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

And again, for Jan, please, could it be a good method for a two-stroke, instead of choking the gas, to have electronic injection every 2,3,4.....revolutions of the crankshaft? Thank you

Architito2002 a écrit:

Frits Overmars a écrit:

melvyn trevor a écrit:

Frits, Many thanks for the prompt reply you have explained a lot for me, re-reading the post I can now see my confusion, would velocity be more appropriate, factoring in the driving pressure and exhaust diffuser action?Grateful thanks, Mel

Yes Melvyn, asking about the maximum velocity of gas flow makes more sense to me than asking about the maximum efficiency of the flow. The picture below shows a velocity profle of blowdown outflow. Note the effect of a radius at the top egde of the port. The maximum velocity at this point can be Mach 1. This will not be influenced by exhaust diffuser action, as the pressure differential during the onset of the blowdown phase is supercritical; lowering the downstream pressure will not raise the flow velocity any higher.
s[url=https://servimg.com/view/19520277/404][Vous devez être inscrit et connecté pour voir cette image][/url

Hello Frits, is this area likely to behave like a De Laval nozzle exceeding Mach 1? Thank you

That is what I am trying to approach with a raised exhaust floor, a radiused exhaust top edge and a radiused piston timing edge.
It will not become a real De Laval nozzle; that would require an exhaust floor moving up and down with the piston. But every little bit helps.

Architito2002 a écrit:

And again, for Jan, please, could it be a good method for a two-stroke, instead of choking the gas, to have electronic injection every 2,3,4.....revolutions of the crankshaft? Thank you

If you want low power cruising, skipping injection or ignition cycles may work.
If you want good throttle response, forget it.
Skipping just one combustion cycle means the exhaust resonance will stop and you will lose much more than just the power of that one missed cycle.
It may take up to 20 cycles before the engine has restored its full power after one skipped cycle.

By the way, that also happens each time you shift gear. The engine noise may return directly after a gear change, but the power does not.
The inertia of the crankshaft disguises the temporary power drop, but it would be far better to have a seamless transmission that does not need a torque interruption for each shift.
I drive a CVT vehicle  

Thank you Frits, always very kind and attentive. You have an exceptional vision of what happens in the two-stroke, you always manage to see all the possible facets. But therefore the wave swing dies so early. Indeed, in gear changes, in low-performing engines like the ones I've had the opportunity to play with, many times in gear changes you feel that the expansion no longer sounds even if you are in a rev range where it should do!!! Thanks Frits.
Another question, just to play, hoping you like it. An exhaust with two manifolds could work, one with a reduced section and great length and the other with a section adapted to the maximum power with a flap valve that moves on one or the other, modulating, which varies the resonant frequency of the system from low to high?

What cvt bike do you drive?

Have you developed it for use in the city? If it's a 50cc it will have at least 30hp!!! [Vous devez être inscrit et connecté pour voir cette image]

Architito2002 a écrit:

Thank you Frits, always very kind and attentive. You have an exceptional vision of what happens in the two-stroke, you always manage to see all the possible facets. But therefore the wave swing dies so early. Indeed, in gear changes, in low-performing engines like the ones I've had the opportunity to play with, many times in gear changes you feel that the expansion no longer sounds even if you are in a rev range where it should do!!! Thanks Frits.

Another question, just to play, hoping you like it. An exhaust with two manifolds could work, one with a reduced section and great length and the other with a section adapted to the maximum power with a flap valve that moves on one or the other, modulating, which varies the resonant frequency of the system from low to high?
What cvt bike do you drive? Have you developed it for use in the city? If it's a 50cc it will have at least 30hp!!! [Vous devez être inscrit et connecté pour voir cette image]

​Thanks for the flowers, Potito.
Personally I'd prefer a trombone exhaust system over a switchable exhaust system with one long and one short pipe, but a switchable system will also work, as has been proven several times, even on Solex mopeds. Below are the switchable manifold and its two power curves from my mate Björn Enke.
[Vous devez être inscrit et connecté pour voir cette image]

About the CVT vehicle I drive: the English expresssion drive' might give you a clue. If your means of transport has less less than three wheels, you ride it, for example a horse or a bike. If it has more than two wheels, you drive it. So yes, my CVT vehicle is a Suzuki Swift .

