Want to learn about superjet intake

ISeeWetPeople

ISeeWetPeople

Location
Finland
So every time i see something new about superjet and i dont know what it is i want to learn it.. so the other day i was building my first stock ski and when i took intake manifod to my hand i start to wondering why are those connected before valves? So i thought about it and only reason for it i figure is pulse. Am i right?
 
Harbor

Harbor

Location
Stockton
Not sure what your question is. However, The pulse signals are in the crankcase, between the reeds and the piston. Theirs no pulse signal in the intake manifold, only varing amounts of low pressure to atmospheric pressure, depending , in part on throttle blade position.

Oh are you talking the crossover channel ?
 
ISeeWetPeople

ISeeWetPeople

Location
Finland
"The passage is originally intended to offer smoother low-speed response for the stock engines"

There is my answer.. but still dont know how it works tho..

Yes i know where and how carb pulse and singnal comes from=) i just thought that only one carb has signal in dual stock 38s from the case so how does the otherone gets it.. i thought that does this crossover channel "split" that signal so the second carb too gets it.. but then i remember that it gets it via fuel.. only one pump so... ive only had single carb kawi and then dual novi 48 so i had no idea how dual one pump carbs workd. That is until i thought it over..

But if i get it right.. blocking that channel gets you better carb singnal and more high peak power? So if i do it i shoud use even higher pop-off than stock 55psi? And for jettings i should get bit bigger?

sorry for bad english but its hard to write language that you suckd in school:( i had lowest grade possible:p
 
ISeeWetPeople

ISeeWetPeople

Location
Finland
Sorry i write wrong jettings should be smaller..

Im building this superjet using all the parts that i have left over in my carage..

So im building heavy ported 760 61x cylinder 62t case epoxy ported. I had only dual 38 to use with this and boyesen reeds stock fa stock electrics and flywheel.. i was planig to use low 80 and high 150 jets and 55pop-off but if i block that channel what should i try then
 
mbrick

mbrick

Location
Los Gatos, CA
The pulse signal line is for operating the fuel pump. Only one carb has the pump built in, which supplies fuel to both carburetors.
If you look at the routing, inlet into one carb -> routes out of the pump to 2nd carb -> return from 2nd carb to tank.

You are asking why the intake manifold crossover passage right before the reed cages exists. I can't answer that for sure... guessing as others have stated it smooths out the idle and bottom end? Yamaha would not add it for no reason.

With it filled each carb would only be feeding fuel to that individual piston and there would not be mixing.

Then again maybe the crossover allows a little more leniency in tuning because each carb is feeding a small amount to the other cylinder.

Others have stated it will richen due to a stronger signal on the single carb.
 
Quinc

Quinc

Buy a Superjet
Location
California
There is a thread where a guy claims it works like a boost bottle.


How does a Boost Bottle improve performance? Air rushes thru the carb on the intake cycle. Ignition accelerates the piston down, forcing the reeds to snap shut. The momentum (inertia) of the air has to go someplace. It goes back thru the carb causing a double rich mixture. The result can be rough idle or hesitation.

Due to the high velocity of the fuel air mixture through the carb boot, we need to take advantage of this momentum/inertia energy. The Boost Bottle and tube provide storage for the fuel air mixture between carb boots. The energy (pulse) forces the pre-atomized mixture in the tube from the previous cycle into the adjoining carb boot where the reeds are just opening and ready to receive the fuel air mixture. The boost bottle and tube provide a "boost" supercharge effect to each cycle.

The boost bottle is most effective at lower and mid-range rpm, and, when you are on & off the throttle. It assists in filling the cylinder (shorter distance) for a fraction of a second until the carburetor venturi gets enough velocity to fully atomize the fuel. The advantage is that it brings up the torque and horsepower in the bottom of the rpm range, up to where the pipe(s) starts to work. There is a small benefit at high rpm's.
 
ISeeWetPeople

ISeeWetPeople

Location
Finland
Quinc said:
There is a thread where a guy claims it works like a boost bottle.


How does a Boost Bottle improve performance? Air rushes thru the carb on the intake cycle. Ignition accelerates the piston down, forcing the reeds to snap shut. The momentum (inertia) of the air has to go someplace. It goes back thru the carb causing a double rich mixture. The result can be rough idle or hesitation.

Due to the high velocity of the fuel air mixture through the carb boot, we need to take advantage of this momentum/inertia energy. The Boost Bottle and tube provide storage for the fuel air mixture between carb boots. The energy (pulse) forces the pre-atomized mixture in the tube from the previous cycle into the adjoining carb boot where the reeds are just opening and ready to receive the fuel air mixture. The boost bottle and tube provide a "boost" supercharge effect to each cycle.

The boost bottle is most effective at lower and mid-range rpm, and, when you are on & off the throttle. It assists in filling the cylinder (shorter distance) for a fraction of a second until the carburetor venturi gets enough velocity to fully atomize the fuel. The advantage is that it brings up the torque and horsepower in the bottom of the rpm range, up to where the pipe(s) starts to work. There is a small benefit at high rpm's.
Click to expand...


Make sense..

but does this "inertia" have any time to go anywhere? the speed this is happening is so high? 7000rpm

maybe its there to help carb signal..?
if you think that engine is running 7000rpm piston 1 will suck the air gasoline mixture from its carb ( number 1 carb) but at the same time it will take this "inertia"air from the crossover channel from carb 2 so it will build underpressure/faster signal or response to carb 2..

how about if we talk this in finnish so i could explane my self better=)
 
You must log in or register to reply here.
Top Bottom