AccueilGalerieRechercherDernières imagesS'enregistrerConnexionNouveaux messages depuis dernière visite
Rechercher
 
 

Résultats par :
 
Rechercher Recherche avancée
Qui est en ligne ?
Il y a en tout 39 utilisateurs en ligne :: 7 Enregistrés, 0 Invisible et 32 Invités :: 1 Moteur de recherche

Gali, grand trophy, marco91, oliv, orion56, Stephane, VMAX

Le record du nombre d'utilisateurs en ligne est de 588 le Jeu 26 Sep - 4:33
Derniers sujets
» [Interview] Guy Coulon
250cc Air box design Icon_minitimeAujourd'hui à 11:55 par VMAX

»  [oldies] BOURG en BRESSE 1972
250cc Air box design Icon_minitimeAujourd'hui à 8:26 par philwood

» Honda V3 en préparation
250cc Air box design Icon_minitimeAujourd'hui à 8:14 par Dan42

» Malheureusement ils sont partis... et ils n'avaient rien à voir avec la moto
250cc Air box design Icon_minitimeHier à 20:16 par Joel Enndewell 2424

» Bourg en Bresse 1964
250cc Air box design Icon_minitimeHier à 16:48 par DidierF

» [Technique] La petite histoire du Desmo
250cc Air box design Icon_minitimeHier à 13:20 par Charly

» [Oldies] Questions (vitesse 1947-1976) (2)
250cc Air box design Icon_minitimeHier à 11:46 par DidierF

» [Oldies] Casques Premier 1974
250cc Air box design Icon_minitimeHier à 8:50 par philippe7

»  [WSBK] Infos 2025 .
250cc Air box design Icon_minitimeHier à 7:54 par les marluches

» [Oldies] Quizz (30)
250cc Air box design Icon_minitimeMer 6 Nov - 15:57 par jeannin

» Der de der Barcelone....
250cc Air box design Icon_minitimeMer 6 Nov - 14:46 par Aragon

» [Oldies] 80cc de vitesse : Toute leur histoire !
250cc Air box design Icon_minitimeMer 6 Nov - 14:13 par Nonoche

» [Oldies] Des livres sur la course moto
250cc Air box design Icon_minitimeMer 6 Nov - 13:19 par dga

» [oldies] GP Autriche Salzburg 1974
250cc Air box design Icon_minitimeMar 5 Nov - 19:38 par DidierF

» [Oldies] Barry Sheene, trajectoire d'une star
250cc Air box design Icon_minitimeMar 5 Nov - 15:45 par philippe7

» [Oldies] Jack Findlay, pilote de légende
250cc Air box design Icon_minitimeMar 5 Nov - 12:29 par jack177071

» [Technique] Réglage Keihin PWK28 sur 2t de trial
250cc Air box design Icon_minitimeMar 5 Nov - 9:24 par Troli

» Intempéries Valencia.
250cc Air box design Icon_minitimeMar 5 Nov - 7:55 par Aragon

» Bretagne Moto Classic 2024
250cc Air box design Icon_minitimeMar 5 Nov - 4:52 par diablo262

»  [MotoGP] GP 2024 de Malaisie à Sépang - Les 1 , 2 et 3 Nov 2024 .
250cc Air box design Icon_minitimeLun 4 Nov - 22:12 par Charly

» PROGRAMMES MANQUANTS - PGPM
250cc Air box design Icon_minitimeLun 4 Nov - 19:09 par sidthouv

» [Oldies] Les Koehler Escoffier
250cc Air box design Icon_minitimeLun 4 Nov - 18:01 par jeannin

» TT 1979:le dernier pour Mike Hailwood.
250cc Air box design Icon_minitimeLun 4 Nov - 11:51 par jack177071

» [Oldies] Questions (vitesse 1947-1976)
250cc Air box design Icon_minitimeLun 4 Nov - 11:46 par DidierF

» epoquauto 2024
250cc Air box design Icon_minitimeDim 3 Nov - 19:40 par cateralp

» [Oldies] Side-Car: quelques images
250cc Air box design Icon_minitimeDim 3 Nov - 19:01 par Fanchiom

» [Oldies] Aux origines...
250cc Air box design Icon_minitimeDim 3 Nov - 17:35 par Apriliabarth

» Bourg en Bresse 1958
250cc Air box design Icon_minitimeSam 2 Nov - 21:34 par DidierF

»  [MotoGP] Infos , nouveautés , potins , tests et plus pour la saison GP 2025 ...
250cc Air box design Icon_minitimeSam 2 Nov - 14:31 par EDOUARD Jean

» [2Stroke] Les MZ & Mr Walter Kaaden
250cc Air box design Icon_minitimeSam 2 Nov - 9:42 par jack177071