Compliments are the least I can do. Know that if you came to Turin for any reason, I would also be happy to have lunch with you..... I certainly will not try to conquer you  [Vous devez être inscrit et connecté pour voir cette image]
Thank you very much Frits, sorry but I use an Italian-English translator and in Italian the same verb is used for drive the car and ride the motorbike.
Wow, what a beautiful result. I believe there was an on/off rotary valve switch in between. With electronic management you could ride ( [Vous devez être inscrit et connecté pour voir cette image] ) the best of both curves. In both curves there is the usual hole at 2/3 of the maximum power that You have described several times which could be eliminated. My thought, which apparently isn't just mine, would only have the advantage of using the same belly and therefore a single expansion. Cool

Frits please, where can I see your system 24/7?

It's very interesting what I've read about it, but I haven't found any explanatory pictures.

I fantasize about an eco-friendly two-stroke system many times.

Architito2002 a écrit:

if you came to Turin for any reason, I would also be happy to have lunch with you..... I certainly will not try to conquer you

Mangiare in Italia is one of the great pleasures in my life. And please do try to conquer me. I try to share my knowledge with the intention that my friends will eventually become better at it than me. Then I can relax and sit in the sun with a glass in my hand, watching them getting their hands dirty .

Citation :

sorry but I use an Italian-English translator and in Italian the same verb is used for drive the car and ride the motorbike.

Lo so .  You're not the only one who isn't aware of this small difference. Just look at the rider names on the fairings of race bikes. 90% of non-English people describe themselves there as driver

Citation :

Frits please, where can I see your system 24/7? It's very interesting what I've read about it, but I haven't found any explanatory pictures.

My good friend Roland Holzner sent me some nice pics a while ago. On the kart engines he was working on, it was not allowed to use any electronics, so he had to use a cam on the crankshaft that opened and closed his reed doors. At high revs the inertia of the reed doors caused them to stay open permanently.
If you are free to use a servo motor, things become much simpler and you don't need to worry about the inertia of the reed doors, so you can use just one door, like in my sketch below.
[Vous devez être inscrit et connecté pour voir cette image]

Citation :

I fantasize about an eco-friendly two-stroke system many times.

]You would have to scavenge it with clean air, without any oil or fuel, like the giant marine diesels do. They use the dirtiest (and cheapest) sulphurous fuel there is, but with a fuel like ethanol they would be cleaner than any four-stroke.

.

Frits Overmars a écrit:

Architito2002 a écrit:

if you came to Turin for any reason, I would also be happy to have lunch with you..... I certainly will not try to conquer you

Mangiare in Italia is one of the great pleasures in my life. And please do try to conquer me. I try to share my knowledge with the intention that my friends will eventually become better at it than me. Then I can relax and sit in the sun with a glass in my hand, watching them getting their hands dirty   .

Citation :

sorry but I use an Italian-English translator and in Italian the same verb is used for drive the car and ride the motorbike.

Lo so .  You're not the only one who isn't aware of this small difference. Just look at the rider names on the fairings of race bikes. 90% of non-English people describe themselves there as driver

Citation :

Frits please, where can I see your system 24/7? It's very interesting what I've read about it, but I haven't found any explanatory pictures.

My good friend Roland Holzner sent me some nice pics a while ago. On the kart engines he was working on, it was not allowed to use any electronics, so he had to use a cam on the crankshaft that opened and closed his reed doors. At high revs the inertia of the reed doors caused them to stay open permanently.
If you are free to use a servo motor, things become much simpler and you don't need to worry about the inertia of the reed doors, so you can use just one door, like in my sketch below.

Citation :

I fantasize about an eco-friendly two-stroke system many times.

]You would have to scavenge it with clean air, without any oil or fuel, like the giant marine diesels do. They use the dirtiest (and cheapest) sulphurous fuel there is, but with a fuel like ethanol they would be cleaner than any four-stroke.

It would be an honor to have you as a guest and to be able to become your friend. But if it were to happen, don't ask me to become better than you, I wouldn't be able to.
I'm at a stage where I don't know whether or not to freely disclose what I have in mind that maybe doesn't even work.

