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

Jan I am curious as to how you examined the 'pressure-time history'(not sure if that is the correct term you would use) of the engine with out any software? Did you have an array of stategicaly placed Kistler transducers?

Jan je suis curieux de savoir comment vous avez examiné la «pression-temps l'histoire»(pas sûr si c'est le terme exact que vous utilisez) du moteur avec tout logiciel? Vous avez un tableau de stategicaly placé Kistler transducteurs

Marc a écrit:

Is there any pic of this time? I mean, not specialy pic of the engine, but the small team who worked in Spain, the workshop,... Any "anecdote" would be highly appreciated...

I have just one digital picture, but it is an historic one: it is the first sketch of the engine we now know as the RSA125:

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

You can see three small circles and a part of a big circle. The top circle ist the gudgeon pin in the piston; the circle vertically under it is the big-end pin. The circle at the left with the arrow in it and the text 'contralbero' is the balance shaft. The partially visible big circle is the crankshaft. From the balance shaft to the right runs a shaft with the text 'centro albero comando valvola'; this is the shaft that drives the rotary disc, indicated by the 'A'.
Bottom right, Jan wrote the date of birth of this engine: 19 september 2004.

Institute of TwoStrokes a écrit:

Jan I am curious as to how you examined the 'pressure-time history'(not sure if that is the correct term you would use) of the engine with out any software? Did you have an array of stategicaly placed Kistler transducers?
Jan je suis curieux de savoir comment vous avez examiné la «pression-temps l'histoire»(pas sûr si c'est le terme exact que vous utilisez) du moteur avec tout logiciel? Vous avez un tableau de stategicaly placé Kistler transducteurs

You want transducers, Lawrence? Here you go:
[Vous devez être inscrit et connecté pour voir cette image]

But this is not a picture from the Derbi racing department. As Jan explained, there was electric light and running water at Derbi, and not much more... (apart from a very amicable atmosphere).
At Aprilia, on the other hand; there were a lot of things, but not a great atmosphere...

Thank you Frits!

This sketch is "highly appreciated", as the beginning of a great story!

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

I am so greatful I found this forum! To be reading pages written by Mr. Thiel and Mr. Overmars is incredible for me. Being in Canada, there is no 2 stroke knowledge which becomes actually designing and building 2 stroke engines. I have read and re-read the 37 pages of posts and always look for more.

My company builds 2 stroke engines for kart racing. Like Mr. Payart of FPE, we build a disk valve twin cylinder 250cc Superkart engine. Just recently we designed and build a 150cc fixed gear engine for American dirt track Karting.

Here are some pictures:

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

Welcome on board, Will! (Will is well your first name?).

Great job!

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

Let me to do a copy of this post in the "technical" part, to allow you to have your own topic, as Mr Payart has his own one.

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

Thank you Marc! Actually "Will" is my last name (surname). Riley is my first name.

No pressure transducers were ever used in our engine development.
And time/aerea was never calculated.
The port timings remained practically the same during 15 years!
What we did was trying different angles and radiuses, mainly on
the transfer ducts. I think we tried 40 different types of transfer ducts
that did not chanche the time/aerea. It was all about in which direction
the charge entered the cilinder and how the tranfer streams influenced upon
each other! Also about 200 different exhaust pipes were tried. After 2004
nothing much was changed but we improved with different power jet and
ignition mapping. It seemed nearly impossible to improve the transfer ducts
any more. The exhaust ducts were CNC machined, using different programs,
mainly to reduce exhaust duct volume. Also about 100 head designs were tried.
This work was done over a period of 12 years.
In september 2004 the design of the RSA started, at Derbi, and the first dyno
test was in october 2005. In the meantime Aprilia had been bought by Piaggio
which also owned Derbi, so we could use Aprilia cilinders.
The engine went very well almost at once!

Hello Riley,

I see you made a very nice single cilinder engine!
What HP do you achieve with a reed valve, using the same cilinder?
When working at Derbi a reed valve engine seemed far inferior!
But we did not use the same cilinder!

