[GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 3) (Locked)

Ian Harrison a écrit:

So why didn't the dyno operator maximise both the red and blue curves to give the best (and obviously equal) results up to 12,000 rpm?

exactly my thought!? the curves also differ before 12.000 rpm and even the stock one has a better overrev than 100% energy...

Frits Overmars a écrit:

Just a thought: could it be that the weakening of the spark is accompanied by a longer duration of the spark?

Borut told me that he did not conduct the measures.
I asked him if he can perform the measurements, he told me that he will execute them.
It does not have a coil TZ250, I'll send him one of mine.
(*ITA - Borut non ha avuto modo di eseguire le misure con la scintilla con potenza ridotta. Gli ho chiesto se può eseguirle, mi ha detto di si. Non ha però le bobine del 250 a disposizione, gli invierò una delle mie *)

Borut has performed several measurements with different coils with the ECU Zeeltronic standard (power 100%). There are considerable differences in duration and spark voltage.
I have the documentation, he told me that I can publish them freely. The file is in Word format, someone can upload it to a server?
(* ITA - Borut ha eseguito differenti delle scintille con differenti bobine con la sua centralina standard (potenza 100%). Ci sono notevoli differenze di comportamento nella tensione iniziale, tensione massima e nella durata della scintilla.
Mi ha inviato la documentazione grafica, mi ha detto che posso pubblicarla liberamente. Il file è in formato word, qualcuno ha la possibilità di caricarlo su un server? *)

Borut explained to me the difference before 10000 rpm. He thinks that his units hold the energy constant. Instead the ECUs Yamaha decrease the energy to rise the revs.
Borut change the TZ unit to give the possibility to increase the energy of the first spark of 10000 rpm.
(* ITA - Borut ha provata a interpretare la differenza di rendimento prima dei 10.000 giri. Secondo lui la differenza può derivare dal fatto che con le sue centraline ha sempre mantenuto l'energia della scintilla costante. Invece la centralina TZ250 della Yamaha decrementa lentamente l'energia della scintilla al salire del regime di rotazione.
Borut ha detto che quando troverà il tempo aggiornerà la centralina TZ in modo consetire l'aumento dell'energia della scintilla prima dei 10000 giri *).

Sorry for my bad english.

Muciek a écrit:

If you could please post a video how is that simson running :)

Here you go :) Best value was 28,6 rwhp and 30,4 crank hp until now.

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Daniel leave the throttle on between shifts... you're backing off every shift!

I'm afraid, that the gears could break :/ But I think you are right, I should try it

Hi mRk,
Thank you for the information.
Please be assure I am not trying to discredit Borut in any way; I am just trying to understand the new concept that his product is promoting by asking the obvious question – how does that feature work?

If I understand you correctly; you are saying that the TZ250 CDI has a decline in the spark energy after 10,000 rpm which is a result of the designed but not a feature – and the Zeeltronics CDI is able to hold the spark energy more constant through their better design – this would make more sense.

The peak torque of the 2000-02 TZ250 is quoted as 11750 rpm so this factory CDI reduction would be before peak cylinder pressure.
If Yamaha wanted to change the timing it would be a simple change in the curves as they multiples inside the TZ250 CDI. If they wanted to extend the duration, they would increase the coil windings and energy available. It is common knowledge that most Japanese motorcycle companies make their product to a price and this also includes the consumer racing motorcycle too; so this could account for drop off in spark energy given the production date and that the CDI remained vertically unchanged since the early 1990’s.

To reduce the spark energy near peak torque goes against everything that the Ignition companies of the world have said for a long time. MSD (America) push the fact their unit not only has more spark energy than others but they also have multiple sparking to increase the duration for better propagation – an opposite view to reducing the spark energy.

Having said that, I am always willing to learn from those who have more knowledge and experience

Exactly.

I send the two files to Vagelis. Are graphs of the measurements performed with different spark ignition coils and voltages.
Now I'm leaving for the first race of 2013. My bike participates in the Alpe Adria Road Racing Championship in class 125 SP. I should return Mondays. After returning I will explain the graphics.

voltages.doc

coils.doc

Here are the two files from Marko. Right click on the link and choose save link as. :)

I have a question for Frits. My new rotary valve engine makes big power but it only makes good power with the VM34 mm carbs with ridiculously late closing timing. This makes it extremely hard to start. To overcome this I developed a variable timing system but even with the variable timing the engine is not quick to build revs compared to the reed motor. The original reed motor was a cylinder reed motor but to convert it to rotary valve I cut the reed cages off and welded the hole up and filled the void with epoxy. Thye c port was cast into the epoxy.
My question is ... Is a case reed motor a better design than a cylinder reed motor? I can weld the reed cages onto the case and use all the rotary valve converted cylinders on the case reed motor. Or should I scrap the whole idea and just work with the cylinder reed motor?