Mots-clés
charade bresse wanted fior moto motos 2013 rouge yamaha inventaire aprilia classic suzuki ducati 1976 1973 side oldies bourg coupe artisanales zone ROAD francaises Mans RACING
Meilleurs posteurs
Marc
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
EDOUARD Jean
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
philwood
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
Pierre"PhilRead"
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
mickey
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
yves kerlo
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
bubu
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
Fügner
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
Dialmax
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
Dan42
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
La réclame...
-10%
Le deal à ne pas rater :
-30€ sur la nouvelle Tablette tactile Lenovo Tab Plus – 11.5” ...
269.99 € 299.99 €
Voir le deal

 

 250cc Air box design

Aller en bas 
5 participants
AuteurMessage
Merlin7




Nombre de messages : 6
Localisation : uk
Date d'inscription : 06/03/2021

250cc Air box design Empty
MessageSujet: 250cc Air box design   250cc Air box design Icon_minitimeSam 6 Mar - 23:20

Hello all
I am in England I apologise I do not speak French, but I hope to get some advice.
We race a 250cc twin cylinder 2 stroke road race bike.
I would like to improve the air box by making it larger, at present it is about 5 lts volume.
I can make it larger but I'm wondering is there a good volume to aim for.
Also pressurised or still which is best.
If there are any discussion on air box design could someone point me in the right direction.
Many thanks

Len
Revenir en haut Aller en bas
crigar

crigar


Nombre de messages : 2248
Age : 67
Localisation : Ruoms 07 Ardèche
Date d'inscription : 14/02/2013

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeDim 7 Mar - 6:46

Bonjour,

D'abord c'est pour une utilisation "route" ou "circuit" ?

la boîte à air doit faire entre 10 et 20 fois la cylindrée totale soit 250 cc x 10 = 2,5 litres minimum mais mieux 250 cc x 20 = 5 litres

La pressuriser c'est pour le circuit mais les réglages (par exemple diamètre de l'entrée d'air, longueur du manchon, taille des gicleurs, de l'aiguille, du puits d'aiguille, etc) sont difficiles à trouver et souvent cause de serrage.

Voilà ce que je peux dire pour la base de travail. Mais tu ne nous explique pas quelle est ta machine, quel est l'usage que tu veux en faire, quelle est sa préparation (pot d'échappement, squish, etc). Avec ces éléments quelques personnes ici comme Frits Overmars ou Francis Payart pourront être d'un avis éclairé mais à distance sans voir la moto c'est très difficile car il y a beaucoup de paramètres à prendre en compte.
Revenir en haut Aller en bas
Frits Overmars

Frits Overmars


Nombre de messages : 2637
Age : 76
Localisation : Raalte, Holland
Date d'inscription : 12/10/2010

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeDim 7 Mar - 7:13

Merlin7 a écrit:
Hello all
I am in England I apologise I do not speak French, but I hope to get some advice.
We race a 250cc twin cylinder 2 stroke road race bike.
I would like to improve the air box by making it larger, at present it is about 5 lts volume.
I can make it larger but I'm wondering is there a good volume to aim for.
Also pressurised or still which is best.
If there are any discussion on air box design could someone point me in the right direction.
Many thanks
Len
Hello Len, maybe the text below is helpful to you.
================================================================
Tuning an airbox is anything but simple. It is not just a basic Helmholtz resonator with one volume and one supply duct because there is a second set of ducts (the carburetors), opening and closing with a varying frequency (the crankshaft rpm).

Speaking of volumes, simultaneously-firing multicylinder engines, for example tandem-twins and the Aprilia V-twin racing engines, have the disadvantage that both cylinders breathe at the same time, which causes large pressure fluctuations in the airbox. This should be counteracted with a large-volume airbox.

An airbox has two advantages: it ensures that the engine does not have to inhale air that has been preheated by the radiator, and at high riding speeds it provides ram air pressure. In the Aprilia RSA250 this extra pressure was 30 mbar at 260 kmh, good for 3% extra power.
But this extra pressure can also cause major carburetion problems. 30 mbar corresponds to a petrol column of about 400 mm height. And what is the height difference between the petrol level in the tank and the petrol level in the float chamber??
Under unfavorable conditions, this 30 mbar ram air pressure pushes petrol back from the carburetor to the tank, resulting in a lean mixture and seizures. So you need to ensure that the pressure in the fuel tank is always at least equal to the pressure in the airbox.

With an old-fashioned tank breather, it was simple: if 1 cc of petrol is consumed from the tank, 1 cc of air must be supplied at the same time to prevent depression in the tank.