Here's more than that you couldn't send me. So it is very clear and in the last image it is combined with your FOS system where you have addrized the tower of Pisa.  [Vous devez être inscrit et connecté pour voir cette image]
Great idea

As for the ecological two-stroke, it's exactly what I have in mind but I don't know if I will ever make it.
Yes, I've seen marine engines, too bad they don't have expansion!! :)
Yes, washing is done with volumetric compressors with a 4-stroke type base with very high yields.
In my idea washing is done with air too.
The crankcase pump is really used as such only to inject a rich mixture of air and petrol after the bmp or in any case with a very limited symmetrical transfer phase. Direct lubrication in the crankcase.

Hello good people of pitlane , my name is robert , I am from croatia , 27 years old and have been riding 2strokes since i was 4 years old, the first one being a Tomos a3 automatic , that was also the first one i rebuilt at age 12 , than basically never rode it again as i got a cr 80 as a present for my 12th birthday might of been 13th birthday il have to check . That was a beast at the time (to me) i still remember learning to operate the clutch, entering the powerband releasing the clutch too suddenly and the bike jumping up from under me and draging me trough th3 field for about 5 seconds, still have no odea how i managed to get the thing down without falling, managed to climb the bike and keep riding, and not stopping for good 5 minutes as i knew how to ride it , just not how to get going, so stopping was not something i was excited about:P but got a hang of it quickly, still don't know how that bike ran so long , basically with no maintenance except an air filter every now and then and a spark plug OFTEN , than i got a xr 600 at about 16 , well it was not being used by my uncle , and i was tall enough to ride it ,so i "stole it" from him (he let me ride it for 3 years) after that i didnt touch a 2 stroke until 3 years ago, and it was a scooter (i hated scooters with a passion as i got a mx bike very early in life and scooters were considered uncool by the people i considered cool at the time , bukers mostly) , aaand i loved the way the cvt acts with the 2 stroke engine , saw the potentially instantly after driving a early aerox with just a linear pulley

so i started watching youtube ,ported my first cilinder ,a dr.evo 70cc on a gilera runner , i seized it because i didnt start running premix , and the oil pump line broke . Leaving my engine with no oil , the cilinder was intact somehow. But the crank , piston,head were all junk, so i bought a top performance due+ secondhand , just to find out i have been scammed and it was not the dimension it was said to be (bore was already at the max it could go, no more rebores , and it was bad) . But as the luck would have it i bought the right wrong cilinder, as its the same as my kit was , just ported a little hotter, so i coppied the port timings over to my cilinder and boom, the thing went 120kph gps indicated , was the happiest at 11.5krpm but would overrun to 12.5k after it "ran out" of cvt... Aaand one day working on it , left it with the cilinder off , piston on , brothers son came over and cracked it over , smashing the piston to pieces. So i lost the will to work on it and sold it . Now i bought a gilera stalker with a polini sport kit a polini cvt ,full crank ,21mm phbg carb yasuni c16 exhaust etc...
I now want to port it properly (well as much as a single exhaust port ,cast iron, air cooled ,oversquare engine can be ported that is ) i have read alot on this forum , iland now i have an idea about how to port , what may or may not work etc , but yesterday after about the third time of opening the fos scavenging concept jpg i noticed the formula for the axial angle of the transfer ports ,amd i have no idea how to use it , i mean if i used it right its 1.16 for my boost port , if i turn that from radians to degrees i get 66 degrees . Am i doing it right or wrong ,?its 39.3mm stroke, 47.4mm bore .
Also it has 0.9mm squish with the stock gasket , but the ports are not fully exposed that way, ie when piston is in bdc it is still covering about 0.5-0.7mm of the transfer ports
Should raise it so the wholeT ransfer ports are exposed and have the jug lowerd by 0.9mm at the top, so i get the whole ports and i get 0.7 mm of squish?

BlackD3vil a écrit:

after about the third time of opening the fos scavenging concept jpg i noticed the formula for the axial angle of the transfer ports ,amd i have no idea how to use it , i mean if i used it right its 1.16 for my boost port , if i turn that from radians to degrees i get 66 degrees . Am i doing it right or wrong ,?its 39.3mm stroke, 47.4mm bor .

