Intake Manifold Design

before one can calculate for a plenum, first one needs to decypher what constitutes the plenum?
is it all of the intake tract up to the actual port/intake valve, including the other ports not in cycle, or is it only part of the intake system?
If one were to use the Hamilton example, I would say all of it from the turbo to the intake valve - in which case it would be on the order of some 3.5 times too large as a plenum
 
seeker1056 said:
before one can calculate for a plenum, first one needs to decypher what constitutes the plenum?
is it all of the intake tract up to the actual port/intake valve, including the other ports not in cycle, or is it only part of the intake system?
If one were to use the Hamilton example, I would say all of it from the turbo to the intake valve - in which case it would be on the order of some 3.5 times too large as a plenum
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Regarding the rail manifold, the plenum def includes the runner volume to the valves, but it is as of yet undetermined whether the total volume from the turbos on will act as the effective volume or if the second end tank after the last intake pressure drop across the IC core will act as the effective volume. It is possible that once the plenum volume reaches a certain size the runners will behave as if they are open to atmosphere. I am looking forward to the subsequent testing throughout the system and data being recorded and analyzed. Since diesels typically run lower rpms as compared to the gas setups, a larger plenum may benefit a diesel intake since, in the behavior of a spring-mass system, the "mass" is the larger volume between runners. A larger mass on the same size and strength spring will resonate at a lower frequency. I keep seeing "1.5" times engine displacement cropping up, but have seen no research explaining this...only people suggesting it as a rule of thumb. Anyone know where this "rule" came from? Anyone know why it's ok, and if it does apply to gas engines, why it must also pertain to diesel applications as well? I'm aware that mathematically this can be calculated using an equivalent LC circuit, and is the first place I will go when the Beta design begins. NO ONE TAKE THIS THE WRONG WAY, but please do not begin replies with words like "think", believe", "heard", "imagine" etc. Those words are an immediate marker that indicate the rest of the post is probably not based on science fact. Please cite ALL sources.
 
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Plenum in my view should simulate an atmosphere. Sizing of the plenum should be relative to purpose and the runners size we can view in more than one way. Volume or CFM which will create two views amongst tuning. When I spoke to Darin Morgan a few years ago on intake manifolds he mentioned that we must incorporate the load of the engine along with designing the runners to have more flow than the actual port in the head to flow not the same because the point of restriction will be present where we don't need it. Since we have a control in the tuned venturi area and bowl area with the least amount of flow control closer to the port opening in the head as long as the EFA from the manifold transitions from the intake to the runner of the head our flow should be fine. I Believe, yes Child9, this portion of what Darin mentioned to me could very well be brought over to DI diesel engine operation but its just my honest view here.

As far as rectangular versus circle ports, I am at a stand still as far as how the waves react within either because you can have one of each port that flow the same but have different volumes.
 
I would say all of it from the turbo to the intake valve - in which case it would be on the order of some 3.5 times too large as a plenum
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If we incoporate the entire route, which we need to view anyhow, if there is an A2A in the system that is maybe too big, just simply adds to volume we must pressurize therefore in addition creates a bigger lag. If we can reduce the over-all volume we can cut down on lag time. However the flow must be cooled; if the A2W version can support higher heat transfer from the induction charge how much space (internal intake system) do we really need?

As far as including the intake system from the turbo to the plenum, its more of a delvery system than a plenum because you don't have cylinders pulsing on this area you have a kinetic energy situation going into a pressure energy then a pressure energy going back to a kinetic energy movement once the valve opens enough for flow to occur once our reversion action has began to reside, that is if our cylinder pressure has blown down enough upon early exhausting lobe lift to allow the intake to become pulled through overlap or simply overpower the exhaust within the cylinder due to pressure difference.

I see it as two parts. Turbo to plenum - delivery system, Plenum to cylinder - the residing supply of air to feed the 1,200 intake pulsations or whatever your engine speed may be.
 
Would anyone have the on-center measurement from end to end of the Cummins 12 valve intake ports? Maybe a port height too?
 
all of the valves are 120mm apart so 6 x 120 centreline to centreline

port height where do you want to measure - at the valve, or at the choke point, or at the face of a cut off intake - which varies considerably due to casting/core shift, or at the outlet of the cast plenum
 
child9 said:
Yes. The 5 other runners that all go to closed intake valves are considered part of the plenum volume at that point, since all they are doing is contributing to the plenum volume while the wave action we are concerned with is moving through the 6th runner with the open intake valve.
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Pulses are bouncing back and forth inside the other 5 runners so I don't believe they should be added to plenum volume.
 