But with an airbox you don't want to keep the air pressure in the tank equal to the atmospheric pressure, but you want to keep it equal to the airbox pressure. And if, for example, that pressure rises 3%, then 3% more air must be capable of flowing into the petrol tank within the same time.
With an almost empty tank, that is a considerable volume of air that must be supplied in a short time, requiring an internal air hose diameter of maybe Ø 12 mm.

The aeration nipples located on a carburetor on the left and right sides above the float chamber are normally connected to an overflow bottle. But if you use an airbox, you must ensure that the pressure in those aeration hoses is always equal to the pressure in the airbox.
The simplest way is to simply encase the whole carburetor(s) in the airbox, omit those aeration hoses altogether and connect the lowest point of the airbox to the overflow bottle. That only requires a small-diameter hose.

For the sake of safety, the Aprilia racers used an electric petrol pump. Then you no longer have to worry about the pressure difference between tank and airbox. But then you have to somehow make sure that when the battery runs out, the ignition stops sparking before the petrol pump stops pumping, otherwise things can become expensive ...
Frits Overmars
Revenir en haut Aller en bas
crigar

crigar


Nombre de messages : 2248
Age : 67
Localisation : Ruoms 07 Ardèche
Date d'inscription : 14/02/2013

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeDim 7 Mar - 8:00

Frits, ces explications sont uniquement pour les boites à air étanches ou bien pour toutes les boites à air ?

Frits, these explanations are only for airtight air boxes or for all air boxes ? (traduction by google Embarassed)
Revenir en haut Aller en bas
Frits Overmars

Frits Overmars


Nombre de messages : 2637
Age : 76
Localisation : Raalte, Holland
Date d'inscription : 12/10/2010

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeDim 7 Mar - 8:17

crigar a écrit:
Frits, ces explications sont uniquement pour les boites à air étanches ou bien pour toutes les boites à air ?
Frits, these explanations are only for airtight air boxes or for all air boxes ?
It depends on the amount of pressure rise due to riding speed. Obviously, if the airbox is completely open for the air to escape, there will be no ram air pressure rise. But otherwise, even if an airbox is not completely airtight, there may still be some pressure rise, so the safe way would be to treat every airbox as if it were airtight.
Revenir en haut Aller en bas
crigar

crigar


Nombre de messages : 2248
Age : 67
Localisation : Ruoms 07 Ardèche
Date d'inscription : 14/02/2013

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeDim 7 Mar - 8:35

Thank you !
Revenir en haut Aller en bas
Merlin7




Nombre de messages : 6
Localisation : uk
Date d'inscription : 06/03/2021

250cc Air box design Empty
MessageSujet: Air box design   250cc Air box design Icon_minitimeDim 7 Mar - 23:27

Frits Overmars a écrit:
crigar a écrit:
Frits, ces explications sont uniquement pour les boites à air étanches ou bien pour toutes les boites à air ?
Frits, these explanations are only for airtight air boxes or for all air boxes ?
It depends on the amount of pressure rise due to riding speed. Obviously, if the airbox is completely open for the air to escape, there will be no ram air pressure rise. But otherwise, even if an airbox is not completely airtight, there may still be some pressure rise, so the safe way would be to treat every airbox as if it were airtight.

Frith, thank you for the info.
Okay so I'm using an air box on my 250cc twin cylinder, is there a volume to aim for or just as big as I can fit in?
Revenir en haut Aller en bas
Frits Overmars

Frits Overmars


Nombre de messages : 2637
Age : 76
Localisation : Raalte, Holland
Date d'inscription : 12/10/2010

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeLun 8 Mar - 8:17

Merlin7 a écrit:
Frits Overmars a écrit:
crigar a écrit:
Frits, ces explications sont uniquement pour les boites à air étanches ou bien pour toutes les boites à air ?
Frits, these explanations are only for airtight air boxes or for all air boxes ?
It depends on the amount of pressure rise due to riding speed. Obviously, if the airbox is completely open for the air to escape, there will be no ram air pressure rise. But otherwise, even if an airbox is not completely airtight, there may still be some pressure rise, so the safe way would be to treat every airbox as if it were airtight.

Frith,  thank you for the info.
Okay so I'm using an air box on my 250cc  twin cylinder, is there a volume to aim for or just as big as I can fit in?
BIG
Revenir en haut Aller en bas
fpayart

fpayart


Nombre de messages : 1251
Age : 75
Localisation : LYON
Date d'inscription : 11/01/2010

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeLun 8 Mar - 13:16

Hi,

As big as possible.
Can you specify what is your type of engine.
Twin cylinder, OK but which configuration?
Twin parallel ?
Twin tandem ?
180 ° or 360 ° ignition cycle
What is your motorbike?

It is interesting to model your air box and its supply duct then, if possible, to make a flow simulation with CFD software.
Check the different flows and flow rates as well as the overall pressure drop.
Modify internal geometry and start over and over again ...

