Single carb vs dual

[waxhead]

I know where your going with your theory but it doesn't work out like that. You think that since its going to seperate cylinders it means it can flow more as each cylinder is pulling at different times.
Sounds good but it doesn't work quite the same as that. Plus when the reeds close it sends a shock wave back up the intake which forces fuel back up with it. We call it stand off this is one of the reasons that novi made f boosters as well as d boosters for their carbs. But the reality is it helps stall flow in the intake for the other cylinder. So in fact it's worse as the mixture has to deal with the pulses from other cylinders as well

But both 38's arent feeding a single cylinder together. Each 38 is feeding a single cylinder.

 

[WB1994]

You said the two 38's combine for bigger flow but they arent both flowin to both cylinders. Thats all.

 

[waxhead]

The full flow of the 46 is not going to both cylinder either its shared.
But give it a go and see how it works out. You may get it to run very well

 

[WB1994]

Are you saying that at no point of the prosses is the single 46 flowing all 46 ?

 

[waxhead]

Are you saying that at no point of the prosses is the single 46 flowing all 46 ?

Can you highlight where you saw me say that. Im not sure how you got that and I will try and explain it better to you

 

[WB1994]

The full flow of the 46 is not going to both cylinder either its shared.

What I meant to say is each cylinder never sees a full 46?

 

[waxhead]

It cant its shared between two cylinders other wise you would never bother bolting on twin 46mm carbs. you would simply buy one carb.
You also get a longer intake with the single carb as well which does not help throttle responce. It may do on a four stroke but not on a two stroke

 

[WB1994]

So both sets of reeds are always open? Thats the only way one side could never see the full 46 , right?

 

[waxhead]

So both sets of reeds are always open? Thats the only way one side could never see the full 46 , right?

No both sets of reeds are not always open, No not right on the 46.
But I am unsure how to explain it in a different way you would understand. So I suggest you give it a go and keep us updated on the progress

 

[kevbo]

I did a test between single 44 and twin 44s on the same engine. The single required 50% throttle to hit the pipe. Twins hit around 40% open. The twins needed to be set richer at part throttle for best response and consumed 15-20% more fuel for surf type riding. The twins made the pipe hit a little harder but did not turn any more rpm.

 

[WB1994]

So if one set of reed closes for a certain amount of time then whats that 46mm doing? I would assume pumping all 46 to one side or the other. Depending on which sides reeds are closed? right? Because the only time a carb stops performing , seing preasure through the carb , is when all reeds are closed , like on a dual carb setup.

 

[WB1994]

I did a test between single 44 and twin 44s on the same engine. The single required 50% throttle to hit the pipe. Twins hit around 40% open. The twins needed to be set richer at part throttle for best response and consumed 15-20% more fuel for surf type riding. The twins made the pipe hit a little harder but did not turn any more rpm.

Whats "hit the pipe" mean?

 

[waxhead]

So if one set of reed closes for a certain amount of time then whats that 46mm doing? I would assume pumping all 46 to one side or the other. Depending on which sides reeds are closed? right? Because the only time a carb stops performing , seing preasure through the carb , is when all reeds are closed , like on a dual carb setup.

All your assumbitions are based on the fact that air has no mass. However the fact that wind can pick up cars and blow them around tells us that this is not true.
Therefore the air is backing up behind the reed cage and does not in fact stall and change direction and go down the other carb. If this was the case then we wouldnt be running twins on free ride/ race boats but just a massive single
However as I said before go for it and see how it works out for you

 

[kevbo]

Whats "hit the pipe" mean?

I meant the amount of throttle opening required for the pipe to find resonance rpm. All else equal, a small carb will be opened more than a larger one at this reference point or any rpm below full power.

 

[WB1994]

I meant the amount of throttle opening required for the pipe to find resonance rpm. All else equal, a small carb will be opened more than a larger one at this reference point or any rpm below full power.

Interesting. Im going to ask another stupid question and I thank you for your patience. Whats resonance rpm?

 

[WB1994]

All your assumbitions are based on the fact that air has no mass. However the fact that wind can pick up cars and blow them around tells us that this is not true.
Therefore the air is backing up behind the reed cage and does not in fact stall and change direction and go down the other carb. If this was the case then we wouldnt be running twins on free ride/ race boats but just a massive single
However as I said before go for it and see how it works out for you

Doesnt that mean in therory if your reeds seal perfectly then all that mass in front of that reed is going nowhere and all that mass is creating/compleating the channel coming out of the carb and causing all the air to channel to the now open reed side? So that would mean all 46 is going to the open reed side because the closed reed side is full of mass? Which would mean all 46 goes back and forth side to side. And if thats true then wouldnt a single carb be getting a constant "on" signal? Whereas a dual carb , carb always gets an "on - off - on - off - on - off " signal?

 

[waxhead]

Doesnt that mean in therory if your reeds seal perfectly then all that mass in front of that reed is going nowhere and all that mass is creating/compleating the channel coming out of the carb and causing all the air flowing from the carb to channel to the now open reed side? So that would mean all 46 is going to the open reed side. Which would mean all 46 goes back and forth side to side. And if thats true then wouldnt a single carb be getting a constant "on" signal? Whereas a dual carb , carb always gets an "on - off - on - off - on - off " signal?

Thats the hardest thing to read, Whats this channel you speak of ??

Your theory tries to prove that a single carb is a good as a twin carb of the same size. I believe you should go for it and set it up. Unfortunatly for me "and every other tuner of high performance two strokes" I am still bound by the laws of physics.

 

[WB1994]

Yeah , I edited it a little but you quoted the origional.

Im just trying to figure out if all 46 goes to one side or not. You said not because of mass , or something. I said that would mean that both sides would have to have thier reeds opened at all times to some vairiable amount. Now Im confused.

 

[waxhead]

Good luck with your research

 

[WB1994]

You gonna leave me hangin? You said niether side ever gets all 46mm of goodness. You then said air has mass and when the reed closes, all that mass isnt going to exit that side of the intake. Its basicly trapped there. So in effect your saying that the intake side solid with mass is causing all the 46mm goodness to go to the open reed side .... ?