Hello BlackD3vil, welcome on Pit-Lane.
The axial angle of that port should be ATN(1,4* (stroke / bore)) which is ATN(1,16), so you got the 1,16 right.
But those 1,16 are not radians. Arctangent (1,16) = 49,25 degrees, and that should be your upward axial angle. But don't worry about the decimals.
You can find the definition and explanation of the Arctangent function here: [Vous devez être inscrit et connecté pour voir ce lien]

Citation :

Also it has 0.9mm squish with the stock gasket but the ports are not fully exposed that way, ie when piston is in bdc it is still covering about 0.5-0.7mm of the transfer ports. Should raise it so the whole Transfer ports are exposed and have the jug lowerd by 0.9mm at the top, so i get the whole ports and i get 0.7 mm of squish?

The first thing to do is to get your transfer timing right. If the transfer ports are not yet fully opened by then, so be it.
The next step is to get your squish gap right. If your engine is not very worn by now, you can go as tight as 0,4 mm.
When you mention the stock gasket, I assume you are talking about the cylinder base gasket. Well, no one is forcing you to use the stock gasket, so you may be able to play a little here.
I do not recommend removing material from the cylinder top face. It is irreversable and you may regret it later. I'd prefer to remove some material from the cylinder head (which is usually much cheaper than the cylinder) so that the head can center into the cylinder bore.

i dont know how to get the quotes right...
but its an apsolute honor and a privlage "talking" to you Mr. Frits

i wanted to make the head go into the cilinder but was afraid that it would cause detonations or that the fit betwean the head and cilinder might become too small as it heats up, and that that m,ight interfere somehow with the engine, that makes it much simpler, how big of a clerance do i need?

and if thats the cased, im thinking of reshaping the head so it gets the proportions of the rsa one

the engine has just been rebuilt, so it should be quite tight, il try it out over the week , thank you very much for the informations, curently ordering a contra angle dental tool so i can rly port the transfers well

Wow, it's been a long week reading ALL the pages of ALL the 5 parts of this discussion!
I'm italian mechanical engineer, Vespa and Moped (Monferraglia) driver. Only on the road, truly speaking i do not like racing cause i'm afraid of speed  [Vous devez être inscrit et connecté pour voir cette image]
but i'm curious and since i've done a lot of studies on the 2 stroke theories i'm always starving to understand more and more.
I've read many scientific papers and books (Gordon P. Blair, Graham Bell, Gordon Jennings)

i've take a note of some questions for @Jan Thiel and @Frits Overmars about some of their statements:

Frits:

There is a simple fixed relation between blowdown angle.area and inlet angle.area: both need to rise linearly with rpm.
Since they do not depend on rpm, how could they rise with rpm?


The total angle.area of the transfers divided by the total scavenged volume per cylinder (cubic capacity plus combustion volume) determines at which rpm the engine starts running out of breath. Revving it much higher does not make much sense.

Could you please explain this? on what i understood the Angle.area it is not depending on rpm, the same is the total scavenged volume. Previously you said that is a good idea keep the SpecificTimeArea (STA=time.area/tot vol and time.area=angle.area/rpm) equal to a reference value, for the transfer this value is 66.16°mm2 per cc per 1000rpm.



Frits+Jan:
-any tip (or rules of thumb) on the right diameter of the carburetor?

-Do you guys know Franco Tormena? He is known as one god of 2stroke here in italy, with a lot of tales regarding his performance but you both never mentioned him.

-Why in the RSA the exhaust duct is directed toward the base of the cylinder and not perpendicular to the cylinder axis?

-I've read and understood all the aspect regarding the piston pin offset but i miss the advantage to use it. It changes the TDC&BDC position, the distance and the angle from one to other but why i should do that once the crankshaft and the cylinder have already been designed?

Thanks

chiccopeso a écrit:

Wow, it's been a long week reading ALL the pages of ALL the 5 parts of this discussion!

Benvenuto Chiccopeso, When you've recovered from all that reading, I've got some more reading material for you:
[Vous devez être inscrit et connecté pour voir ce lien]

Citation :

Frits: There is a simple fixed relation between blowdown angle.area and inlet angle.area: both need to rise linearly with rpm.
Since they do not depend on rpm, how could they rise with rpm?

Existing angle.areas do not rise with rpm, but required angle.areas do, because blowdown, transfer end inlet each require certain amounts of time.area, and as the rpm rises, the time per crankshaft degree deminishes.

