Intake plenum and 911 throttle body

[KRAM36]

Originally Posted by Ben006

I didn't read everything because I'm on my phone, but pulling air and pushing air is the same.
The engine does not pull air into it, the air is pushed inside because the atmospherique pressure is greater than the pressure inside the combustion chamber.

Yes, that's the principle of why air wants to "move into the engine", but the engine is working like a pump too. The downward stroke of the piston with the intake valve open creates a pull on the air into the cylinder. The rings on the piston are just as important to filling the cylinder with air as it is to the compression of the air.

[Jamesp]

Originally Posted by KRAM36

Yes, that's the principle of why air wants to "move into the engine", but the engine is working like a pump too. The downward stroke of the piston with the intake valve open creates a pull on the air into the cylinder. The rings on the piston are just as important to filling the cylinder with air as it is to the compression of the air.

So exactly how are air molecules joined together such that one can pull another? Little strings? High pressure pushing into low pressure is intuitively obvious, but low pressure "pulling" in high pressure? Puzzling.

[jsceash]

Originally Posted by KRAM36

Yes, that's the principle of why air wants to "move into the engine", but the engine is working like a pump too. The downward stroke of the piston with the intake valve open creates a pull on the air into the cylinder. The rings on the piston are just as important to filling the cylinder with air as it is to the compression of the air.

The instant the air starts to move Newton's laws apply. It doesn't mater if it suck through a pipe or push through a pipe the same principles apply. The same equations are used to calculate flow loss, flow velocity.

This must be another theory that doesn't apply and can't be taught in Kansas school.

[Ben006]

An engine is basically a pump, but the the air behave the same if you move it by droping the pressure on one side, or raising it on the other.
There is no such thing as vacuum, it's just a difference of pressure and that is what move the air, a fluid is never "sucked" it is always pushed from an area of high pressure to an area of low pressure.

[jsceash]

Air and water are Newtonian Fluids. A Newtonian fluid is any fluid that follow the same characteristics as a solid. Flow and velocity are base on friction and static attraction or a coefficient of viscosity. The calculations say ignore a negative number such as pressure because the value are squared so a negative pressure times itself is a positive value.

[KRAM36]

Originally Posted by Ben006

An engine is basically a pump, but the the air behave the same if you move it by droping the pressure on one side, or raising it on the other.
There is no such thing as vacuum, it's just a difference of pressure and that is what move the air, a fluid is never "sucked" it is always pushed from an area of high pressure to an area of low pressure.

Explain why on these charts the wedge makes no difference and in Pedro's video it does and he calls it pulling air and says there is an influence on the air

Originally Posted by blue2000s

I'm using Fluent in these simulations.

A Y will be more efficient than a T for airflow in a steady state, that's correct.

Keep in mind that with three cylinders to a plenum, there is a pretty much constant flow of air into the plenum when the engine is kept at a constant speed. There is always a cylinder pulling air. The pulses that influence secondary pressure waves are important, but they are secondary in nature so the influence on flow is on a much lower order than the primary vacuum pulled by the cylinders themselves.

Here are three more simulations varying on the one I posted earlier. The first one just adds a sloped wedge to the original T. The second adds a large radius to the T junction and the last one combines the radius with the wedge.





The volume flow rate results show that the T and T with wedge have almost identical flow rates. The radius-ed T with and without the wedge are both almost the same flow rates but are about 30% greater than the standard T.

We have this.

"A third factor in manifold vacuum is engine compression. If an engine has low compression in all cylinders, it creates a steady, but low, manifold vacuum. If an engine has low compression in one cylinder, manifold vacuum will be low only during that cylinders intake stroke. This will be observed as a gauge that fluctuates or quickly changes reading. Low compression in a cylinder can be caused by leaking valves or rings, leaking head gaskets, or other ways that keep the cylinder from sealing during the compression stroke."

Compression and Vacuum

Originally Posted by jsceash

The instant the air starts to move Newton's laws apply. It doesn't mater if it suck through a pipe or push through a pipe the same principles apply. The same equations are used to calculate flow loss, flow velocity.

This must be another theory that doesn't apply and can't be taught in Kansas school.

Do you know how to have a conversation without insulting someone? If you can't, you can go you know what yourself. Also read my location again smart guy, I don't live in Kansas.