Jan Thiel a écrit:

No pressure transducers were ever used in our engine development.
And time/aerea was never calculated.
The port timings remained practically the same during 15 years!
What we did was trying different angles and radiuses, mainly on
the transfer ducts. I think we tried 40 different types of transfer ducts
that did not chanche the time/aerea. It was all about in which direction
the charge entered the cilinder and how the tranfer streams influenced upon
each other! Also about 200 different exhaust pipes were tried. After 2004
nothing much was changed but we improved with different power jet and
ignition mapping. It seemed nearly impossible to improve the transfer ducts
any more. The exhaust ducts were CNC machined, using different programs,
mainly to reduce exhaust duct volume. Also about 100 head designs were tried.
In september 2004 the design of the RSA started, at Derbi, and the first dyno
test was in october 2005. In the meantime Aprilia had been bought by Piaggio
which also owned Derbi, so we could use Aprilia cilinders.
The engine went very well almost at once!

Edit by Marc: Thank you very much to share your knowledge, Mr Jan Thiel.
I am so happy that i can't wait more before asking you a question (i will introduce myself in few secondes)...

You build 40 diffent Cylinder´s to test the different angels and radiuses?
Or is there any trick?

Waiting for you answer, i am going to buy a "savoir vivre" manual.
Thank you Mr Jan Thiel.
:)

Ah oui un Toopack énervé ça calme
Bon l'anglais n'est pas au top mais je pense que le p'tit nouveau aura compris...
J'espère qu'il va rester après un accueil pareil ; c'est le premier Allemand sur le forum je crois...

but the expression of Mark reflects my thought better that I writes it

i'm sorry JoeHännes !

Dear Mr. Thiel,
The 125cc engine made 48 hp (sae) at the rear wheel. I have used my cylinder on the Rotax 129 engine where it made 50hp. Much of our technology has been derived from Aprilia. I believe I can make more with the reed valve engine by focusing development on the reedcage and inlet. However, it has been my experience that the mid range power of the disk valve engine is always superior. I have found over rev power of the reed valve engine to sometimes be eassier to achieve. In the past I would also produce more peak hp with the reed valve engine but the mid range maybe 7% less than the disk valve. Our 150cc engine when using Methanol has made 56hp and 24 ftlbs of torque. I love it for its simplicity. Our 250cc twin has made 104hp when using leaded fuel and Aprilia MW47 combustion chambers. I have also made tests on a 125cc disk valve engine with fuel injection. This made 10% more power everywhere than carburated!!! I want to spend more time in this area. At the moment we are fine tuning our 250cc twin engine for the 2011 superkart season. We have made crankcase, cylinder, and combustion chamber modifications in order to raise peak HP and over rev HP. By reading this forum I found an area where I may have been wrong in my design, we are on the dyno friday to confirm.
Thank you for your input!
I would love to produce a twin cylinder tandem firing front disk valve engine for superkarting, maybe you would have some ideas on this?

Riley Will a écrit:

I would love to produce a twin cylinder tandem firing front disk valve engine for superkarting

There's a simple solution, Riley: turn your engine 90° anti-clockwise on the chassis, and you'll have it all: twin cylinder tandem AND front disks. You would have to use a prop shaft to the rear axle, though...

Joking apart: I can't see how you can have everything you wish for. And why would you want the engine to fire on both cylinders simultaneously? That is unnecessarily hard on the primary drive, the clutch, the gearbox, the chain and the rear tires.
I would not be surprised if Jan Thiel would propose something like this: the JBB engine. It is a lot lighter and more compact than a tandem twin. You would only have to mirror its design to get the carburettors at the outside. Or, MUCH better on a kart, use fuel injection (is that allowed?).
[Vous devez être inscrit et connecté pour voir cette image]

Mr. Overmars,

Yes, tandem firing is very hard on components, but the reward of traction on a superkart is worth it. Much like the 500cc V4 era and the introduction of "big bang". A superkart opens the throttle very early compared to a bike. At Laguna Seca we used 100% throttle 76% of the lap!!!

I built a twin engine kart, an engine on either side. When I used 180 degree firing the kart was like a drift machine. When I fired the engines together it was able to "hook-up" and launch between the turns with very little tire spinning.

This is the new twin engine sprint kart that is currently being built by us:
[Vous devez être inscrit et connecté pour voir cette image]

Does the JBB engine share a common crankcase and doubled up connecting rod on common crank pin?