Ok, I was just asking about the head entrance at the mating flange for the intake manifold as far as port height.
 
Leiffi said:
Pulses are bouncing back and forth inside the other 5 runners so I don't believe they should be added to plenum volume.
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Big picture, yes...but we are talking about one wave and it's reflection. Only one cylinder's intake valve(s) event happens at a time...and the speed of sound in gas that hot is really fast...or you could read the ASME document that Zach pointed out. It says that runner volume is calculated into total plenum volume. I believe that.
 
Still have been trying to find some time to get my scanner in gear but its taking to darn long or I would have a picture up to have everyone critique. Anyone have any headway on something of their view?
 
Would anyone like to put an accurate definition explaining why a 2nd order, 3rd or 4th order wave is labeled the way it is?
 
Not sure I understand what you mean. If you are not clear on the difference between a first (fundamental), second, or third order wave then check this out:

http://www.physics247.com/physics-tutorial/images/harmonics1.GIF

Any specific resonant frequency requires a specific length of tubing based on the inner cross sectional area of the tubing. First order freq that is in the rpm range is usually VERY long for most applications, so we have to settle for second or usually 3rd order wave. 2nd order is the fundamental divided by 2, 3rd is the fundamental divided by 3...etc. The "gain" from wave tuning is highest at the fundamental, but in the motorsports world we tend to be forced to settle for the second or more often 3rd harmonic in order to get a runner length that fits our applications. In the case of Zach's intake I didn't have to worry about physical constraints or packaging, so it is a different (and FREEING situation). In the case of a truck engine bay, there are many more physical constraints, obviously.
 
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I understand that, but, just saying the 2nd order doesn't seem to be the whole picture explaining the reasoning behind why the wave is the way it is. 1st order should travel and reflect twice at the open end in the plenum Edit: reflects once off the closed valve after the valve closes and end up at the valve when its opened correct, from how I am understanding it.
 
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Yes, but the goal is to get a standing wave at the desired frequency to fit...thus placing a low pressure area (node equivalent) at the valve when it opens.

I realize that the drawing presented is an illustration of a transverse wave and not a compression wave, but fundamentally they are the same. High pressure areas are where the anti-nodes are, low pressures are where the nodes are.
 
This low pressure we are providing the last bit of ramming presented by the charge motion correct?

From what all I have read and been told the waves (acoustical) travel with (positive) AND against (negative) our actual flowing air, assisting our flow to fill the cylinder regardless of the actual acoustical wave direction, once a change in CSA happens, can/will change our wave travel and looked like after the closed valve creates the wave, as the wave progress' regardless of the runner length our wave speed and probably amplitude (Child9? am I thinking in the correct nature) as well begins to degrade or slow in speed.

Would we like to have this low pressure position at the valve bowl or would we want it to end up in the cylinder?

If we have the valve close, I am told this creates a positive pressure wave up to the plenum, as it reflects the plenum then we have a suction wave that reflects off the closed valve and back as a suction wave to the plenum opening and which positive wave starts and ends at the open valve and fills the cylinder.

For those reading it looks to be our waves label's are as follows.
1st order - explained above
2nd order - reflects TWICE at the closed valve
3rd order - reflects THREE times " "
4th order - reflects FOUR times " "

Each order will have a shorter runner length no matter what. One good example of a 1st order tune would be the old Chrysler Cross-ram manifold. Its starting to catch on quicker everyday! I am still trying to fix my printer/scanner, I might just take a picture of my drawing and post it. Pain in the rear. Much more to learn, yes indeed.
 
In the case of a truck engine bay, there are many more physical constraints, obviously.
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A street driven truck yes, a puller and OTR hauler there is a little more room.

I was thinking on the size of the bowls in our heads being smaller in size. Since a wave can change because of a change in CSA, with the smaller intake bowls the wave is not harmed as much as if the bowl or any CSA change is drastic. Of course we can not forget the temperature and gas composition.
 
I don't think the Chrysler setup was able to take advantage of the first wave. They can't do that in NASCAR even. What is the length required for first wave at 6000 rpm? I think it's something like 30+ inches.