[jsceash]

I give up
Believe what you want.

Sarcasm

Republican legislator from Missouri, offered a bill last month that would allow parents to pull their children out of high-school biology classes lest they be exposed to the concept of natural selection. Nearly 90 years since the public trial of John Scopes, a young schoolmaster accused of teaching evolution to Tennessee children, Missouri’s House Bill no. 1472

The earth is flat and Einstein was all wet

[jaykay]

I can see a wedge helping where you have the airflow motive force being dominated by constant "push" forces as would be present from a turbo or supercharger. The reason being that side to side pulses or draw into the engine from left to right, right to left plenums are fed positively from the turbo or super charge. The side to side pulse is not disrupted by the wedge.

When we consider NA there will pulses from plenum to plenum as the engine draws air in. This will be interrupted by the wedge. There is no positive charge to help feed this need.

Have a look at the IPD wedge. In many iterations you will see holes, relief features which I believe is a feature intended to mitigate this NA flow issue.

NA engines: wedge value is questionable

Boosted engines: wedge could help cylinder filling

> as always testing is needed to know

[KRAM36]

Originally Posted by jsceash

I give up
Believe what you want.

Sarcasm

Republican legislator from Missouri, offered a bill last month that would allow parents to pull their children out of high-school biology classes lest they be exposed to the concept of natural selection. Nearly 90 years since the public trial of John Scopes, a young schoolmaster accused of teaching evolution to Tennessee children, Missouri’s House Bill no. 1472

The earth is flat and Einstein was all wet

It's not what I believe, it's what I see. With the simulations the wedge makes no difference, then you have Pedro blowing air into the Distribution T and it makes a difference. So what is it that's making this difference? It has to be the way the air is being fed into the Plenum from Distribution T. The air is not hitting the back of the Distribution T (yes maybe a little), it's getting pulled along the side of the Distribution T's radius. That's what makes the 997 Distribution T so effective.

[KRAM36]

Originally Posted by Jamesp

So exactly how are air molecules joined together such that one can pull another? Little strings? High pressure pushing into low pressure is intuitively obvious, but low pressure "pulling" in high pressure? Puzzling.

I don't know James. How is dirt pulled into your vacuum cleaner? Is each piece of dirt attached to each other with a little string such that one can pull another? Gravity is pulling the dirt down to the Earth, but the vacuum has enough force to pull the dirt off the ground. The force of the piston can not move air?

I'm not a scientist, maybe I shouldn't comment on anything since I'm not. I'm just trying to help out. All I know is the simulation of the air flow through the Distribution T is not like putting a leaf blower in the end of the Distribution T and blowing air at it. There seems to be a difference in what our engine is doing with the air and what the leaf blower is doing with the air.

Maybe you can clear this up? Is the simulation incorrect? Help out if you know, throwing jabs at me doesn't help anyone.

[Jamesp]

As an engineer, it's entertaining to watch the other engineers try to explain technical principles to non technical folks. Without a technical education folks will believe what they want to believe (suction is a great example). At some point you just have to say, "I can explain it to you, but I can't understand it for you."

[jsceash]

Originally Posted by Jamesp

As an engineer, it's entertaining to watch the other engineers try to explain technical principles to non technical folks. Without a technical education folks will believe what they want to believe (suction is a great example). At some point you just have to say, "I can explain it to you, but I can't understand it for you."

I like that

[KRAM36]

Originally Posted by Jamesp

As an engineer, it's entertaining to watch the other engineers try to explain technical principles to non technical folks. Without a technical education folks will believe what they want to believe (suction is a great example). At some point you just have to say, "I can explain it to you, but I can't understand it for you."

I don't see where you explained anything? Try me, I'm not afraid to learn.

From the simulation. "The volume flow rate results show that the T and T with wedge have almost identical flow rates." Yet Pedro's video shows the opposite.

Originally Posted by jsceash

I like that

jsceash can you explain this? Is the simulation wrong? Did Pedro sneak a magic trick in on you? I can't imagine Pedro could pull one over on a smart guy like you.

[jsceash]

I'll try a different way.

