désoler qu'il n'y a pas de manuel en francais, ce serait trop compliquer pour moi et peut être vous n'en comprendré rien du tous Si quelqu'un a envie de le traduire ... ?
si quelqu'un sait comment imprinter des "portmap" en "taille réelle", laisse moi savoir svp, parce que pour le moment j'ai aucune idée.

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manual : [Vous devez être inscrit et connecté pour voir ce lien]

double

Merci JanBros !

JanBros a écrit:

My 2-stroke spreadsheet is ready  (for now at least), so I'm throwing it on the net so everybody can use it.... you are free to do with it what you want, as long as it is not for commercial use.
excel : [Vous devez être inscrit et connecté pour voir ce lien]
manual : [Vous devez être inscrit et connecté pour voir ce lien]

Bravo Jan! I know that it has been a tremendous amount of work.
I noticed that you refer to my 'Leaning Tower of Pisa' story. If you wish, you can download the complete Pisa-story from [Vous devez être inscrit et connecté pour voir ce lien] , from the folder 'FOS Tips & Concepts', and bundle it with your masterpiece. In fact, you can use everything you find there and use it, provided credits are respected.
You might also take a look at the disclaimer accompanying the 'FOS Exhaust Concept'; it is a little more extensive than the older version that you quoted.

apparently I seem to make the same mistake over and over : I keep forgetting the variable for the FOS pipe is speed of sound and not exhaust gas temperature. It had no effect on the workings of it all, but I've corrected it now in the manual and the spreadsheet and uploaded corrected versions ;-)

apparament, je fait le même erreur toujours : c'est pas le température du gaz de l'échapement, mais la vitesse du son (?) qui est le variable dans le concept FOS pour les pipes. ça ne changerait riens pour les calcules, mais je l'ai changer maintenant dans le manuel el l'excel et mit en ligne des versions correct.

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Great work !

Good morning All!

I have a question for Frits about the Helmholtz resonator concept.
Can we consider that the attempt from Yamaha with the YEIS system fitted on a certain number of road bikes is an exploitation of this concept?
If yes, is there a way to make it really work (I understand from what I could hear or read that it is not making any outstanding difference in performance)?

carlovitch1 a écrit:

Good morning All! I have a question for Frits about the Helmholtz resonator concept.
Can we consider that the attempt from Yamaha with the YEIS system fitted on a certain number of road bikes is an exploitation of this concept? If yes, is there a way to make it really work (I understand from what I could hear or read that it is not making any outstanding difference in performance)?

Good afternoon Carlovitch1. The physics principles decribed by Hermann von Helmholtz do play a role in the functioning of the Yahama Energy Induction System, but the aim is somewhat different. A Helmholtz resonator is usually applied with the objective of achieving the strongest possible resonance at a given frequency; the YEIS was developed to spread useful power over the widest possible range.
There is a way to make it work, but I feel I have already tried to explain this a thousand times, so you may have to do some searching yourself. Maybe this helps:
Google can search for a specific search term in a specific website with the site: function. For example:
Yamaha YEIS site:http://www.pit-lane.biz
And if all goes well, you will find something like this:
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OK, thanks a lot Frits for your quick reply !
I was really doubtful about whether this YEIS was a marketing gadget or something valid, potentially useful. Looks like there was some research behind it because there's a SAE publication (N° 810923) about it but I did not purchase it (maybe someone has it?).
Thanks for the links, I will dig by myself.

Hallo,

right as I´m nearly finished with my own Powerjet someone offered me 2 Dellorto VHSJ42 carburettors including the calculation programm.
Got someone here information about these carburettors? I´m glad about every information. (jetting, parts, history, ...)
The carbs use the GP-atomizer, got pulsed PJ, a special formed slide, use AK-series needles and are cast magnesium.
Someone got a source for jetting parts?
Best regards,
Bernd
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Did you try to simply contact Dellorto ?https://www.dellorto.it/it/prodotti/carburatori/

Mrs. my compliments
In particular to Mrs. Jan Thiel and Frits Overmars,for sharing all your experiences and knowledge with all the enthusiasts participating in this forum.
My name is Leonardo Faustino Ferreira,
I have a modest company dedicated to racing motorcycle performance optimization services, in the city of São Carlos in Brazil.

Initially I developed my expertise in 4 stroke engines, however the superior performance of our beloved 2 stroke engines made me research and very lucky to find this amazing forum and get even more impressed with the 2 stroke engines by knowing the efficiency and power of the Aprilia RSA 125.

Sorry for my English

I read and tried to understand and develop everything that was posted in this topic, but I don't remember seeing, Aprilia RSA RPM power valve opening data,
I wish to develop a method for calculating the opening start point and its progression,
If this is a stupid idea let me know

Bem-vindo Leonardo e obrigado por suas amáveis palavras. A propósito, seu inglês é perfeito.
The power valve started opening at 10.000 rpm and it was fully open at 12.000 rpm. I must have a list of the intermediate steps somewhere at home, but as I will be abroad for some time yet, I have no access to those data at the moment.
You made me curious about your racing motorcycle performance optimization services. It would be nice if you could tell and show us some more about it.

Thank you Frits,
let me know when you have access to the list of intermediate power valve steps, it will be of great importance, as will all the technical information of the Aprilia RSA_125.
My works are dedicated to amateur team competition motorcycles, the biggest motorsport championship here in Brazil has only two categories with free engine development and they are 600cc and 1000cc 4 stroke, which is very discouraging, the development if not there is, however we have regional championships with super motard racing, drag racing and motocross racing,
we have a handcrafted flow bench and dynamometer,
I am completing flow bench upgrade, to a pressure of 90 [inH2O] near 225 [mBar] for small diameters.
I always use the highest possible pressure, especially on 2-stroke engines, at least above the fully turbulent flow line,
I read somewhere in this topic about the impossibility of reaching operating pressure and was very curious about the pulsed flow bench ... is this still a secret?
I did some tests in an attempt to build a pulsating system but still couldn't evaluate the repeatability of the results.

Leonardo, the pulsating flow bench is not really a secret any more; the principle has been around for some time now.
Here is a picture of the pulsating bench built by my friend Andrea degli Esposti (DEA).[Vous devez être inscrit et connecté pour voir cette image]

After 25 years of flowbench experience I think that the engine itself is the very best flowbench…..
Flowing transfer ducts is useless!
As is the 'Jante sysrem'.

Summed it all up,
"the engine is the best flow bench!"
I agree, Mr. Jan, I get good results on 4-stroke engines, where the flow optimization interferes more directly, I believe that most of the air mass is demanded by the piston and the flow direction is less important, even For turbulence generation, benchtop test results such as tumble go in the same direction as practical tests, in this case for combustion efficiency (generally tumble increases pressure drop and decreases power),
However, I have no doubt in saying that on 2 stroke engines, the application of the free teachings on this topic has greatly increased the power of my 2 stroke engines, than on bench tests except the exhaust port and carburetors, that seem to be more dependent on a more organized flow.
I have a lot of questions for "2-stroke Doctors"
But I will make one that, I don't remember seeing here, what is the material used in the pipes the Aprilia RSA 125 and the thickness of this material,
And the opinion of Mr. Jan Thiel and Mr. Frits Overmars on the materials available for exhaust systems

