Would placing a right angle (down) elbow , perhaps similar to intake stacks on hot rods, etc., enhance air flow to a stock carburetor ? Was thinking to use an Air Maze without the screen, (which restricts air flow) in combination with stock engine pans. if there is empirical tested data, such as fuel air ratio disruption, that would be helpful.
Carb Intake throat enhancement
- Thread starter SAXBY2
- Start date
Joe K
Well-known member
I can't give you empirical data, but I can indicate to you "equivalency" of pipe (tube) in an engineering sense.
For years, a guide has been used by piping engineers. "Flow of Fluids Technical Paper 410" by the Crane Company (valve manufacturer) In the book they give "equivalency" of various patterns of fitting compared to "straight pipe" of the same size.
In your case the equivalent length of straight pipe to your elbow would be 30 diameters of the pipe. For a 1-1/2" inlet, it would be like adding 45 inches of straight pipe to the intake. Any pipe you add to create a "intake stack" would be added on top of the 45 inches represented by the elbow alone.
Rule of thumb: EVERY amount of pipe you add adds RESISTANCE to the flow - and impedes total air flow. And reduces total air volume carried.
For your engine volume equals oxygen which in effect reduces the power you will create. I.e. you will have to burn less fuel to not create the "choking" effect of too much fuel for air. Less fuel means less power.
Hence the introduction in WWII of super and turbo-chargers to increase the total air flow and allow larger amounts of fuel to be burned - and more power created.
This is not the answer you want - and the only exception I might think to this would be one which utilizes the "pulsing" character of engine intakes, and the "timing" this introduces to your air flow. Otherwise known as "tuning" your intake. Just as you can "tune" your exhaust to utilize better the "inertia" of gas in motion leaving the engine and clear your cylinders of exhaust better.
This equivalency is a "sonic rush" if you will and is related to the velocity of sound in air.
Bulletin 410 doesn't address "tuning" specifically - but there are separate guidelines developed with most engine builders having their own "secret tuning." They have figured out based on the engine operated speed what is the optimal length of pipe to route the air to and from their use without having an effect on the total air provided.
Best might be to leave it alone - or work on the manifolds/piping downstream of the carburetor to further decrease a resistance.
Joe K
For years, a guide has been used by piping engineers. "Flow of Fluids Technical Paper 410" by the Crane Company (valve manufacturer) In the book they give "equivalency" of various patterns of fitting compared to "straight pipe" of the same size.
In your case the equivalent length of straight pipe to your elbow would be 30 diameters of the pipe. For a 1-1/2" inlet, it would be like adding 45 inches of straight pipe to the intake. Any pipe you add to create a "intake stack" would be added on top of the 45 inches represented by the elbow alone.
Rule of thumb: EVERY amount of pipe you add adds RESISTANCE to the flow - and impedes total air flow. And reduces total air volume carried.
For your engine volume equals oxygen which in effect reduces the power you will create. I.e. you will have to burn less fuel to not create the "choking" effect of too much fuel for air. Less fuel means less power.
Hence the introduction in WWII of super and turbo-chargers to increase the total air flow and allow larger amounts of fuel to be burned - and more power created.
This is not the answer you want - and the only exception I might think to this would be one which utilizes the "pulsing" character of engine intakes, and the "timing" this introduces to your air flow. Otherwise known as "tuning" your intake. Just as you can "tune" your exhaust to utilize better the "inertia" of gas in motion leaving the engine and clear your cylinders of exhaust better.
This equivalency is a "sonic rush" if you will and is related to the velocity of sound in air.
Bulletin 410 doesn't address "tuning" specifically - but there are separate guidelines developed with most engine builders having their own "secret tuning." They have figured out based on the engine operated speed what is the optimal length of pipe to route the air to and from their use without having an effect on the total air provided.
Best might be to leave it alone - or work on the manifolds/piping downstream of the carburetor to further decrease a resistance.
Joe K
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nkaminar
Well-known member
A little while ago there was a study that indicated that the elbow improved flow. I cannot remember whether the elbow pointed up or down. The elbow set up the flow at the elbow built into the carburetor where the venturi lives to improve the flow.
In general, as Joe K talked about, adding any bend will reduce the flow. But in this case the elbow improved flow because it set up the air flow to the venturi. The effect is very small and changing out the carburetor for something that will flow more air, and at the same time changing out the manifold, will do a lot more to improve performance.
In general, as Joe K talked about, adding any bend will reduce the flow. But in this case the elbow improved flow because it set up the air flow to the venturi. The effect is very small and changing out the carburetor for something that will flow more air, and at the same time changing out the manifold, will do a lot more to improve performance.