Citation :

The total angle.area of the transfers divided by the total scavenged volume per cylinder (cubic capacity plus combustion volume) determines at which rpm the engine starts running out of breath. Revving it much higher does not make much sense.. Could you please explain this? on what i understood the Angle.area it is not depending on rpm, the same is the total scavenged volume. Previously you said that is a good idea keep the SpecificTimeArea (STA=time.area/tot vol and time.area=angle.area/rpm) equal to a reference value, for the transfer this value is 66.16°mm2 per cc per 1000rpm.

You can find more comprehensive explanations in my FOS tips & concepts in the above link.

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Frits+Jan:any tip (or rules of thumb) on the right diameter of the carburetor?  

For a rotary valve engine try the square root of (cylinder capacity x rpm of maximum power) / 900.
For a reed valve engine try the square root of (cylinder capacity x rpm of maximum power) / 1100.

Citation :

Do you guys know Franco Tormena? He is known as one god of 2stroke here in italy, with a lot of tales regarding his performance but you both never mentioned him.

I have never come across this name. Maybe Jan has?

Citation :

Why in the RSA the exhaust duct is directed toward the base of the cylinder and not perpendicular to the cylinder axis?

Because it flows better that way; see the picture below (you will find that same picture in the FOS tips & concepts)..

Citation :

I've read and understood all the aspect regarding the piston pin offset but i miss the advantage to use it. It changes the TDC&BDC position, the distance and the angle from one to other but why i should do that once the crankshaft and the cylinder have already been designed?

You do not have to. The changes in TDC and BDC positions ar minuscule anyway; the only real influence is on the con rod angle.
Personally I prefer a simple piston without offset.
[Vous devez être inscrit et connecté pour voir cette image]

Thanks!
i've already seen your material [Vous devez être inscrit et connecté pour voir cette image]

Dear two-stroke community and dear Frits Overmars,
I am overwhelmed by what I find here.
I took part in German national championships myself between 1996 and 1998 on an Aprilia 125 RSW.
It was the 93 GP machine from “Team Aprilia Germany” / under team management Harald Eckl.

I became aware of the whole thing through YouTube "two stroke stuffing" and (now 56 years old) am reminiscing about old memories.

And yes, I still have the Aprilia.

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

I still remember that one of the main sponsors was quite upset that it had to be an Aprilia.
He asked me if I wanted to race or if I wanted to work....

At that time, it was extremely difficult to obtain information regarding the handling and tuning of a rotary valve two-stroke engine from Aprilia.
The few aprilia's used in the national championships disappeared very quickly because no one could get them running.
The switch from AVGAS to unleaded fuel was particularly difficult.

It took me a long time to get the calibration lists for my Dell Orto jet needles.
With the help of a physicist (I was still working in German aerospace at the time) I initially put together an Excell tool for carburetor tuning.

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

Later I also developed my own software with Visual Basic to change the gearbox setup quickly and accurately.

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

My Aprilia ran well and I only had one engine failure because I was a little too aggressive in choosing the ignition curve (ROTAX the black one) during a training session.
And now I find all the wonderful RSA and FOS DOS programs here on the Internet and I just can't believe it.
Fantastic!!!
Social media isn't really my thing but I'm excited to see what happens next.
Maybe I can contribute interesting details from this RSW era.

I still have connections to teams from the paddock from that time and i am currently making CNC engine parts for a friend who drives classic races with an Armstrong 256 ROTAX tandem.
So the matter hasn't completely left me.

I know... it's extremely unlikely... but Frits - there's always a coffee ready for you near Cologne ;-)

Oliver Oettel a écrit:

Dear two-stroke community and dear Frits Overmars,
I am overwhelmed by what I find here.
I took part in German national championships myself between 1996 and 1998 on an Aprilia 125 RSW.
At that time it was extremely difficult to obtain information regarding the handling and tuning of a rotary valve two-stroke engine from Aprilia.
With the help of a physicist (I was still working in German aerospace at the time) I initially put together an Excell tool for carburetor tuning.
Later I also developed my own software with Visual Basic to change the gearbox setup quickly and accurately.
And now I find all the wonderful RSA and FOS DOS programs here on the Internet and I just can't believe it.
Fantastic!!!
Social media isn't really my thing but I'm excited to see what happens next. Maybe I can contribute interesting details from this RSW era.
I know... it's extremely unlikely... but Frits - there's always a coffee ready for you near Cologne ;-)

Vielen Dank für die Blumen, Oliver, und für das Kaffeeangebot.
I am eagerly looking forward to anything you developed and to interesting details from your RSW period.