Aprilia exhausts were made by SAMBA in the Netherlands.
We faxed a design to SAMBA, and the exhaust arrived within 3 days.
If it was straight, pipes with bends took a little longer.....
For testing straight pipes were used on the dyno, normal, cheap steel was used.
Pipes that had to fit on a bike were mostly made of titanium.
The curved part 1mm, the rest 0,7mm thickness.
Titanium pipes were a lot lighter, which was the main reason for their use.
Curves in pipes can cost a lot of power, but a straight pipe does not necessarily give more power!!
So 'cut and weld' remains the only good solution.
That can take years….
And then, fitted on the bike the air stream on the pipe can still make a big difference!
It really is quite complicated, especially if you have more than 1 cylinder....
There were exhaust flanges of different length's, to adjust the length to local temperatures.
To complicate things even more there was carburetor setting, variable ignition and powerjet curves.
All adjustable PER GEAR!!!!!
Over the years several 100K testing km's were done, on various tracks
When I arrived at Aprilia there was a 5-man team. exclusively for 259cc testing!
Quite an experience after working for many years in teams with at maximum 4 people, including myself!
In those times work was never really finished, and there was no testing ever possible.
In the end this system failed terribly, as was unavoidable, even working day and night.
But some people never understood....
I once worked for a complete fool, who thought you could win with only 2-3 people.
Of course we failed hopelessly, even with the help of Frits.
And it was the most stupid thing I ever did...….
I still regret the lost time!!!!!!!!

LeonardoMRF2 a écrit:

what is the material used in the pipes the Aprilia RSA 125 and the thickness of this material, and the opinion of Mr. Jan Thiel and Mr. Frits Overmars on the materials available for exhaust systems?

Here are some titanium Aprilia pipes, and the sheet material that was used: titanium Grade 2, thickness 0.24" (that's 0,6 mm in real money).
Titanium has the advantage of its low weight and also of its low heat conductivity and its low specific heat, which results in pipes that heat up quickly and do not loose much heat to the environment. The downside is that titanium is a quite stubborn material. It does not like to be bent and it needs welding in a protective gas atmosphere. Stainless steel is slightly easier to process and shows a similar heat conductivity behaviour.
The graph below shows the effect of three different materials for pipes with identical dimensions on one and the same engine.
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Good afternoon and happy new year to all and your families !

Thanks for these interesting info, Jan and Frits.

About the pipe material selection, being a materials engineer (for pressure vessel engineering, not vehicles), I'm a bit surprised that stainless steel is considered. Is this austenitic SS like 304/316L or a specific grade? Austenitic stainless steel does not like vibrations and is also very sensitive to cold work effects compared to carbon steel. My idea was that they will not last long.
If you look at MX bikes, for example, you will never find SS pipes on them, although this would be a good alternate to chrome plated carbon steel in terms of corrosion resistance.
Or maybe the pipe lifetime is short enough at this racing level to take this parameter out of the main concerns?

Happy new year to all,
Thank you Mr. Frits and Mr. Jan,
Thanks again for sharing this important information,
Mr. Jan Thiel, if I'm not wrong, was informed that after testing, there was no point in developing a powervalve system for the auxiliary exhaust ports at Aprilia RSA 125,
In some other engine that worked the power differences were more significant, also lowering the auxiliary exhaust ports.
Mr. Frits has some tests that worked to justify a more complex powervalve project in 3 exhaust ports.

carlovitch1 a écrit:

I'm a bit surprised that stainless steel is considered. Is this austenitic SS like 304/316L or a specific grade? Austenitic stainless steel does not like vibrations and is also very sensitive to cold work effects compared to carbon steel. If you look at MX bikes, for example, you will never find SS pipes on them...

You are right Carlo. Building a pipe out of welded segments does not require much cold deformation, but building a pipe from pressed shell halves is another matter, so stainless steel is definitely not suitable for mass production pipes. And neither is titanium.

Thanks for your confirmation, Frits.
I will try a cone pipe out of SS on one of my projects, just for fun.

Surprising: a lot of 4 strokes exhaust silencers are made of S. steel, included tubes pipes, without Pb of cracks.
Dan

Maybe the use of standard tubes (for 4 strokes) is reducing the vibration issue. 4 strokes pipes shapes are generally less complex than 2 strokes ones.