I was doing some thinking about the twin carb setup compared to the big single and why it works best. This is what i came up with. I am not an expert in physics so this explanation might have a few holes in it but here it is.....

It isn't just about volume (CFM). The single 50 might have more CFM than dual 38's. I haven't done the math on that.

What it is about is ramp rate and volumetric efficiency. Which setup do you think will be better suited to fill the cylinder more completely at low rpm?

Now which setup will be better suited to fill the cylinder more completely at high rpm?

The intake air is constantly starting and stopping as the vacuum signature of the piston dropping on the intake stroke gets blocked by the closed intake valves during combustion and the exhaust stroke.

Which carb setup will more easily pick up velocity and volume when the intake valves open again?

Here is the big one: Which carb setup has higher velocity? Intuitively the first response is to assume the smaller carbs will have more velocity but that is not true from a physics standpoint. In reality, velocity is volume over time. The smaller carbs are running about half the volume over a given time frame each as compared to the bigger carb so the smaller carbs each actually have much less velocity.

That means that the twin smaller carbs can move about the same CFM into the chamber but they can do it at a lower velocity with a much quicker pick-up from the vacuum signature. Knowing this begs the question which setup will have less turbulance and reversion in the intake ports? The setup with the least velocity will. Think about throwing a rubber ball at a concrete wall. The faster you throw it, the quicker and farther it bounces back. This is what happens to the air when the intake valves close.

This added efficiency and almost equal CFM allows you to maintain a higher VE at higher rpms.

The twin carbs will mean slower air measured at the carbs but they will provide faster and more focused air entering the cylinder.


Sorry for the book! Just some things to think about.

I was doing some thinking about the twin carb setup compared to the big single and why it works best. This is what i came up with. I am not an expert in physics so this explanation might have a few holes in it but here it is.....

It isn't just about volume (CFM). The single 50 might have more CFM than dual 38's. I haven't done the math on that.

What it is about is ramp rate and volumetric efficiency. Which setup do you think will be better suited to fill the cylinder more completely at low rpm?

Now which setup will be better suited to fill the cylinder more completely at high rpm?

The intake air is constantly starting and stopping as the vacuum signature of the piston dropping on the intake stroke gets blocked by the closed intake valves during combustion and the exhaust stroke.

Which carb setup will more easily pick up velocity and volume when the intake valves open again?

Here is the big one: Which carb setup has higher velocity? Intuitively the first response is to assume the smaller carbs will have more velocity but that is not true from a physics standpoint. In reality, velocity is volume over time. The smaller carbs are running about half the volume over a given time frame each as compared to the bigger carb so the smaller carbs each actually have much less velocity.

That means that the twin smaller carbs can move about the same CFM into the chamber but they can do it at a lower velocity with a much quicker pick-up from the vacuum signature. Knowing this begs the question which setup will have less turbulance and reversion in the intake ports? The setup with the least velocity will. Think about throwing a rubber ball at a concrete wall. The faster you throw it, the quicker and farther it bounces back. This is what happens to the air when the intake valves close.

This added efficiency and almost equal CFM allows you to maintain a higher VE at higher rpms.

The twin carbs will mean slower air measured at the carbs but they will provide faster and more focused air entering the cylinder.


Sorry for the book! Just some things to think about.