Dear two stroke community and dear Frits,
ik ben zeer vereerd door uw aanmoediging om hier iets bij te dragen.
(google translate ;-) ….. but my wife speaks Dutch (previous error:English  [Vous devez être inscrit et connecté pour voir cette image] ) quite well because she studied art in Maastricht [Vous devez être inscrit et connecté pour voir cette image]

Briefly my background - I come from the field of mechanical engineering and worked for 23 years in various departments in aerospace until I became self-employed in the field of materials physics in 2003.

Unfortunately, I have to temper your expectations a bit - unlike you (Frits), I was more on the “users” side and less on the side of “developers”.

I simply tried to use the resources available to me to put the complex handling of the RSW engine into a context I could understand.

Basically I had no idea what I was getting myself into and apart from a few races with reed valve engines I had no particular experience or training.
Other than my curiosity and perhaps the ability to put certain observations together into context, I have no special skills...

A good friend describes these characteristics very nice as “universal dilettantism”….

But I'll start anyway and hope to at least provide some entertainment.


I bought the Aprilia straight out of the pit lane from a team in October 1996, at the last round of the championship in Hockenheim. The team didn't do very well with the motorcycle and the results for the season were rather sobering.

I recently had another contact with the pilot at the time, who called the motorcycle a “dirty pig”.

The history of the machine was that it was used in 1993 under the driver Peter Öttl, as already mentioned in the Aprilia Germany team under the leadership of Harald Eckl.
The result of the championship was 10th place in the overall annual ranking.

In 1994-1995 the motorcycle was used by Alexander Folger (Xan) in races of the European and German Championships.
I have very good and detailed records of Xan from this time, but all based on CPS fuel.
Unfortunately, I couldn't find any information about where Xan ultimately ended up in the overall championship rankings. But I guess that he was always in the top ten.

Until October 1996, the machine was used by the team from which I finally purchased it.
They had a major engine failure (connecting rod rupture, partial penetrated into the gearbox) and it gave me a first impression of what I was getting into here.
In my home workshop I had the opportunity to get a first impression of the condition.

I purchased the motorcycle with an almost complete gearbox set (a few gears were unusable due to the connecting rod damage
) several combustion chambers and ROTAX cylinders of various configuration levels.
One that was "worked" with the engraving "Suter" (i think Eskil)
This was also the last one installed so I decided to more or less adopt the setup from the last Hockenheim race with the standard gearbox setup for a first test in Mugello.
By the way in my opinion one of the most beautiful race tracks in the world and ideal for rotary valve engines.

It was a DUCATI only event in Mugello late in the year, with Gilera Piumas and Ducati Supermonos also competing. The Supermonos were impressively fast…

In the paddock I was clearly the underdog and I received pitying comments and looks.
However, I estimate that very few people recognized what exactly was in my workshop tent.
I guess most of them saw a street Aprilia RS...

The next day at 8:30 it started.
10.4°C /998 atmospheric pressure, 93% humidity.
Unfortunately, I haven't been able to take the humidity into account yet.

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

Nothing relevant to be found in the records.…

In the records the nozzle 261 and the needle SK513 (K84), position 2 were used for various weather situations.

I placed it, always carefully!!!, in position 3, main jet 208.
You have to make decicions and to start with something….

It worked because I was coincidentally on the save side.

After a careful lap everything was checked and looked unremarkable.
II tentatively completed another 17 laps.

The lunch break came and the track was reopened at 2 p.m.

Now 17°C /998 atmospheric pressure, 58% humidity.

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

Carb setup as it was in the morning.
Result- I couldn't get out of the pit lane!?!

To shorten it...

I thought something must be broken and tried everything with the carb.
Main jet down, needle down ... ignition, rotary valve….etc.

Until around 5 p.m., in my final desperation, I used the nozzle 258 and was suddenly able to get back on the track!?!

Now I had an idea of ​​the path of suffering of the previous owner and suddenly I knew what my sponsor meant: “Hands off Aprilia’s”

There was a free race on Sunday. I had been testing all weekend and had no lap times.
So I agreed with the organizer on the last starting place.

Lots of DUCATI 888/851/Supermono/Gilera Piuma and one two stroke aprilia…. in the very last row.
Green light.....an extremely bad start procedure...

