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

Nombre de messages : 10 Localisation : canada Date d'inscription : 14/07/2017

J’aurais une question pour Jan !
J’ai copié un texte que vous avez écrit dans la partie3 !

And also the exhaust was cleaned at the inside, removing the carbon deposit.
After this it took about a week for the same maximum power to return.
And you also needed a richer carburation, because with a clean exhaust pipe the engine had more tendency to detonate.
The teams that went to the races always cleaned their exhaust pipes on the saturday evening, before the race.
I tried to convince them not to do this, but nobody believed me!
To a lesser degree the same thing happened with the dampers.
Filling them with new glass fiber always gave less power and more detonation, for about 3-4 days

Est ce que vous connaissez la raison qui fait que le moteur a tendance a détoné avec un exaust propre ?
Merci
Patrice.

Nombre de messages : 4 Localisation : Portugal Date d'inscription : 14/01/2018

hello,

i am building a b/s 52x48 , what the best shape measures for the rotary valve ?
thanks

This one is not a 125cc lol!

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Nombre de messages : 4 Localisation : Portugal Date d'inscription : 14/01/2018

Someone have the measures of the rotary rsw crankases shape

I only remember that the rotary valve diameter was 126mm

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hello,
is it sensible to use carbon rotary discs on an aluminium surface without a steel plate? Will there be too much abrasion?

more abrasion will be on outer side, so you can easily replace it. but one two seasons it will be good

Nombre de messages : 10 Localisation : canada Date d'inscription : 14/07/2017

J’aurais une question pour Jan ou Fritz !
Quelle est la meilleur facon d’installé le cylindre sur un flowbench pour testé le port d’exaust ?
Premierement est ce que c’est mieux de poussé l’air dans le port ou de la tirré ?
Plus bas je vous copie un liens d’un vidéo que j’ai trouvé sur youtube !
Merci encore
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Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

Seulement tirer. Avec un Superflow ( machine ridicule ) la temperature devient plus haute.

Nombre de messages : 10 Localisation : canada Date d'inscription : 14/07/2017

M. Fritz Est ce que vous connaissez la pression que l'on devrait utilisé(flowbench) pour un port d'exaust ?
merci

porttiming124 a écrit:: M. Fritz Est ce que vous connaissez la pression que l'on devrait utilisé(flowbench) pour un port d'exaust ?

That depends on the capacity of your flow bench. The stronger pressure the better, although no flow bench in the world can approach the real pressures in a firing engine.
Most flow benches are operated at 40" water column (yes, they still use those antique imperial units of measure).
It also depends whether the flow bench uses a closed-loop circulation, with the disadvantage that the air becomes hotter and hotter, as Bob van der Zijden wrote above, or an open system which uses more energy and produces more noise.

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

Superflow works as far as I know with 20 inches of test pressure and uses th measuring flange principle which costs an awful lot of losses. The distance between this flange and the measuring port should be 1000mm This is impossible to make practically as it should be a straigt pipe.
The only smart way of measuring is with a careful calibrated hot film air mass meter, standard hardware in all cars. And NOT a hot wire system. Two main advantages of this system are the accuracy and the very high efficiency. In order to get a near perfect laminar flow fitting of honeycomb material over at least 200 mm in front of the air mass meter imakes the system perfect. I've built a couple of these machines until my German partner pulled out of the project. Shit happens.

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

Rectification: test pressure by Superflow is 28 inches.

Tada to all of you.

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

PS

Another smart feature of the hot film air mass meter is the fact that the measuring unit is air mass/weight and not the silly cubic feet per minute by the yacking fonks of Superflow and all its copying monkeys
what my fantastic teacher Bob Kampschuur at the Anthony Fokker School in Scheveningen/The Hague called apples per square meter open window. On top of this there is an integral NTC temp sensor and sometimes a non backflow feature.

Nombre de messages : 10 Localisation : canada Date d'inscription : 14/07/2017

Ok parfait je suis capable de faire des test a 40" water inch !

Sur un moteur 4 temps on fait les test de tète avec différent ouverture de la valve comme vous savez.

exemple .050 inch d'ouverture
.100 inch
.150 inch
etc.....

Avec tout les test que j'ai fait sur les tètes j'en suis venue a la conclusion que l'idéal est de faire les test a 87% de l'ouverture maximum de lift du cam !

Sur un 2 temps comment je doit procédé ?
Est ce que je suis mieux de fonctionné en degré de crank shaft ou en mm de courses?
merci Fritz

Nombre de messages : 10 Localisation : canada Date d'inscription : 14/07/2017

Bob van der Zijden a écrit:: PS

Another smart feature of the hot film air mass meter is the fact that the measuring unit is air mass/weight and not the silly cubic feet per minute by the yacking fonks of Superflow and all its copying monkeys
what my fantastic teacher Bob Kampschuur at the Anthony Fokker School in Scheveningen/The Hague called apples per square meter open window. On top of this there is an integral NTC temp sensor and sometimes a non backflow feature.

ok thank you
Bob

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

When testing a 4stroke head the flowbench tells you that for a given inlet valve diameter of 42mm there is hardly anymore flow above vave lift figures of around 11mm. But hard practice has learned us that a lift of 14mm does wonders in a good engine. This seems to be overseen too often. And apparently nobody mentions this. Cause of this shit is the the is pulsation phenomenon happening in an inlet port. Have a look at the Helmholz theory. I happen to
have a near perfect (sic!) rule of thumb for inlet tract lengths .