Have you ever gone fishing in a trout stream and watched a bend in the stream with a back eddy. The water spins backward and slows as it gets away from the current the speed up as it comes back around. A portion of the stream flows back continuously. It really obvious if there is a can or foam cup floating in it. That is what happens in the long radius flat back Porsche Plenum.

Now imagine the same stream and same bend if someone built a concrete barrier in the outside radius. The water would glide past at a faster speed or equal to the rest of the stream current. The IPD and or Pedro's Plenum.

Pedro's video is a bit of truth a bit of exaggeration. It exploits the defect in the stock plenum. The dead space becomes larger as the velocity of air is increased it is a principle in air flow called a "Boundary air layer". "Turbulent boundary air" is proportional to the air velocity so the turbulent area increases as the air velocity increase. Pedro uses a vacuum to blow air in the plenum which creates a higher velocity than the NA motor can produce but it is fast enough to exaggerate the flow problem. I've been trying to explain all day that turbulent air is like a plug reducing flow. The second type of boundary air layer is "Laminar Boundary air" its the drag created from the air friction with surface of the pipe. This is proportional to the square root of the velocity so it increases slowly as the velocity increases so it has little effect in the application. The big thing you see this affect is golf balls put dimples in the surface you can defeat the effect. Pedro uses a Teflon insert which has a low friction coefficient. IPD used of epoxy coat them but now the shot peen the inside so it like the dimples on a golf ball either way they negate the effect at the air flow speeds for the application

[blue2000s]

Originally Posted by jsceash

The 997 T still has the same inherent issue with turbulence
Newton' laws of physics which apply to air as well as solid matter.
"An objects in motion stay in motion until acted on by an opposing force" The air entering the T will for the most part continue in the direction it is traveling towards the back of the T.
"Every action has an equal and opposite reaction" The air striking the back of the T will rebound into the air stream causing turbulence.

Bens design Pedro Techno Torque 1 and 2 and IPD are better solutions. The incoming air hits the flat back of the stock T and compresses before it move sideways causing not one but three turbulent areas one in the back high pressure and on the top where to low pressure accumulate at the radius to the inlet to the two exits. There are Cad test drawings showing how ineffective this is in one of these threads.
Pedro system the cheapest alternative. adds a deflector V in the back creating an actual flow Y. IPD all aluminum design is molded with the same V diverter Bens is a copy of IPDs design, which I doubt he will be allowed to sell due to patents from IPD. In the end there is about a 25% improvement in this design you can't get from the stock distribution T.

Look at the video from about 7 minutes in
https://www.youtube.com/watch?v=B-fXau-xWO8

The negative on IDP is the $795 price opposed to Pedro's or Ben's design. note the IPDs design is the same and it totally coated in epoxy inside.
https://www.youtube.com/watch?v=SneTb8-cHbo

I doubt anyone who has one of these designed systems would ever go back to the factory Distribution T.

This is going to be technical. Sorry, it has to be. The answer is recirculation. The slow moving air that naturally forms the wedge forms a high pressure zone that diverts the incoming flow. As Newton or more precisely Navier-Stokes would tell us is that the path of a fluid particle is influenced by the forces on that particle. The high pressure of the stagnated wedge diverts the streamline of air away from the back of the "T". So the air coming in from the throttle body never "bounces" off the wall. The effect of a physical wedge is more likely to disrupt the secondary pulsation supercharging effect of the tuned plenum than it is to help bulk flow in any way. A simple flow bench test will prove this out.

I know people like to refer to detached flow as "turbulence", but it's really not accurate (It's one of those things that annoys a fluids engineer). In reality, most flow through the engine is turbulent, which means that the air particles within the freestream is not generally taking a linear path. There is more energy in a turbulent flow, which helps keep the freestream attached to a surface. This is why they make airflow turbulent at the leading edges of airplane wings with little triangles and golf balls have dimples.

[KRAM36]

Wow, you haven't posted here in over a year blue2000s. Thanks for the explanation. So what is it about the radius that makes it flow 30% better? Does the larger radius give the air more room to move inside the Distribution T because it's already making it's own natural wedge which would reduce the area for the air to flow?

Yeah, me thinking the engine was making the air pull to the radius looks really stupid, well at least to you guys lol. I never thought about the air creating it's own wedge and I'm trying to figure out why this air is following the path it does in your simulations.

Also what about the 997 T being so much larger then the Plenum opening? Is this a huge issue?

[Jamesp]

[QUOTE=KRAM36;451898]I don't see where you explained anything? Try me, I'm not afraid to learn.
QUOTE]

Wanting to learn is good! As B2000 pointed out we are discussing fluid flow which brings us to Navier-Stokes. Many years ago I had the pleasure of learning fluid dynamics and aerodynamics which just wouldn't be the same without the good old Navier-Stokes equations. The material isn't completely transparent, so I've included this wiki link to get you started. You'll want to brush up on tensors to get the full impact. Here's the link:

Navier

Now don't say I haven't tried to explain anything to you.

[blue2000s]

Originally Posted by KRAM36

Wow, you haven't posted here in over a year blue2000s. Thanks for the explanation. So what is it about the radius that makes it flow 30% better? Does the larger radius give the air more room to move inside the Distribution T because it's already making it's own natural wedge which would reduce the area for the air to flow?

Yeah, me thinking the engine was making the air pull to the radius looks really stupid, well at least to you guys lol. I never thought about the air creating it's own wedge and I'm trying to figure out why this air is following the path it does in your simulations.

Also what about the 997 T being so much larger then the Plenum opening? Is this a huge issue?

Since finding the truth in lightness , I haven't been back to Porsches, so I don't come around here anymore, but I saw the I was quoted so took the opportunity to chime in.

Air moves by means of a difference in pressure. That's the "voltage". It doesn't matter (mostly) if it's being driven by above atmospheric to atmospheric or atmospheric to below atmospheric. If the difference in pressure is the same, the air would act the same, again mostly.

Moving air has momentum but it's motion is also subject to the pressure (force) acting on it. As air goes around a corner, the air at the inner side of the corner is accelerated more than that at the outer side.

This sets up a pressure difference where the air at the outside pushes on the air at the inside which helps the airflow make a smooth turn around the bend despite the air's momentum trying to push it all straight against the outside of the wall.

There is a point where the effect of the momentum overcomes the pressure difference and the air with the highest momentum (inside of the turn) pulls away from the wall and heads toward the back of the turn. This is called flow separation, you can see it in my CFD pictures.

Separation effectively shrinks the size of the tube that the air is flowing through as the air is ignoring the inside of the turn and really only flowing through some % if the tube. The rest is stagnant air.

The more smooth and large the inner turn, the lower the momentum at the inner wall, and the more likely the airflow at the inner wall is to stay attached. This is why the shape of the inside of a turn has so much more influence on the airflow than the outer. There is some speed threshold at any turn where the flow at the inner wall will detach. That speed depends on the geometry and roughness of the walls. The goal is to design that inner turn so that the threshold is above any speed that the engine will produce.

[blue2000s]

[QUOTE=Jamesp;451945]

Originally Posted by KRAM36

I don't see where you explained anything? Try me, I'm not afraid to learn.
QUOTE]

Wanting to learn is good! As B2000 pointed out we are discussing fluid flow which brings us to Navier-Stokes. Many years ago I had the pleasure of learning fluid dynamics and aerodynamics which just wouldn't be the same without the good old Navier-Stokes equations. The material isn't completely transparent, so I've included this wiki link to get you started. You'll want to brush up on tensors to get the full impact. Here's the link:

Navier

Now don't say I haven't tried to explain anything to you.

The cool thing about the Navier Stokes equation is that it's really just a fluid flow adaptation of F=mA. It all comes back to Newton. Until you go down so the sub atomic level, anyway.

[Jamesp]

[QUOTE=blue2000s;451952]

Originally Posted by Jamesp

The cool thing about the Navier Stokes equation is that it's really just a fluid flow adaptation of F=mA. It all comes back to Newton. Until you go down so the sub atomic level, anyway.

Spoken like a true engineer! I moved away from hard core technical (thermal analysis on the Space Shuttle / systems design) years ago and became a manager (after my spine-ectomy), got fed up with personnel issues, budgets, long hours, and politics and so became a "systems" engineer which means I'm a jack of all trades, and master of none. Mainly work various spacecraft systems issues and project management now. Thanks for the insight on the bend radius.