On the exhaust side you want a low pressure wave to be at the valve as it opens to assist pulling exhaust gasses out, and in the case of overlap, assist with new air being "sucked" in. On the intake side you want a high pressure wave at the valve so it is pushing in. THe two combined push and pull a lot more molecules into the combustion chamber netting more power.

As far as positive and negative waves go, they both exist and both travel both with and against the air flow. "Positive" simply refers to a high pressure or amplitude, while the "negative" wave is the low pressure part. A high pressure is immediately followed by a low pressure moving in the same direction. Once everything is in resonance the waves appear to be "standing"...like looking at a spinning wheel through a video camera. It can look like it is still, though it is not.

"For those reading it looks to be our waves label's are as follows.
1st order - explained above
2nd order - reflects TWICE at the closed valve
3rd order - reflects THREE times " "
4th order - reflects FOUR times " " "

Sort of. The order or harmonic is how many high and low areas fit in the runner length. The more nodes you have to fit in the tube the weaker the overall affect is. By choosing a different harmonic we are simply syncing the valve events with whatever harmonic of the fundamental wavelength we can...given the physical constraints of the application and the resonant frequency desired.
 
Yeah I am not sure if that old Chrysler did or did not harness it completely, one long intake though!

If we use IMO positive and negative without pressure following either one I see it as a directional not as pressure, if I see positive or negative pressure such as a compression or suction I see it as what you describe the node or "anit-node". Since we mention these again we have to bring up a rarefaction which follows the compression wave which is the other half of the wave decompressing as it moves along.
 
Fahlin Racing said:
If we use IMO positive and negative without pressure following either one I see it as a directional not as pressure, if I see positive or negative pressure such as a compression or suction I see it as what you describe the node or "anit-node". Since we mention these again we have to bring up a rarefaction which follows the compression wave which is the other half of the wave decompressing as it moves along.
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I'm sorry man, I don't understand this. Direction doesn't really matter, all that does matter is whether it is a high or low pressure area that is being experienced at the valve in question when it opens. As far as nodes and anti-nodes go, it's not what "I" call them. A node is the high point of a transverse wave or the high pressure area of a compression wave, and an anti-node is the middle or low pressure area. I did not name them. :)

Rarefaction is usually in reference to the "spread" of a wave, like a wave on the ocean. In that context that doesn't apply since we are channeling a wave down a tube and therefore not allowing it to spread. If you mean the low pressure that follows the high pressure (most likely), then yes, that is there...but man it is all moving so fast...literally faster than the speed of sound in "normal" temp air. Super fast. This is why we have difficulty taking advantage of the "first" wave. It's gone down the runner and back WAY before it can open again unless you can manage 18,000 rpm or something. Actually you touched on this earlier. This is where the number of reflections come in and that the subsequent reflections are weaker, though I hesitate to relate that to "harmonics" specifically.

In the end we are fortunate to have a valve open in an exhaust manifold just after the moment the 3rd reflection of the wave created from the last time that valve in question slammed shut. It will happen, but getting it to happen at the specified rpm for our application is the tricky part.

I'm sorry to all of you legit guys on here. Please don't take this the wrong way. I'm not pious or prideful or thinking I'm better than anyone... but I think I'm out of here. Overall I find this specific forum (and I'm on a LOT of different forums) so full of crap talkers that real info is rare (seems like every useful thread gets mucked up by two keyboard racers)...besides my latest diesel intake project with Zach (who is no longer a sponsor?) is complete sans testing so until I build a turbo diesel scooter for my wife, I no longer have any vested interest in diesels, unfortunately. As a gasser, I am enamored with the diesels. No TB and the block being the limit for boost? Crazy high compression ratios??? I freakin' love it! Ahhhh well. If any of you are local to Austin Texas and need some fab work done, I may be able to help. chad.kassem@fringexvo.com.

Good luck everyone, and thanks for the engaging conversation Fahlin.

Peace.
 
Thanks for the insight Child9, I appreciate it and I am sure others interested are too. Good luck with your venture!

I however will state, again, the direction of travel you should still DISTINGUISH a positve direction and negative direction even if there may be little importance Child9, but its a part of the fundemental understanding of the engine like you mentioned earlier, must be covered top to bottom. Either way the acoustical wave travels it helps our positive (towards the engine) directional flow regardless of high pressure or low pressure positions throughout the flow path. I realize as well, you didn't name them bud, just used them in the conversation is all.

One thing I have come across recently is this quote,

A pressure wave travels at the speed of sound plus the speed of the moving air particles
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