AccueilGalerieRechercherS'enregistrerConnexionNouveaux messages depuis dernière visite
Rechercher
 
 

Résultats par :
 
Rechercher Recherche avancée
Qui est en ligne ?
Il y a en tout 64 utilisateurs en ligne :: 11 Enregistrés, 0 Invisible et 53 Invités :: 3 Moteurs de recherche

Alain Gwada, cenvin, doum, ivan 2, Jean-Claude JACQ, jeannin, marco91, Monomil, PETIGA, Philippe Beziere, woab

Le record du nombre d'utilisateurs en ligne est de 294 le Lun 18 Nov 2019 - 19:11
Derniers sujets
» Alain Michel
250cc Air box design Icon_minitimeAujourd'hui à 20:06 par sylvainsolex

» [Oldies] Quizz (24)
250cc Air box design Icon_minitimeAujourd'hui à 19:45 par jrd

» L'électronique, opium du cancre...
250cc Air box design Icon_minitimeAujourd'hui à 19:35 par Toop

» Nogaro ce week-end ?
250cc Air box design Icon_minitimeAujourd'hui à 19:31 par cat

» extracteur inversé pour vis foiré
250cc Air box design Icon_minitimeAujourd'hui à 19:17 par crigar

»  [GP] GP du Portugal 2021 sur le circuit de Portimao les 16 - 17 et 18 Avril 2021
250cc Air box design Icon_minitimeAujourd'hui à 16:00 par Charly

» [Oldies] Les monos 4 temps Morini sauce bolognaise
250cc Air box design Icon_minitimeAujourd'hui à 9:07 par momodedale

» [Oldies] Restauration de mon side-car des années 70, la suite!
250cc Air box design Icon_minitimeAujourd'hui à 8:41 par Joel Enndewell 2424

» [GP] Guy Coulon
250cc Air box design Icon_minitimeAujourd'hui à 7:14 par Dan42

» [oldies] Adler, beaux 2 temps...
250cc Air box design Icon_minitimeAujourd'hui à 5:02 par Adco

» [Oldies] MV Agusta : l'histoire des motos d'usine en images...
250cc Air box design Icon_minitimeAujourd'hui à 0:55 par DidierF

» [Oldies] 1980 à 1988: Le Tour de France side-car, par Joël Enndewell
250cc Air box design Icon_minitimeHier à 6:02 par Joel Enndewell 2424

» [Oldies] Les casques de nos champions
250cc Air box design Icon_minitimeLun 19 Avr 2021 - 18:49 par zilo

» [WSBK] 2021
250cc Air box design Icon_minitimeLun 19 Avr 2021 - 9:56 par EDOUARD Jean

» [Oldies] Jarno Saarinen, la star qui a revolutionné le pilotage (Part 5)
250cc Air box design Icon_minitimeLun 19 Avr 2021 - 9:29 par daniel63

» [Pit Laners en course!] Clément Révolte (coupe YAMAHA R125)
250cc Air box design Icon_minitimeLun 19 Avr 2021 - 9:12 par EDOUARD Jean

» [GP] MotoGP et télévision...
250cc Air box design Icon_minitimeLun 19 Avr 2021 - 6:46 par Jean-Luc Morchio

» [Oldies] Collection motos en vente
250cc Air box design Icon_minitimeLun 19 Avr 2021 - 4:28 par alain83

» [GP] Johann Zarco
250cc Air box design Icon_minitimeSam 17 Avr 2021 - 12:29 par supermono

» Roulage amical à Belmont sur Rance
250cc Air box design Icon_minitimeSam 17 Avr 2021 - 10:51 par Jean-Rene

» [Moto2] NARD Ultra 6
250cc Air box design Icon_minitimeVen 16 Avr 2021 - 14:33 par Frits Overmars

» [Oldies] Barry Sheene, trajectoire d'une star
250cc Air box design Icon_minitimeVen 16 Avr 2021 - 12:24 par bubu

» Nard Ultra Y1
250cc Air box design Icon_minitimeJeu 15 Avr 2021 - 19:24 par Frits Overmars

» [oldies]Course de cote de la Foret Auvray dans l'Orne 61
250cc Air box design Icon_minitimeJeu 15 Avr 2021 - 14:29 par francois gomis

» [SORTIES] Montée historique auto-moto-side car de Pourville 20 juin 2021
250cc Air box design Icon_minitimeMar 13 Avr 2021 - 17:55 par Joel Enndewell 2424

» T.A.G (téchnique d'avant guerre)
250cc Air box design Icon_minitimeMar 13 Avr 2021 - 15:21 par Charly

» (Endurance) 24 heures du Mans 2021
250cc Air box design Icon_minitimeLun 12 Avr 2021 - 13:25 par BOOZE

» [GP] Moto GP 2021
250cc Air box design Icon_minitimeLun 12 Avr 2021 - 8:18 par herve

» [Oldies] Mettet, Mouscron, Chimay....
250cc Air box design Icon_minitimeDim 11 Avr 2021 - 17:09 par marco91

» [SORTIES] 12ème Sunday Ride Classic les 21 , 22 et 23 Mai 2021 - Circuit Paul Ricard
250cc Air box design Icon_minitimeDim 11 Avr 2021 - 16:18 par Jean-Luc Morchio

La réclame...
Mots-clés
motobecane RACING side honda 1974 Mans france geco daytona rouge 1973 oldies bresse 1980 aprilia bourg ducati charade zone wanted 1976 ROAD yamaha coupe 2013 suzuki
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 
Fügner
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
Jarno
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 
Dialmax
250cc Air box design Voting16250cc Air box design Voting13250cc Air box design Voting15 
La réclame...
Le Deal du moment : -55%
GETGO Set 6 boules de pétanque acier ...
Voir le deal
17.99 €

 

 250cc Air box design

Aller en bas 
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 2021 - 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 : 1591
Age : 64
Localisation : 40 Landes sud
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 2021 - 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 : 2395
Age : 72
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 2021 - 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 : 1591
Age : 64
Localisation : 40 Landes sud
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 2021 - 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 : 2395
Age : 72
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 2021 - 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 : 1591
Age : 64
Localisation : 40 Landes sud
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 2021 - 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 2021 - 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 : 2395
Age : 72
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 2021 - 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 : 1148
Age : 71
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 2021 - 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 2021 - 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 2021 - 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 2021 - 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 : 2395
Age : 72
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 2021 - 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 2021 - 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 : 295
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 2021 - 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
-
» Lebrunet - Design for you
» Julie Racing Design
» Design, mon beau design
» KS Design
» Enfin des gilets de sécurité design!!!

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