ini saya ambil dari site mirafiori.com, arsip forum lama. aslinya saya tulis dibagian bawah (sumber pustaka) selebihnya hanyalah translasi dan sedikit mikir2. namanya juga hasil mikir2, belum tentu bener. butuh komentar dari temen2 semua.
oya, untuk yang senang retro dan jadul, di mirafiori.com banyak banget informasi berharga. sayangnya doi blom ada versi bahasa indonesia, jawa ato sunda.
Emulsion tube action.
main well=lubang tempat emulsion tube ditanam
emulsion tube=tabung mixture yang bentuknya mirip suling
air corrector jet=spuyer angin
main jet=spuyer bensin
faktor penentu dari emulsion tube adalah diameter , number, dan lokasi lubang pada batang tube.
Udara diperoleh dari air corrector jet yang ditanam pada bagian atas tube (bisa drat atau tanam). udara yang masuk ke correction jet mengalir melalui lubang2 tube (pada batang) dan bercampur dengan bensin didasar tube.
bensin pada emulsion tube masuk via main jet pada bagian bawah tube (bisa drat atau tanam).
didalam tube, bensin melewati dasar tube melalui lubang2 tube dan bercampur dengan udara (so, its a mixture) bergerak keatas tube sampai ke auxiliary venturi (its a 'pancuran', kalo kite bilang hehehe).
pada saat idle/low speed, kondisi beban mesin ringan, tinggi permukaan bensin pada dasar tube akan sama dengan permukaan bensin pada pelampung/float chamber. bensin yg tersedia didasar/main well menolong memperkaya mixture pada saat beban bertambah/akselerasi.
kesimpulan:
1. emulsion tube tipis akan menyisakan lebih banyak ruang pada main well sehingga lebih banyak bensin tersedia untuk sedotan awal. yg tebel? ya sebaliknya atuh, persediaan bensin dikit.
2. sedotan awal mixture (saat dibejek) akan lebih kaya jika ngga ada lubang dibagian atas tube karena lubang dibagian atas melewatkan lebih banyak udara dan membuat mixture miskin (lean)
jadi si tabung emulsi ini punya dua kondisi ekstrim:
thin tube without upper holes - rich.
thick tube with large upper holes - weak
faktor diatas hanya berlaku pada saat initial draw/sedotan awal sebelum persedian bensin pada main well habis. setelah habis, supply bensin hanya didapat dari main jet.
tetapi ingat, ini diluar konteks ukuran main jet/air corrector yang dipake yahhhh
--cut--
so, gimana dengan uno kita?
kalau diliat dari atas seh, tabung emulsi uno ini bedanya cukup ekstrim. satunya gendut, satunya kurus.
yang gendut-f74 mixturenya lean/irit dan satunya lagi-f25 kaya/boros
mana yang peruntukan primer dan sekunder?
menurut bukunya seh f74 diprimer dan f25 disekunder. f74 setelan irit untuk beban rendan, f25 untuk beban menengah-atas (beban berat ada bantuan pompa akselerator -- diluar konteks tabung emulsi).
itu udah pas, percaya deh, yg bikin insinyur teknik bukan politikus. kalo yg bikin terakhir tu ngga bakalan pake tabung emulsi, ambil mentahnya aja disakuin buat nambah2....
gimana pengaruhnya kalo kebalik?
teorinya seh kalo kena macet tiap hari kaya jakarta gini berasa boros dan atasnya ngempos *subyektif, penuh perasaan, ato kadang2 malah rasanya ga banyak ngaruh* jadi buktiin aja sendiri
gimana kalo dua-duanya pake f74?
teorinya bilang lebih irit, tenaga loyo. hayo buktiin...
gimana kalo primer-sekunder sama2 pake f25?
hihihi...mo balap yaaaaa
kalo niat banget, itu ngga cukup. coba pake spuyer bensin yang sama2 rada gede diprimer dan sekunder trus mekanisme bukaan skep sekunder diubah jadi berbarengan dengan skep primer (progresive jadi sinkron, huhuyy). yah....jadi DCOE gadungan gicuuuu
mana yang saya pake?
standar ajaaahhhhhhh
sumber pustaka: arsip forum mirafiori.com, aslinya:
"Weber bible" (copied verbatim)
Emulsion tube action.
The controlling factors of the emulsion tube are its diameter
and the number, size and location of holes.
Air is admitted through the air corrector jet which screws into
the top of the tube or may be pushed into the tube. Air coming
through the correction jet flows out through the holes drilled
in the tube and mixes with the fuel in the emulsion tube well.
The fuel in the emulsion tube will come through the main jet
which may be screwed into the carburetor body or pushed into the
bottom of the tube and seats against the bottom of the well.
From inside the tube, fuel passes into the well through holes
drilled in the tube and mixes with air towards the top of the
tube before travelling to the outlet from the auxiliary venturi.
At idle or low speed, low load engine conditions, the level of
the fuel in the well would equal that in the float chamber. This
reserve of fuel helps to richen the mixture as engine speed or
load increases. two factors, therefore, become evident.
Firstly, a thin emulsion tube will leave more room in the well
for a larger reserve and conversely, a thick tube will lessen
the reserve.
Secondly, the initial draw of mixture from the well as the
throttle is opened will be richer if there are no holes in the
upper part of the tube, holes in the upper section of the tube
will admit air and weaken the mixture.
To cite the two extremes - a thin tube without upper holes -
rich. A thick tube with large upper holes - weak.
The foregoing action will only occur during initial
acceleration, as once the reserve in the well has been used, the
main jet is the only supply in this particular circuit.
Changing the emulsion tube is preferable to richening the pump
jet to overcome initial hesitation. The effect of and over rich
pump jet is disguised at higher engine speeds but has a large
bearing on economy. This is particularly evident in the DCOE
series where the pump circuit becomes a power circuit under full
load conditions"
An F30 tube is 6.2mm OD (a)3.5mm ID(b)
it has 4 x 140 holes close to the top (c)
has another 4 x 140 holes a little lower down (d)
has another 4 x 115 holes a little further down again (e)
has another 2 x 115 holes below these (f)
has another 2 x 115 holes below these (g)
and down at the bottom are 4 x 150 holes that admit fuel into
the jetwell (h)
this is getting pretty close to the example of the lean extreme
(for racing use) 6.2 mm is about the thickest tube you can get
for the dmtr/dcnf type carbs and this tube has lots of holes
(f32 is 7mm, this is the thickest on my list)
An F24 on the other hand is 5mm OD (a) and 3mm ID (b)
it has 4 x 150 holes close to the top (c)
has another 4 x 150 holes in the middle (e)
has another 4 x 200 holes to admit fuel into the jetwell (h) as
well as the lower drilling continues into the upper one,
(unlike an F30 which is seperated by solid brass)
an F24 is one of the richer emulsion tubes, and I have found it
to be more suited to spirited driving,
I have these in my 34datra 15/100 25/27 chokes (reamed to 26/28)
on my 1500 sohc X19
Im not saying these are "the" tube to use, but possibly you
should get hold of a selection chart, and try some different
tubes to feel the difference
