Simple Tunnel ram Question

[Kevin Johnson]

The question is a good one because it calls into consideration the effects of accelerating a partially closed system within another field of acceleration (gravity).

If a vehicle has forward acceleration the gases that have entered that construct will change in relative density because of reaction forces with its boundaries. The effect is real -- buy some helium balloons and place them in a closed vehicle cabin. If they are not restrained they will migrate fore and aft depending on the forward acceleration or deceleration of the vehicle.

A tunnel ram presents the least complex network of passages, so, under acceleration, fuel droplets have less of a chance to become less organized in cylinder to cylinder distribution (between groups analysis) or within that cylinder (within groups analysis). When going around passage bends, the mixed flow will stratify according to relative densities which would change while under forward acceleration or deceleration*, the latter probably being of less interest in a drag run. I do not know if OEMs model this behavior -- it would be expensive in terms of computing time. Jon could probably answer whether aftermarket companies consider this or at least one aftermarket company in particular.

* The droplets themselves once released do not receive any further acceleration save that by subsequent interaction with the gases and passage boundaries; there might be some measurable effect if constituents of the droplet with different vapor pressures migrated to the droplet boundaries and evaporated in an uneven manner, imparting thrust. I suspect droplets do not always have the opportunity to form perfect minimal surfaces.

[cardo0]

The gravitational constant is not used for 'direction'. The gravitational constant is used with gases to help determine their density.

And, yes... looking down the carburetor and seeing a straight shot at the valve does indeed pay dividends. Tunnel rams will always have their place with the folks who have the balls to use them.

You didn't bother to look at Bernoulli's equation. Density is a separate constant multiplier for another variable. No the gravitational constant is not used to determine the density. You have confused the gravitational constant is used when converting mass to weight but that is not the case in Bernoulli's equation.

[MadBill]

... buy some helium balloons and place them in a closed vehicle cabin. If they are not restrained they will migrate fore and aft depending on the forward acceleration or deceleration of the vehicle...

And people are often surprised to note that when the brakes are tapped, the passengers' heads bob fore but the balloons rush aft...

[cjperformance]

... buy some helium balloons and place them in a closed vehicle cabin. If they are not restrained they will migrate fore and aft depending on the forward acceleration or deceleration of the vehicle...

And people are often surprised to note that when the brakes are tapped, the passengers' heads bob fore but the balloons rush aft...

Yes , the air has mire weight than the helium ballon, hit the brakes and the air in the cab continues forward creating a slightly higher pressure and density at the front of the cab, the lighter helium balloon then migrates to the lower pressure area at the rear of the cab .

[MadBill]

It also happens with just air. In below zero (°F.) weather, when you hit the brakes in a station wagon, you can feel a tide of cold air from the rear compartment wash over your feet.
(And now who's contributing to topic drift? )

[Tuner]

I'll try this one more time. Buoyency is not a factor in this. Acceleration is the factor. Earth's gravity affects any object accelerated toward or away from "down". Before entering an engine the air is at rest and must be accelerated from the at rest condition to whatever is the port velocity of the particular engine. Exaggerating the mass involved makes clear the effect of Earth's gravity, imagine throwing a baseball either straight down or straight up. Buoyancy can be disregarded. The air is imparting a buoyant force on the baseball, just not enough relative density to be obvious, for example as it would if the ball were floating in Mercury. To achieve equal velocity in either up or down direction requires less applied acceleration force energy toward "down" and more toward "up". The obvious (can't see the forest for the trees .. obvious) factor is Earth's gravity assists downward acceleration of anything, including air In the tunnelram.

The point in mentioning an upside down engine was to illustrate the need to accelerate the weight of air from zero to port velocity. 650 HP requires approx. 1000 CFM. 1000 cubic feet of standard air weighs approximately 75 lbs. and will be accelerated from zero to approximately 300 fps. The acceleration force of gravity is always there and to compare updraft to down draft was to illustrate the intake air's weight is either being lifted or falling. Accelerating the air from zero to port velocity is a portion of an engine's pumping loss. In a tunnel ram with vertical down-draft runners, gravity assists the acceleration of the air.

[Tuner]

It also happens with just air. In below zero (°F.) weather, when you hit the brakes in a station wagon, you can feel a tide of cold air from the rear compartment wash over your feet.
(And now who's contributing to topic drift? )

Perhaps not if you are driving a '58 Buick. Those cars have hot engine water piped to a pair of heat exchangers, one on each side, under the front seat.

[j-c-c]

Well then, if just gravity is a plus notable factor, would in say a typical drag application, leaning all the runners somewhat forward, also then give further advantage because of the car's acceleration?
Or are we losing the the straight shot inherent advantage if we lean too far?