@ Riley Will

On this picture I see a special carburator with two entries, could you tell me more ?
[img][Vous devez être inscrit et connecté pour voir cette image][/img]

Thanks.

Those are the carburators used when burning methanol. It is needed not for more air, but to have the ability to move enough methanol!!! When running with Methanol, you can see your fuel tank dropping on the straights!!!!

Riley Will a écrit:

Mr. Overmars,

Yes, tandem firing is very hard on components, but the reward of traction on a superkart is worth it. Much like the 500cc V4 era and the introduction of "big bang". A superkart opens the throttle very early compared to a bike. At Laguna Seca we used 100% throttle 76% of the lap!!!

I built a twin engine kart, an engine on either side. When I used 180 degree firing the kart was like a drift machine. When I fired the engines together it was able to "hook-up" and launch between the turns with very little tire spinning.

Does the JBB engine share a common crankcase and doubled up connecting rod on common crank pin?

I do appreciate the courtesy of you addressing me as Mr. Overmars, but please call me Frits; otherwise I will have to start looking for a necktie...
There is a lot of misconception about big bang. Maybe this will help: [Vous devez être inscrit et connecté pour voir ce lien] .

We too have been playing with a twin-engined kart for the last few years:

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

The JBB engine (created by Jean-Bertrand Bruneau who is a member of this forum), has two separate crankcases.
The crankshaft has a common big-end pin with a center disc which forms the separation. Hopefully the following pics will make it clear:
[Vous devez être inscrit et connecté pour voir cette image]

What crankshaft balance factor is the RSA using?

Which one? The RSA125 (single cylinder + balance shaft) or the RSA250 (two contra-rotating crankshafts)?

Riley Will a écrit:

Those are the carburators used when burning methanol. It is needed not for more air, but to have the ability to move enough methanol!!! When running with Methanol, you can see your fuel tank dropping on the straights!!!!

for Mr Riley
what kind of changes should be made to the exhaust with the use of methanol?
the increase in compression ratio that is between gasoline and methanol?

thank you very much
i am an Italian two stroke lover

Frits,

On the RSA 125cc, how much was the balance percentage was crankshaft and how much was balance shaft to make the 55%? Any idea about the 250's balance factor yet?

bic1983,

I have been told that a good gas exhaust will work well with methanol, but the reverse is not always true. I have never developed and exhaust for methanol so I cannot comment on the specific design changes, sorry.

Riley Will a écrit:

Frits,

On the RSA 125cc, how much was the balance percentage was crankshaft and how much was balance shaft to make the 55%? Any idea about the 250's balance factor yet?

bic1983,

I have been told that a good gas exhaust will work well with methanol, but the reverse is not always true. I have never developed and exhaust for methanol so I cannot comment on the specific design changes, sorry.

then.. use a standard expansion chamber on your methanol-fueled engines?

I was aware that the exhaust from an engine fueled with methanol,
are colder than a gasoline
so ... there's a different speed sonic wave in the expansion


thanks mr riley honored to exchange views with you

Salut à tous ,

Avez vous testé différentes longueurs de bielles (avec les carters-cylindres qui vont avec)?

Hello Guys,

Have you ever test the lengt variation of the conrod (with the crankcases-cylinder-transfers) on the bench?

This main part is always out of the specs , why?

If it is possible ,can you tell us more about internal pressure of principal ducts ?
With FTX tool (or a similar tool) where do you put the lambda ? in the last centimeter duct ? In the up side ?

With a flow bench what kind of proportion do you obtain in rsa cilinder ? I mean for example , if the principal port gives 42 liters/sec , what can the secondary is used to give ?

In the rsa cilinder , the last centimeter section is increasing in the principal port and reducing in the secondary ; is it because of his inclination ?and to give enough pressure ?

As FTX web site is explaining , all the modifications that we make is made as we were blind. The dyno gives an indication but do not give each time a clear answer . Perhaps F.O.S can tell us more :)

Last question (lots of questions like you I have always a lot of question):
can you tell us more about the rsa cranshaft ? its total wheight , its size etc ? I saw that Jan Thiel talked about a 22 mm pin but this is all.

thanks.

fab, it's TFX and not FTX