please explain the venturi effect

[sdiesel]

can you explain to me the venturi effect as it might apply to the following.
suppose i used a ford intake manifold, the one barrel manifold. put a carb on it , but weld a pipe between two steel flanges creating a small tower for the carb to sit on.
i couldn't understand the math in wikipedia for precise calculations, but if i undersized the tower pipe smaller than the carb bore and the plenum bore,
would i create a venturi effect,?
the hope would be to do this:
a. increase vacuum signal

b. speed the air fuel mix into plenum. zoom!
where
c. the air meets a divider sitting on the floor of the plenum. this divider looks like a triangle with concave sides that will sweep all rushing air to the left and right thusly decreasing turbulence and time needed to deliver to valves, the air furl charge, and hopefully holding the fuel in suspension if its moving faster.

if this is true i can reduce heat to the intake manifold.
i can also by lifting the carb reduce the potential for fuel boil.


thx

 

[mike1157]

Personally,..if you are talking about the 300 that is in your signature,..I wouldn't mess with it. Between the aftermarket where there are numerous carbureted offerings, and the factory making a viable F/I manifold for this thing that could be harvested off of a JY donor,.for probably next to nothing,....why try to re-invent the wheel?

The R&D science that goes into the design of an intake manifold from the aftermarket is already well vetted. I doubt there would be anything gained from some added 3 mile island looking tower under your carb other than compromised clearance , and a latent fuel signal coming from the carb that would cause a stumble at low RPM.

 

[bubba22349]

can you explain to me the venturi effect as it might apply to the following.
suppose i used a ford intake manifold, the one barrel manifold. put a carb on it , but weld a pipe between two steel flanges creating a small tower for the carb to sit on.
i couldn't understand the math in wikipedia for precise calculations, but if i undersized the tower pipe smaller than the carb bore and the plenum bore,
would i create a venturi effect,?
the hope would be to do this:
a. increase vacuum signal

b. speed the air fuel mix into plenum. zoom!
where
c. the air meets a divider sitting on the floor of the plenum. this divider looks like a triangle with concave sides that will sweep all rushing air to the left and right thusly decreasing turbulence and time needed to deliver to valves, the air furl charge, and hopefully holding the fuel in suspension if its moving faster.

if this is true i can reduce heat to the intake manifold.
i can also by lifting the carb reduce the potential for fuel boil.


thx

Personally as I understand it the Venturi Effect besides making a carberator work by its pressure drop and speeding up the flow. It's also how an aircraft wing produces lift and a part of how a Jet or Rocket engine also functions. See below link for a short Video explaining how it works and the formula used to calculate. Hope this is of some help to you, good luck on your intake project

https://m.youtube.com/watch?v=H3TcLoapJBo

 

[sdiesel]

on my sixes , all of them work engines in trucks, ive used lotsa manifold / carb combos.

im told that the short runner cast iron is good for lower rpm torque . im using a fish this time
i had used the fish with the "C" and a clifford. great for high rpm car . not so helpful on a truck.


this log manifold is a cleaner install, no adapters and im trying to improve effficiency of air delivery especially since a fish relies entirely on manifold vacuum.
i cannot push air in, i have to draw it in .
in a well vetted aftermarket manifold the distance from fuel to valve remains the same or even further and faces the same issues i am trying to address here:
which is :
will faster flowing air be created by a venturi , and will faster air hold fuel in suspension better.

efi manifold with carb is out of the question altogether, although that would be fun to try.

thx for video, i checked on that

 

[SteveP]

Bernoulli's Principle states that increasing the velocity of a fluid causes its pressure to be reduced. This is also sometimes called the "venturi effect".
The reduced pressure only occurs within the venturi. Once the air passes through the venturi the velocity is reduced and the pressure increases. You can only get an increased vacuum signal by tapping into the airstream within the venturi.
If you place a venturi between the carb and manifold you will increase air velocity and vacuum within the venturi but not before or after.