What range of G's of acceleration are we talking about anyway?

[n2omike]

I'll try this one more time. Buoyency is not a factor in this. Acceleration is the factor. Earth's gravity affects any object accelerated toward or away from "down". Before entering an engine the air is at rest and must be accelerated from the at rest condition to whatever is the port velocity of the particular engine. Exaggerating the mass involved makes clear the effect of Earth's gravity, imagine throwing a baseball either straight down or straight up. Buoyancy can be disregarded. The air is imparting a buoyant force on the baseball, just not enough relative density to be obvious, for example as it would if the ball were floating in Mercury. To achieve equal velocity in either up or down direction requires less applied acceleration force energy toward "down" and more toward "up". The obvious (can't see the forest for the trees .. obvious) factor is Earth's gravity assists downward acceleration of anything, including air In the tunnelram.

The point in mentioning an upside down engine was to illustrate the need to accelerate the weight of air from zero to port velocity. 650 HP requires approx. 1000 CFM. 1000 cubic feet of standard air weighs approximately 75 lbs. and will be accelerated from zero to approximately 300 fps. The acceleration force of gravity is always there and to compare updraft to down draft was to illustrate the intake air's weight is either being lifted or falling. Accelerating the air from zero to port velocity is a portion of an engine's pumping loss. In a tunnel ram with vertical down-draft runners, gravity assists the acceleration of the air.

You're mistaken, but I'm tired of trying to teach you.
Gravity has nothing to do with how a tunnel ram works.
Same principal as a why a water balloon doesn't sink underwater.
There is no net gravitational force.
Carry on...

[Tuner]

The factor you are failing to grasp is ACCELERATION. What effect does Earth's gravity have if you apply an outside force to accelerate your balloon of water down or up from an at rest condition to 300 FPS in 18 inches. Will gravity help or hinder if the balloon is accelerated down or up? Gravity is an ever-present force and cannot be ignored.

[MadBill]

Per previous reference:
"Newton's second law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object. As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased."

Since ambient air pressure (which as previously posted is a result of gravity acting on the molecules that make up air) applies equally in all directions, there is no 'net force' of gravity acting downward on the air and so its acceleration into the intake tract is determined only by the pressure drop from ambient to manifold.

Another example would be just standing on the ground. Gravity acts upon your body with a force of one G, which is opposed by an equal reaction force from the ground, resulting in no net force and thus zero acceleration. Now, step off a cliff: The ground reaction force is now absent and you accelerate downwards at an invigorating one G...

[Tuner]

A portion of the net force is the acceleration of gravity, which is either a positive force, in the case of "down", or a negative force, in the case of "up". The acceleration force of gravity is always there. If you can figure out how to shield gravity, or "anti-gravity" in effect, you will not only be able to buy Speed Talk, you can buy the whole internet.

[SchmidtMotorWorks]

I am not certain that the buoyancy argument applies given the cylinder is not open at the other end.

Let's consider the model below:

If gravity did play a factor in this it seems that air would flow into the upper duct and out the lower duct (i think we can agree it doesn't)

If the system had a 3rd duct pulling a small depression from the inside of the box so that air could flow into the box from either duct...

If gravity mattered there would be a difference in flow in the upper and lower duct.

If the above is true, it seems that there would be a low level of vacuum where the upper duct has flow and the lower duct does not. (I doubt that is true)

tunnel_ram.jpg

[n2omike]

If gravity did play a factor in this it seems that air would flow into the upper duct and out the lower duct (i think we can agree it doesn't)

The ONLY role gravity plays, is its part in providing the pressure differential.
It doesn't matter if the carbs are updraft, downdraft or sidedraft. Makes ZERO difference. The pressure differential is the same.
The buoyancy example was to show that gravity alone is not providing a NET force on the air column in any given direction.
Gravity's sole role is it's part in providing the pressure differential.

[MadBill]

A portion of the net force is the acceleration of gravity, which is either a positive force, in the case of "down", or a negative force, in the case of "up". The acceleration force of gravity is always there. If you can figure out how to shield gravity, or "anti-gravity" in effect, you will not only be able to buy Speed Talk, you can buy the whole internet.

What makes you so certain you're right and all others are wrong? If you think there's a gravity term missing from Newton's 2nd law of motion and you can prove it, you'll have overturned 350 years of scientific belief.

How about a test? When flowing an exhaust port, fit a pipe to it with a 90° bend, swivel it up and down and compare flow. If gravity is a factor of any consequence, the port will flow better with it pointing down, allowing the air to more readily fall out.