Big hammer
Well-known member
Elbow pointing down , I believe it was Dave Renner’s testing !
Fullraceflathead
Well-known member
When it comes to elbows a sharp 90 ° is very restrictive and causes a lot of turbulence In an ideal situation you want a very large radius smooth Elbow for minimum restriction!!!
Bob Bidonde
Well-known member
Fluid flow through an elbow causes a pressure increase as it impacts the far wall of the elbow. Consequently, there is a pressure drop on the near wall of the elbow. The result is a disruption in laminar flow (turbulence). In my 46 years of engineering, never have I seen fluid tubing designs with elbows to enhance the fluid flow. Just the opposite, bends & elbows were avoided wherever possible.
If an improvement in the intake air flow is a goal, try cutting away that part of the venturi that is visible behind the choke in a Zenith carburetor. Also, do not use any kind of an inlet air filter. Also make sure there are no manifold / carburetor shaft/ windshield wiper vacuum leaks.
If an improvement in the intake air flow is a goal, try cutting away that part of the venturi that is visible behind the choke in a Zenith carburetor. Also, do not use any kind of an inlet air filter. Also make sure there are no manifold / carburetor shaft/ windshield wiper vacuum leaks.
nkaminar
Well-known member
The right angle elbow associated with the filter, and the inlet to the carburetor, are large diameter compared to the venturi. This may have something to do with it. There are two ways to determine what is actually happening. One is to model the flow on a computer, the other is what was done in 1930 and that is to set up a bunch of pitot tubes in the carburetor to actually measure the flow.
Someone, Big Hammer thinks it was Dave Renner, actually measured an increase in power with the elbow installed.
The Model A carburetor design is actually fairly clever. The larger diameter entrance leading to the smaller diameter venturi minimizes any flow loss from the right angle turn at the venturi.
I am going to guess that the elbow crowds the air towards the top of the carburetor inlet which makes the turn at the venturi more efficient.
Someone, Big Hammer thinks it was Dave Renner, actually measured an increase in power with the elbow installed.
The Model A carburetor design is actually fairly clever. The larger diameter entrance leading to the smaller diameter venturi minimizes any flow loss from the right angle turn at the venturi.
I am going to guess that the elbow crowds the air towards the top of the carburetor inlet which makes the turn at the venturi more efficient.
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Y-Blockhead
Well-known member
I fabbed and installed a scoop on my Marvel, don't know if it makes more power. My goal was not sucking air directly off the exhaust manifold. If nothing else, I think it looks "racy"...
Thanks Y block; that's what I had in mind for my Marvel as well , using just the air maze elbow. Your's looks better and a softer angle, kind of like stacks on top of hot rod 3-2's.
Perhaps heated air from the manifold is beneficial for cold weather start ups.
How is the copper attached to the throat ? When I employed K&N air filters, I used a radiator hose type of coupling with straps.
You may have have air rush from the fan and louvers.
Perhaps heated air from the manifold is beneficial for cold weather start ups.
How is the copper attached to the throat ? When I employed K&N air filters, I used a radiator hose type of coupling with straps.
You may have have air rush from the fan and louvers.
Attachments
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Gene F
Well-known member
Saxby, since you have the Marvel, have you thought about buying one of those intakes from Snyders that has the larger bore, and leaving it at that? Seems like one thing everyone agrees on is that more air (and fuel) going into the thing will give you more power.
Lots of interesting comments on this thread.
Lots of interesting comments on this thread.
Gene F
Well-known member
A larger bore intake manifold. Call them, They sell them.
Y-Blockhead
Well-known member
Actually I was looking for cooler air away from the exhaust manifold. Cool air is denser than hot air so you get more O2.
Synchro909
Well-known member
I think this one one of those things that are difficult to arrive at a decision on "cranially", IMO, it would be imperical testing that would give the answer. I suspect you are partly right in that thought but I have heard (and can't disagree with) the suggestion that warm air helps atomise the fuel and on a cold morning, helps prevent ice accumulating in the carburettor.
For every up, there is a down. Where is the best balance?
alexiskai
Well-known member
According to Dave Renner, who actually did do a flow analysis of this scenario, mounting the Air Maze elbow (but not the maze itself) with the opening downward slightly increases flow through Zenith carbs. I don't have his data, and he may not have the records any more. He discovered this by accident while writing an article on air-balancing. And he did say "slightly," so we may be talking <5% improvement. Also this was bench testing, so he was not modeling the air flow in the engine bay with the fan going, pans in place, etc.
If I were doing this, I would consider popping the elbow on there if I already had one or got one free, but I wouldn't go out and buy an Air Maze for this purpose.