Howard...

A case reed motor is definitely a better design than a cylinder reed motor but generally speaking a rotary valve motor is better still, Howard. In your particular case however the obligatory small carbs throw a spanner in the works.
Shortening the inlect tracts will help but since the carbs have only half the area they ought to have for your engine, a late closing timing seems unavoidable. Case reeds may be the easy way out.

Thanks Frits. You are the best... One question... What time is it where you are? my calculation says 3:00AM

Frits, will there be a 3rd episode of the 'mr.FOS holiday education' article series?? Would you have the free time?

Howard Gifford a écrit:

Thanks Frits. You are the best... One question... What time is it where you are? my calculation says 03:00AM

Nah, it must have been about 02:00 AM. Oh well, I'll sleep when I'm old.
'm posting this at 10:16 AM dutch daylight saving time.

Vagelis a écrit:

Frits, will there be a 3rd episode of the 'mr.FOS holiday education' article series?? Would you have the free time?

Don't hold your breath, Vagelis. Holiday for me means: holiday .

Speaking of which: is anybody planning to come to Mettet on monday 13 may to witness the birth of the Freetech50 class ( [Vous devez être inscrit et connecté pour voir ce lien] ) ? I'll be there and I know so will be a lot of interesting people and machines.

Frits Overmars a écrit:

Howard Gifford a écrit:

Thanks Frits. You are the best... One question... What time is it where you are? my calculation says 03:00AM

Nah, it must have been about 02:00 AM. Oh well, I'll sleep when I'm old.
'm posting this at 10:16 AM dutch daylight saving time.

Vagelis a écrit:

Frits, will there be a 3rd episode of the 'mr.FOS holiday education' article series?? Would you have the free time?

Don't hold your breath, Vagelis. Holiday for me means: holiday .

Speaking of which: is anybody planning to come to Mettet on monday 13 may to witness the birth of the Freetech50 class ( [Vous devez être inscrit et connecté pour voir ce lien] ) ? I'll be there and I know so will be a lot of interesting people and machines.

I am coming, and I hope that lots of people will do the same. This initiative is a good one and should get alll the necessary support from those who really want two stroke road racing to get once again its place that was robbed by the FIM and national sanctioning bodies.
The new circuit of Mettet is a very good choice for a start. It is not far from the northern region of france, lots of motorcycle enthousiasts know it from the famous Superbiker race. For example : 148 km from Lille.

Je pense sincerement que c'est une occasion a ne pas louper. Le développement du 2T 50 cc est historiquement très liée aux hollandais qui ont toujours été les meilleurs préparateurs et amateurs de cette classe disparue. Un petit groupe de gens essai de revitaliser cette classe, en faisant preuve de beaucoup de bonne volonté, de volontarisme mais aussi de réalisme. Pas de grandes déclarations, mais de épreuves sur de vraies circuits en non sur des pistes karting. Avec une réglementation qui n'étrangle pas la technique mais bien au contraire la laisse prospérer.
Moi en tout cas, j'espére pouvoir serrer la main et faire connaissance de certains gens qui ont marqué la grande époque du 50 cc et qui veulent résusciter cette belle classe.

Et nous faire un CR....

Fin du

I have one more question.

How much ist the clearance between carbon rotary valve and his housing (I hope that you know what I mean )
Diameter of the rotary valve is 120mm and thicknes is about 0,4- 0,45mm
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thanks

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Ciao Stefano, come stai?
Everything is different between the Aprilia RSA125 engine and the 100cc kart engine. I think you have been able to find sufficient data regarding the RSA125 in all the forums you are visiting , so I will confine myself to the kart engine.
It has only three transfer ports, with a timing of 134°. The exhaust timing is 187° and there are no power valve, no powerjet and no variable ignition timing.
Both the primary and secondary compression ratios are high and the exhaust pipe is deliberately made low-efficient so that the exhaust pulses do not generate much power, but they do not cause a deep torque dip either.
The axial scavenging angles are rather steep so that at low revs a lot of fresh mixture is washed-through, lowering the exhaust gas temperature and the pipe resonance rpm.
What you would need for your ideal power curve, are a programmable ignition, a power jet and a power valve or, best of all, a trombone exhaust pipe.

alcatelko a écrit:

How much ist the clearance between carbon rotary valve and his housing ?Diameter of the rotary valve is 120mm and thicknes is about 0,4- 0,45mm.