Finaly i caught the last Supermono at Correntaio  #12 but the guy from Switzerland caught me again just before the finish line
Second place and a lot of amazed participants later in my tent!?!

I met Horst Kassner at a later event in Hockenheim when he looked after Bernhard Absmeier.
He came past my tent and we started talking about the engines.
I described to him my observation-based, rather "esotheric" way of determining the carb tuning by reading the plug and piston.

He asked me if I knew about the Dell ’Orto lists.
Of course I didn't know what he was talking about. He looked at my needle set, disappeared and later arrived with copies of the matching lists for my needles.

It was as if a door to paradise had been opened for me...

These lists were the basis for my Excell mixture adjustment solution.
I later purchased my first APC cylinders from him along with the MW71 and 80 combustion chambers and the 98-R exhaust.
He also gave me the shape for the CFK rotary disk and instructed me not to remove the “said” edge in the outlet.  [Vous devez être inscrit et connecté pour voir cette image]

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

I think that this edge has to do with the phenomenon that the nice Norwegian came across in his YouTube channel "two stroke stuffing" when he held the wrench sideways into the exhaust and the system suddenly came into a different resonance.

I love his channel and his very similar way of approaching the problems.

So - I have a lot of documents from this time about the ROTAX / RSW engines. Sadly only in German. I also have a lot of the calibration lists and records as PDFs.
Does it make sense to put something like this in a file base or would there be problems with data protection/copyrights?

What i want to say with the long story is that without the help of a very friendly old fox it would have been very difficult for me to make progress. That's why I think it's great that both Jan and Frits are doing the honors here.
It is priceless!!!

Frits:  COCARB.EXE
Are the intermediate values ​​of the flow rate 30....40%....50%....- of the slide / needles positions interpolated or measured?

Oliver Oettel a écrit:

Frits:  COCARB.EXE. Are the intermediate values ​​of the flow rate 30....40%....50%....- of the slide / needles positions interpolated or measured?

My CARB, COBARB, NEEDLE and CONEEDLE programs use the needle dimensions as stated by the needle manufacturers.
Intermediate values between stated dimensions are interpolated.
I really enjoy reading stories like yours; keep 'm coming.
Of course racing a 250cc bike against competitors on 500s is unfair. But not in the way those competitors expected .
One more remark that struck me: "My wife speaks English quite well because she studied art in Maastricht".
I love that city, between Holland, Germany and the French-speaking part of Belgium.
But learning English there.... I think you could compare it to going to Köln if you wish to learn Dutch

Frits Overmars a écrit:

Frits Overmars a écrit:

Oliver Oettel a écrit:

Of course racing a 250cc bike against competitors on 500s is unfair.  

It is a 125cc RSW- not a 250

And SORRY..... dont tell her...
I corrected it "….. but my wife speaks Dutch quite well because she studied art in Maastricht "

Dear Frits,
Your software collection is such a useful pool of tools that it would be a shame if it wasn't transferred into the modern era due to the DOS basis.



But i can understand that you have better things to do then reprogram everything.

I have tested most of it and on my opinion some of them at least run on MS operating systems that are based on 32 bit.
Even on Windows 7, 32bit.
Problems arise as soon as some programs want to go to full screen.
It works up to Win2000 without any problems

Of course, I can't say what it looks like in detail, for example when communicating with interfaces ("Windoof" (ich hoffe Du verstehst diesen deutschen Ausdruck  [Vous devez être inscrit et connecté pour voir cette image] ) always likes to hack in between....)

My own experience has been that all programs that are written with Visual Basic, for example, can also be run on 64bit WIN7/WIN 10 etc.

Due to the fact that I've had a "trauma" with the carburettor tuning since the pit lane desaster Mugello 96  [Vous devez être inscrit et connecté pour voir cette image]  and you've already provided the JET.EXE algorithm, wich makes it quiet more easy, i will start that as my first little project.
So i have a few questions about it.

In contrast to me, your JET.EXE program also takes the relative humidity into account. Even if it is the icing on the cake, it is still very interesting to check my old records with your program to see whether the carburettor should have been equipped a little differently back then.

    1. Due to the fact that I like to comment on the code clearly, I would like to know what the designations are for C0/C1/C2/C3 ?

I already have a first rough version running on VB.

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

In my Excel tool I corrected all the values for the flow rates according to percent slide position with the factor based on a past carburettor tuning, which resulted in an optimal racing result and good engine characteristics.

From this data, the values are corrected/interpolated using the factor depending on the weather data.
In my case it was the K84 needle. Of course, every new calculation is always based on this needle profile.

    2. How did you define when a different needle profile became necessary? Exhaust gas measurements?

Please be gentle with me if from here may i write/ask complete nonsense,.....

So  as an example the needle system lets through 208ml/min at 100% slide opening, there is no point in using a 210 main jet, which I wouldn't have found out without the Dell Orto lists.
"Theoretically" you could drive it without main jet's.

    3. Was there also a standard factor for the main jet, for example factor 0.976 multiplied by the maximum flow rate of the needle system ?

The water content in the intake air does not appear to have a serious influence on the mixture composition.

    4. Only for understanding..... What does a high proportion of water in the intake air do?
More like cooling because it takes a lot of energy away from combustion? Could there be at least partial pyrolysis? Is some kind of steam engine effect conceivable?

There are a few CNC programs included. Would you like to say someting about this?
I myself have older but good CNC milling machines from the 90s in my workshop and have looked at the programs in an editor.
They appear to be created in CAM because they are all in G1 commands.
A few programs seem to be for ducts.

Thank you, cheers and have a nice weekend

Oliver

Oliver Oettel a écrit:

Dear Frits, your software collection is such a useful pool of tools that it would be a shame if it wasn't transferred into the modern era due to the DOS basis. But i can understand that you have better things to do then reprogram everything.

We thought so too.
So now I'm designing an engine for a friend while he teaches my programs how to behave in the presence of 21st century operating systems.

Citation :

In contrast to me, your JET.EXE program also takes the relative humidity into account...  I would like to know what the designations are for C0/C1/C2/C3 ?

Those are the constants for approximating a vapor pressure curve.

Citation :

How did you define when a different needle profile became necessary? Exhaust gas measurements?

Not really. The aim is to create a linear relationship between throttle position and propulsion force, so you need a circuit and a rider who can accurately sense and communicate what is happening and what he would like.

Citation :

Was there also a standard factor for the main jet, for example factor 0.976 multiplied by the maximum flow rate of the needle system ?

No.

Citation :

The water content in the intake air does not appear to have a serious influence on the mixture composition... What does a high proportion of water in the intake air do? More like cooling because it takes a lot of energy away from combustion? Could there be at least partial pyrolysis? Is some kind of steam engine effect conceivable?

You can neglect relative humidity at low temperatures. It only starts to play a role above 20°C.
Water can absorb an astonishing amount of heat in its transition from the liquid to the gaseous phase. That heat is extracted from the other gases in the combustion chamber, so they cool down, which helps against detonation.
The water itself turns into steam and the steam pressure tries to turn your combustion engine into a steam engine. But because of the cooling, the pressure of the other gases in the combustion chamber drops, so the total pressure may go either way.

What does a high proportion of water in the intake air do?
Let's do some simple physics and assume an air pressure of the standard 1013 mbar, a temperature of 100°C and a relative humidity of 100%
At 100°C the vapor pressure of water happens to be 1013 mbar as well, and in this case 100% relative humidity means 100% absolute humidity!
There is no room for anything else any more: not even for one single molecule of oxygen.
You will understand what this means for combustion: it's not going to happen, and engine power will be zero.
By the way, this is also my litmus test for air density correction apps. Enter 1013 mbar, 100°C and 100% relative humidity, and the result should be an infinitely large correction factor. Most of those apps fail such a test...

Citation :

There are a few CNC programs included. Would you like to say someting about this?

Would I like to? Yes. Have I got time for it? No, because at the moment  am working with these programs ten hours a day.

Citation :

A few programs seem to be for ducts.

Yep

The poor pensioners have no time, they have to work 10 hours a day

Frank S. a écrit:

The poor pensioners have no time, they have to work 10 hours a day

Two errors in one sentence, quite an achievement Frank    .
A: I do not have to work, I do it because I still enjoy trying new ideas.
B: Yes, at the moment I work ten hours a day with the CNC programs. But those are not the only programs I am using every day   .

... just kidding Frits. Doing 2T-stuff isn't really work.