Bob van der Zijden a écrit:: When testing a 4stroke head the flowbench tells you that for a given inlet valve diameter of 42mm there is hardly anymore flow above vave lift figures of around 11mm. But hard practice has learned us that a lift of 14mm does wonders in a good engine. This seems to be overseen too often. And apparently nobody mentions this. Cause of this shit is the pulsation phenomenon happening in an inlet port. Have a look at the Helmholtz theory. I happen to have a near perfect (sic!) rule of thumb for inlet tract lengths .

Yep, if valve lift is one-quarter of the valve seat inner diameter, the open curtain area equals the duct area; lifting the valve any further does not improve the maximum flow. But lifting the valve higher will bring about this maximum flow condition sooner and maintain it for longer.

Bob, did you notice that I did not once mention the name Superflow? Food for thought, eh?

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

I do know that, but we should not forget that there is an awfullot of resistance in the inlet system. Therfore we have to calculate with the discharge coëfficiënt amongst others. In the old days we used low valve lift and long duration,due to the development in the late 70's in F3. John Judd used already 14mm lift with short durationwith a 40mm valve. A real problem for the valve springs. Dr Ing PETER KUHN, the brillant designer of Helut Fath's URS engine learned us with his Doctor Arbeit the new way for and how to make valve springs. Schmitthelm in Heidelberg produced them. As far as I know was Kuhn the initiator of the now common contact springs. For comparison:
In 2strokes there are 2 ways of inlet : large diameter inlet with short timing vs small inlet with longer duration.

Nombre de messages : 94 Localisation : Hollande Date d'inscription : 10/09/2013

By the way, Neil Williams founder of Superflow screwed me by not paying my fee for selling fe 901 dyno and a 600cfm flowbench to Skoda in Mlada Boleslav in around 1985. And that was not the only case. I do hope he will burn in hell, the bastard. Prick like Trump.

Salut je vous suis, et je vais survoller votre tread, qui a l'air d'etre exaustif.
et intéressant.
tzrcarbonn
Québec 30 01 2018 6.57 pm

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hi,

i´ve got one more question. It´s about the angle of the squish area.
The bore is 76,00mm. The curvature of the piston got a radius of 125mm.
Is a squish angle of 17° OK? Or is it better to give the squish area the radius of the piston + the measurement of the squish gap?
I thought of a cumbustion 1:12,5 with 100% Avgas.
I´m milling my own cylinder head for my Maico MD250 for a better cooling. I got all the measurements and volumes. The squish angle is the only thing i´m worried about.
@Frits: The Maico cylinder returned today from Laser-Welding. So i can file new port times in it.

Best regards,

Bernd

Döllinger a écrit:: i´ve got one more question. It´s about the angle of the squish area. The bore is 76,00mm. The curvature of the piston got a radius of 125mm. Is a squish angle of 17° OK? Or is it better to give the squish area the radius of the piston + the measurement of the squish gap? I thought of a cumbustion 1:12,5 with 100% Avgas. I´m milling my own cylinder head for my Maico MD250 for a better cooling. I got all the measurements and volumes. The squish angle is the only thing i´m worried about.

That piston shape astonishes me. 125 mm is a very small radius for a 76 mm diameter piston, giving a steep 17,7° edge angle, so a 17° squish angle is not OK, Bernd. It would enclose some fresh mixture at the edge, inviting detonation.
Besides, with that 17° squish angle the squish gap would open 0,4 mm towards the center. It you would choose an edge gap of 0,6 mm, the center gap would be no less than 1 mm, not desirable for effective squish.

It is always better to give the squish area the same radius as the piston. And you do not need to add the measurement of the squish gap to this radius, because under dynamic circumstances this gap will diminish.

Nombre de messages : 102 Localisation : Biblis Date d'inscription : 14/01/2017

Hi Frits,

thank you for your reply. I spoke to the manufacturer of the piston.(Kolben-Wahl) He said it is 125mm.
I made 2 photos and compared the piston to a drawn 125mm radius. You can´t see it that exactly, but i think it is possible to be the right measurement.
Here two photos of the piston.
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What you think about a gap of 0,8mm? I will choose the gap a little more narrow than that for the first time milling. So i can measure directly on the mounted engine and lathe to the right measurement after that. My possibilities don´t allow me to be that sure without endanger a 26kg alloy block.
Ok, i will get the same radius on the squish area. I think it won´t have a too big effect on my volume calulation.
Best regards,

Bernd

PS: I cut off a 125mm radius made of paper and compared it to the piston curvature. 125mm is correct!

Bernd, the three interlocked dimensions for the piston dome are:
dome radius 125 mm
edge angle 17,7°
height difference between edge and center 5,92 mm.
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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 5)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 4)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 2) (Locked)
» [GP125] All that you wanted to know on Aprilia RSA 125, and more, by Mr Jan Thiel and Mr Frits Overmars (PART 1) (Locked)
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