Total clearance should be roughly 0,4 mm. But I am surprised by the disc's thickness of only 0,4 mm. Most carbon discs I've seen are twice as thick....

Mr. Thiel, in more than one occasion you wrote that every single mm2 gained of transfer ports area is good. Have You ever determined what was the minimum width of the bridges between the A-B-C ports? What could be the problem with transfer bridges wide for example 1mm?
Thank you for your answer.

A question for you Frits
Concerning exhaust systems , all calculation we do are doing on linear exhausts so my question is,
how do you convert a linear shape and design to a no linear one for keeping characteristics from calculations?
What would be the most important? Example on a diffusor.

Keeping the volume after shaping?
Keeping the same length on the neutral fiber.. or something else?
Of course i know in any case it will be after, testing and testing....
Thanks for your answer
Pierre

Frits Overmars a écrit:

It has only three transfer ports, with a timing of 134°. The exhaust timing is 187° and there are no power valve, no powerjet and no variable ignition timing.

Frits, are you sure about the exhaust timing ? In the old ICA the maximum allowed was 177°, I have already seen 182° but not more.
You confirm 123° for A port and 133° for C port ?

pierre95 a écrit:

A question for you Frits
Concerning exhaust systems , all calculation we do are doing on linear exhausts so my question is,
how do you convert a linear shape and design to a no linear one for keeping characteristics from calculations?
What would be the most important? Example on a diffusor.

Keeping the volume after shaping?
Keeping the same length on the neutral fiber.. or something else?
Of course i know in any case it will be after, testing and testing....
Thanks for your answer
Pierre

I corregisquen Messrs. Jan or Frits if I'm mistaken, answering your question, the design is straight in as we know it to optimize the engine, then it is necessary to design with curved frame for retaining all properties of the original design straight in both volume and length and taper, rectitude except obviously.

Formerly (or so I did) was made straight exhaust manufacturer directly and then made ​​the cuts necessary angle and rotates 180 ° to the tube remain turned to the required angle (which is twice the cut initial), as indicated by this image:

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Now everything is done by computer 3D design and development flat of the cone, then laser cut and manufactures tube as the proper curved shape, a design example:

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Sorry for my bad English

roost a écrit:

Mr. Thiel, in more than one occasion you wrote that every single mm2 gained of transfer ports area is good. Have You ever determined what was the minimum width of the bridges between the A-B-C ports? What could be the problem with transfer bridges wide for example 1mm?
Thank you for your answer.

Minimum width is about 1,5mm

Piquer a écrit:

pierre95 a écrit:

A question for you Frits
Concerning exhaust systems , all calculation we do are doing on linear exhausts so my question is,
how do you convert a linear shape and design to a no linear one for keeping characteristics from calculations?
What would be the most important? Example on a diffusor.

Keeping the volume after shaping?
Keeping the same length on the neutral fiber.. or something else?
Of course i know in any case it will be after, testing and testing....
Thanks for your answer
Pierre

I corregisquen Messrs. Jan or Frits if I'm mistaken, answering your question, the design is straight in as we know it to optimize the engine, then it is necessary to design with curved frame for retaining all properties of the original design straight in both volume and length and taper, rectitude except obviously.

Formerly (or so I did) was made straight exhaust manufacturer directly and then made ​​the cuts necessary angle and rotates 180 ° to the tube remain turned to the required angle (which is twice the cut initial), as indicated by this image:

[Vous devez être inscrit et connecté pour voir cette image]


Now everything is done by computer 3D design and development flat of the cone, then laser cut and manufactures tube as the proper curved shape, a design example:

[Vous devez être inscrit et connecté pour voir cette image]


Sorry for my bad English

Every bend made in an exhaust pipe has some influence on power.
Sometimes quite a lot.
Nearly always the power is worse!
So be very careful, and, if possible, always compare with a straigt pipe!