Read more here:
[Vous devez être inscrit et connecté pour voir ce lien]

Francis.
Revenir en haut Aller en bas
http://www.fperacing.com/
Merlin7




Nombre de messages : 6
Localisation : uk
Date d'inscription : 06/03/2021

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeLun 8 Mar - 23:24

[quote="Frits Overmars"][quote="Merlin7"]
Frits Overmars a écrit:
crigar a écrit:
Frits, ces explications sont uniquement pour les boites à air étanches ou bien pour toutes les boites à air ?
Frits, these explanations are only for airtight air boxes or for all air boxes ?
It depends on the amount of pressure rise due to riding speed. Obviously, if the airbox is completely open for the air to escape, there will be no ram air pressure rise. But otherwise, even if an airbox is not completely airtight, there may still be some pressure rise, so the safe way would be to treat every airbox as if it were airtight.

Frits my apologies, I didn't check my spelling before posting my reply.
So by BIG I presume the biggest I can fit in.
From you're earlier reply, altho it's not a fully sealed airbox I will try to place carbs fully inside the airbox Inc float bowl breathers. And if I understand correctly I need to run a pipe from airbox to fuel tank to maintain equal pressure in both tank and airbox.
Many thanks.
Len.
Revenir en haut Aller en bas
Merlin7




Nombre de messages : 6
Localisation : uk
Date d'inscription : 06/03/2021

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeLun 8 Mar - 23:29

fpayart a écrit:
Hi,

As big as possible.
Can you specify what is your type of engine.
Twin cylinder, OK but which configuration?
Twin parallel ?
Twin tandem ?
180 ° or 360 ° ignition cycle
What is your motorbike?

It is interesting to model your air box and its supply duct then, if possible, to make a flow simulation with CFD software.
Check the different flows and flow rates as well as the overall pressure drop.
Modify internal geometry and start over and over again ...

Read more here:
[Vous devez être inscrit et connecté pour voir ce lien]

Francis.

Yamaha tzr250 2ma,
parallel twin
180
Crank case reed valve
Revenir en haut Aller en bas
Merlin7




Nombre de messages : 6
Localisation : uk
Date d'inscription : 06/03/2021

250cc Air box design Empty
MessageSujet: FOS   250cc Air box design Icon_minitimeMer 10 Mar - 23:47

Dear Frits, I am interested to try you're exhaust design programme.
Is there a step by step explanation of this, as some of the terms I do not understand.
I appologise for asking, but I'd rather get instruction from the man who designed it rather than of some other website.
Thank you.
Revenir en haut Aller en bas
Frits Overmars

Frits Overmars


Nombre de messages : 2637
Age : 76
Localisation : Raalte, Holland
Date d'inscription : 12/10/2010

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeJeu 11 Mar - 8:37

Merlin7 a écrit:
Dear Frits,  I am interested to try you're exhaust design programme.
Is there a step by step explanation of this, as some of the terms I do not understand.
I appologise for asking, but I'd rather get instruction from the man who designed it rather than of some other website.
Thank you.
Len, I assume you are referring to my FOS Exhaust Concept. I tried to make it so simple that anybody could use it without help.
The drawing below should be self-explaining; all you need to do is to enter the values marked in yellow.
Which are the terms that you do not understand? Maybe with your help I can make the concept even more user-friendly.[Vous devez être inscrit et connecté pour voir cette image]
Revenir en haut Aller en bas
Merlin7




Nombre de messages : 6
Localisation : uk
Date d'inscription : 06/03/2021

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeJeu 11 Mar - 22:28

Thank you very much for the reply Frits, I shall have a go this weekend and report back to you if that's okay.
Revenir en haut Aller en bas
JanBros




Nombre de messages : 362
Localisation : Belgique
Date d'inscription : 05/12/2011

250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitimeVen 12 Mar - 22:03

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

Frits' concept he just posted in an excel, in which you can include a "Wobble exhaust duct"
Revenir en haut Aller en bas
Contenu sponsorisé





250cc Air box design Empty
MessageSujet: Re: 250cc Air box design   250cc Air box design Icon_minitime

Revenir en haut Aller en bas
 
250cc Air box design
Revenir en haut 
Page 1 sur 1
 Sujets similaires
-
» [Oldies] Honda 6
» european-2strokecup 250cc et 125cc 2012
» [Oldies] Kawasaki X-09 250cc
» [250cc] La 250 encore vivante
» [250cc] Championnat Italien GP250

Permission de ce forum:Vous ne pouvez pas répondre aux sujets dans ce forum
 :: ACTUALITES :: [GP] :: [GP125 (et 250 Snif!)]-
Sauter vers: