Topic: Why doesn't anyone make more restrictive Pods?

[Lostboy Steve]

My thoughts;
 Want pods more restrictive.. WET them..
 Everybody knows that KO airboxes flow the best..
 Nearly every bike at Bonneville uses K&N filters.. so yeah , racebike use them successfully.

 My first generation K&N seperate filters  seemed fine, would love to find another set.

 When the K&N rep was hanging out in our pit, I shoulda asked him about pods, I often wondered why they dont make the cylindrical VS the cone shaped anymore..

My uncle had a h1 or h2 back in the day. (I don't remember which one.) When he sold the bike a few years ago he gave me a box of accessories and in the box was an original set of the cylindrical K&N filters. They had to be from the early 70's. All black with the k & N logo on one side.  Anyway, it never road right with them so he took them off. Since then I don't know what I did with them but there were only 3 for the Kawasaki anyway. LOOKING ON THEIR WEBSITE, you may be able to get the round ones still but you'd have to get the measurements. They have a ton of filters and some are small cylindrical ones. JUST IN CASE YOU WANT A SET! 

[cb650]

I read years ago some turbulence is good to keep the fuel atomized.  (where the h&ll did that word come from?)
I dont care I have bikes I run pods and some with original boxes.
I think its funny the seemingly hatred one way or another.
To each his own no matter how stupid.   

[Geeto67]

I read years ago some turbulence is good to keep the fuel atomized. 

I have always heard the same about big American v-8 intakes, never about bikes. It makes sense for a car - a single fuel source feeding 8 cylinders, bigger and longer runners, more vaccum due to the sheer size of the piston, and also the plenum on something like an edlebrock torker II is directly below the carb which means the air and fuel is dumping straight down (easier for it to seperate out). On a cb we have individual carbs for individual cylinders and the draw is a side draft not down draft like on a chevy 350. Plus the amount of fuel we are talking about is very small to be effective and with a side draft setup it is better to have high velocity than turbulence since you are dropping the fuel into the air stream 90 degrees from the direction of flow.

[cavi]

http://www.cyclexchange.net/Craig%20Filter%202.JPG

What about this filter setup from CycleX sems like it would be a good compromise?

[TwoTired]

http://www.cyclexchange.net/Craig%20Filter%202.JPG

What about this filter setup from CycleX sems like it would be a good compromise?

A picture of the outside only?
What does it look like on the inside where all the flow engineering has importance?

Do they give a specification for the pressure drop that filter drop presents to the carb throat.
Do they give an effective membrane surface area specification?
Do those couplers present a match to the internal throat diameter of the carb they are place upon?
What center to center spacing do the carb couplers have?

Then there is the water ingress/contamination that's typically encountered on a working functional bike.

I recall during my design career, marketing and sales department always wanted a mock up of our new products well before the engineering was completed (sometimes not even started) on the inside components.  It always seemed odd, somewhat humorous, to me to see a pretty picture of a unit, complete with glowing lights, that I knew had no guts to actually perform any other useful function, than be camera proud.

Part of my job at times, was to test products we would purchase to resell, just to verify or determine if they met their design specifications.
It wasn't very often they did with a revision A of the offering.

However, if the only criteria for a product is that it looks pleasing, can what it is inside the facade be anything other than an afterthought?

[Duke McDukiedook]

http://www.cyclexchange.net/Craig%20Filter%202.JPG

What about this filter setup from CycleX sems like it would be a good compromise?

Compromise indeed.

[TwoTired]

I read years ago some turbulence is good to keep the fuel atomized. 

Turbulence can be compared to bullet placement, in that it is critical as to where exactly it is placed, friend or foe. 
Further, I'm pretty sure you are using that quoted catchphrase out of context.

Turbulence is air speed dependent.  See the flag wave?  That is turbulence of the air around the flag pole.  Does the flag always wave?  No.  Are there always the same number of "waves" that you see along the length of the flag?  That is the frequency length of the turbulence related to air speed.

If MPG is the main parameter/goal, turbulence downstream of the atomizing device (carburetor) can improve atomization and a more complete burn of the fuel with a certain air speed range.  However, since turbulence has a limiting effect (drag) on air flow, it can diminish the volume of air that can be passed at higher air speeds.  So, what is good for MPG at lower speeds, can effectively limit maximum peak power availability.  You want higher MPG or higher peak HP?

Now place that turbulence upstream of the carburetor, and that same turbulence can either increase or decrease carb jet flow in a modal pattern that varies with air speed.

If you freeze that waving flag mid-wave, you will see portions of the flag on the right side of the pole and some on the left side of the pole.  This is visual proof that within turbulence there is alternating high an low pressures present downstream of the flag pole.  The flag pole is the turbulence inducing device.  You do NOT want those high and low pressure waves traveling over the exit ports of the fuel jets inside the carburetor throat.  Those waves will change with air speed in both magnitude and wave length, making jet orifice selection a compromise, at best.  If you can't predict what the pressure differential is applied across the jet tube orifice in the carb, you can't predict the flow of any given size jet.  All you can do is react to what occurs, make a guess, and adjust accordingly, to give the best results at the throttle position of interest.

Duct physics does not go away just because you removed a lot of the duct.  It only changes the parameters involved.

[KJ790]

I read years ago some turbulence is good to keep the fuel atomized. 

Turbulence can be compared to bullet placement, in that it is critical as to where exactly it is placed, friend or foe. 
Further, I'm pretty sure you are using that quoted catchphrase out of context.

Turbulence is air speed dependent.  See the flag wave?  That is turbulence of the air around the flag pole.  Does the flag always wave?  No.  Are there always the same number of "waves" that you see along the length of the flag?  That is the frequency length of the turbulence related to air speed.

If MPG is the main parameter/goal, turbulence downstream of the atomizing device (carburetor) can improve atomization and a more complete burn of the fuel with a certain air speed range.  However, since turbulence has a limiting effect (drag) on air flow, it can diminish the volume of air that can be passed at higher air speeds.  So, what is good for MPG at lower speeds, can effectively limit maximum peak power availability.  You want higher MPG or higher peak HP?

Now place that turbulence upstream of the carburetor, and that same turbulence can either increase or decrease carb jet flow in a modal pattern that varies with air speed.

If you freeze that waving flag mid-wave, you will see portions of the flag on the right side of the pole and some on the left side of the pole.  This is visual proof that within turbulence there is alternating high an low pressures present downstream of the flag pole.  The flag pole is the turbulence inducing device.  You do NOT want those high and low pressure waves traveling over the exit ports of the fuel jets inside the carburetor throat.  Those waves will change with air speed in both magnitude and wave length, making jet orifice selection a compromise, at best.  If you can't predict what the pressure differential is applied across the jet tube orifice in the carb, you can't predict the flow of any given size jet.  All you can do is react to what occurs, make a guess, and adjust accordingly, to give the best results at the throttle position of interest.

Duct physics does not go away just because you removed a lot of the duct.  It only changes the parameters involved.

You want a turbulent boundary layer in a port, not turbulence. These are two distinct things. If your intake port is going turbulent then your port will essentially choke and your power will drop off like a rock. If you have a turbulent boundary layer with otherwise laminar flow in a port then you will flow more air and will not have beads of fuel collecting on the port runner which can cause running issues.

[Geeto67]

http://www.cyclexchange.net/Craig%20Filter%202.JPG

What about this filter setup from CycleX sems like it would be a good compromise?

Compromise indeed.

Assuming it uses the factory carb to airbox rubbers, it is a step in the right direction and certainly better than crappy pod filters.

[Blitzburgh207]

They are a performance item when used WOT and tuned for RACING, they just suck ass when used in street applications.

"Street applications" is sort of subjective... What about those of us at WOT all the damn time?

[TwoTired]

You want a turbulent boundary layer in a port, not turbulence. These are two distinct things. If your intake port is going turbulent then your port will essentially choke and your power will drop off like a rock. If you have a turbulent boundary layer with otherwise laminar flow in a port then you will flow more air and will not have beads of fuel collecting on the port runner which can cause running issues.

This is a side issue for the SOHC4, as the ports are not made larger to allow for a boundary layer of non-essential turbulent air.  Again, context is important.  I don't disagree with what you forward.  I just don't see how it applies to the SOHC4.  It's a matter of turbulence placement, which the SOHC4 was not designed to incorporate.

Further, in the context of this thread, pods generate turbulence at the carb intake mouth.  The aftereffects of this turbulence reach into the carb throat and effect the fuel delivery ports.  Boundary layer turbulence at that placement is not going to help much of anything, imo.

Cheers,

[KJ790]

You want a turbulent boundary layer in a port, not turbulence. These are two distinct things. If your intake port is going turbulent then your port will essentially choke and your power will drop off like a rock. If you have a turbulent boundary layer with otherwise laminar flow in a port then you will flow more air and will not have beads of fuel collecting on the port runner which can cause running issues.

This is a side issue for the SOHC4, as the ports are not made larger to allow for a boundary layer of non-essential turbulent air.  Again, context is important.  I don't disagree with what you forward.  I just don't see how it applies to the SOHC4.  It's a matter of turbulence placement, which the SOHC4 was not designed to incorporate.

Further, in the context of this thread, pods generate turbulence at the carb intake mouth.  The aftereffects of this turbulence reach into the carb throat and effect the fuel delivery ports.  Boundary layer turbulence at that placement is not going to help much of anything, imo.

Cheers,

Boundary layers come into play whenever a fluid is moving over a surface, and play a huge role in ports of any size. SOHC4 ports are no different.

To say that pods create turbulence throughout the entire port is sort of a blanket statement that I do not agree with completely. It depends on how the pod is designed, and it is not necessarily true with all pods. Reynolds numbers in an intake port can get pretty high when the valve is nearing fully open. In pretty much every engine the flow will go into the transitional stage if not fully turbulent due to the Reynolds number reached (nothing to do with what is upstream of the port). This gets worse as RPM's increase, hence why volumetric efficiency drops after a certain RPM and your power will drop off. Keeping a turbulent boundary layer in the port runner is important at lower RPM's and lower valve lifts (valve partially open) while the flow may be laminar or transitional. This can help increase the volumetric efficiency while decreasing the chance that fuel will bead on the port wall.

IMO the biggest problem with some pods are the pressure pulses that can occur outside of the pod while the bike is at speed. Von Karman vortices being shed off of the engine and frame around the pod can create pressure pulses around the pod that can affect the performance of the engine. There are ways of creating shields around the pods to help with this. The other problem sometimes faced is the change in effective port runner length due to how some pods are made. This will affect the power output of an engine at different RPM's, for better or worse depending on the engine and what the builder is looking for.

[TwoTired]

To say that pods create turbulence throughout the entire port is sort of a blanket statement that I do not agree with completely.

I never said that.  I said that introducing turbulence at the carb's entrance mouth has effects that reach into the carb throat, with specific impact on the pressure presented to the fuel jet exit ports.

It depends on how the pod is designed, and it is not necessarily true with all pods.

If the filter media base material structure is formed into aerodynamic shapes and aligned with the air flow direction, the turbulence can be minimized.
You know of any pods that have aerodynamic filter media structure?
Place an obstruction into a path of air flow, and turbulence extends outward from the lee side.  See pic below for an example.

Have you seen the K&N air flow test bench?  See pic 2 below.
Note the test filter at the end of a 6 ft tube, which places the flow measurement devices well beyond the reach of turbulence induced by the filter membrane.  The stock air box does this in a limited way by moving the filter membrane source of turbulence farther from the carb throat entrance and placing an alignment funnel onto the carb entrance mouth.   See Carb FAQ.
I don't believe there is ANY pod filter design available that can solve this fundamental issue.

IMO the biggest problem with some pods are the pressure pulses that can occur outside of the pod while the bike is at speed. Von Karman vortices being shed off of the engine and frame around the pod can create pressure pulses around the pod that can affect the performance of the engine.

I've included a pic for the reader to see what Karman wake turbulence looks like.
These pics can also be found in the Carb FAQ, from a posted discussion that occurred 2 years ago on this forum.
http://forums.sohc4.net/index.php?topic=5410.msg741438#msg741438

[Pinhead]

You want a turbulent boundary layer in a port, not turbulence. These are two distinct things. If your intake port is going turbulent then your port will essentially choke and your power will drop off like a rock. If you have a turbulent boundary layer with otherwise laminar flow in a port then you will flow more air and will not have beads of fuel collecting on the port runner which can cause running issues.

This is a side issue for the SOHC4, as the ports are not made larger to allow for a boundary layer of non-essential turbulent air.  Again, context is important.  I don't disagree with what you forward.  I just don't see how it applies to the SOHC4.  It's a matter of turbulence placement, which the SOHC4 was not designed to incorporate.

Further, in the context of this thread, pods generate turbulence at the carb intake mouth.  The aftereffects of this turbulence reach into the carb throat and effect the fuel delivery ports.  Boundary layer turbulence at that placement is not going to help much of anything, imo.

Cheers,

Boundary layers come into play whenever a fluid is moving over a surface, and play a huge role in ports of any size. SOHC4 ports are no different.

To say that pods create turbulence throughout the entire port is sort of a blanket statement that I do not agree with completely. It depends on how the pod is designed, and it is not necessarily true with all pods. Reynolds numbers in an intake port can get pretty high when the valve is nearing fully open. In pretty much every engine the flow will go into the transitional stage if not fully turbulent due to the Reynolds number reached (nothing to do with what is upstream of the port). This gets worse as RPM's increase, hence why volumetric efficiency drops after a certain RPM and your power will drop off. Keeping a turbulent boundary layer in the port runner is important at lower RPM's and lower valve lifts (valve partially open) while the flow may be laminar or transitional. This can help increase the volumetric efficiency while decreasing the chance that fuel will bead on the port wall.

IMO the biggest problem with some pods are the pressure pulses that can occur outside of the pod while the bike is at speed. Von Karman vortices being shed off of the engine and frame around the pod can create pressure pulses around the pod that can affect the performance of the engine. There are ways of creating shields around the pods to help with this. The other problem sometimes faced is the change in effective port runner length due to how some pods are made. This will affect the power output of an engine at different RPM's, for better or worse depending on the engine and what the builder is looking for.

This. The SOHC4 ports can be easily modified to take advantage of boundary layer turbulence to reduce "wet flow" on the intake port wall...

Surface Turbulence