Flow concerns regarding intake Plenums

[Powerstroked162]

Lets try and follow along here.... That's exactly what I just said in my original post..

Fact of the matter is that our stock heads flow like crap. Before anyone goes about making flow gains with different plenums, the heads need to be addressed first

LOL I don't even know why I bothered to help

 

[ToMang07]

I installed the reinforcing inserts about 2 years ago or more... Run T bolts without springs and crank them down tight. Never blown a boot there, only at the turbo and thats at over 50psi...

Dont see a need to change something thats not broken.

Glad I'm not the only one. :doh:

 

[OSCS]

LOL I don't even know why I bothered to help

Mearly stating that you repeated exactly what I said " I don't think it makes one bit of a difference"

 

[Worstenemy453]

Plenum

I don't see the argument here. Upgrading your plenum size isnt going to make more air go into the heads. Your turbo pushes air. The air HAS to go somewhere. Unless the air reaches a restriction so great that it can overcome the force of exhaust gasses compressing the incoming air, then no air will stall until it gets to the head and then the valves. The only difference I see in the plenum designs (stock vs larger) is the pressure at which the air enters the head.

Example: flow 300cfm through a 1" diameter tube. It will flow at X psi. Flow the same 300cfm air through 2" diameter tube and it will flow at X/2 psi. No less air flowed, only at a different pressure between two points.

That's not to say I don't like the Riffraff plenums (I assume there are others, just haven't looked), I just don't think flow has anything to do with it. Just like how changing your rear diff oil to synthetic will improve MPGs.. To me the pluses of these aftermarket products is looks, quality, and strength.


Sent from my iPhone

There is no argument. No one is trying to make one. There is only facts. The stock plenum will flow more than the head needs, therefore heads should be addressed first. The un named inserts would be the best route to go for improving boot reliability and then the heads would be the first route to start going after performance.

Lets try and follow along here.... That's exactly what I just said in my original post..

Fact of the matter is that our stock heads flow like crap. Before anyone goes about making flow gains with different plenums, the heads need to be addressed first

Exactly how i feel.

 

[Charles]

Plenum

I don't see the argument here. Upgrading your plenum size isnt going to make more air go into the heads.

It could. If the volume of the plenum is only roughly that of a single cylinder's displacement, then each time one cylinder's intake valve opens there would be a sizable drop in the pressure of the manifold. When the intake valve closed again the pressure would spike up high. Depending on firing order and cylinder layout, certain cylinders would get air during a spike, while others got air during a lull in pressure, leading to reduced power through uneven contribution.

A larger plenum volume would dampen the pressure fluctuations and give more uniform distribution to each cylinder.

Your turbo pushes air. The air HAS to go somewhere. Unless the air reaches a restriction so great that it can overcome the force of exhaust gasses compressing the incoming air, then no air will stall until it gets to the head and then the valves. The only difference I see in the plenum designs (stock vs larger) is the pressure at which the air enters the head.

The turbo doesn't change the airflow. At 5psi there is exactly the same CFM moving through the intake and heads as at 500psi.

This is why higher flow rates for heads, intakes and valves apply equally to NA and forced induction engines. The concepts of runner length, shape size also hold the same effects. The only way to increase CFM flow is through these things. Turbocharging only increases the weight of each CFM, not how many pass through the engine every two revs.

The concepts behind plenum volume requirements for an NA engine hold just as true for forced induction engines. The forced induction engine is required to flow fewer CFM than the NA engine, due to higher density of each of those cubic feet, but the effects of intake charge velocity, timing and dampening fluctuations are all working just the same forced induction as NA. It's like you drive an NA car down to death valley, vs the top of Mt. Everest. At death valley you'd be forced induction in comparison. In neither case does the engine move more or less CFM, but because the air is much denser in death valley, it sure makes more power with those CFM.

Example: flow 300cfm through a 1" diameter tube. It will flow at X psi. Flow the same 300cfm air through 2" diameter tube and it will flow at X/2 psi. No less air flowed, only at a different pressure between two points.

Although a 2" diameter line is actually much more than twice the flowable area of a 1" line, I see what you're getting at, and yes, the same flow through a reduced restriction requires less pressure. Well, if your intake runners are ____ square inches in section, and the pressure in the manifold is fluctuating wildly because the plenum is insufficiently sized to handle the demands, then some cylinders will receive _____psi while others might receive much less. The ones receiving much less pressure will also fill less. And even as each single cylinder opens the plenum pressure will drop, so that even just by the end of each cylinder's intake stroke the pressure will be lower than average by a meaningful amount. In this case all cylinders have reduced filling.

The turbo has nothing to do with that.

That's not to say I don't like the Riffraff plenums (I assume there are others, just haven't looked), I just don't think flow has anything to do with it. Just like how changing your rear diff oil to synthetic will improve MPGs.. To me the pluses of these aftermarket products is looks, quality, and strength.


Sent from my iPhone

On Edit:

Going from the stock superduty intake plenum to the Van intake plenum that is MUCH smaller in volume, my boost gauge fluctuation quadrupled. From minor shaky movement to 5+ psi movement.

Now bare in mind, this is at the end of an 1/8th" signal line all the way up in the cab, on a gauge that is at least somewhat dampened itself. The fluctuations occurring right at the heads is probably insane.

The plenum needs to ideally be 2 or 3 times the displacement of a single cylinder. That will handle the fluctuations nicely, which I plan to do as soon as I rid my valley of a turbo.

 

[TARM]

The only way you are getting more perf form the intakes is if a system was made that actually diverted the air in such a way as to have equal flow into all cylinders. The other thing that would offer benefit is increase the volume/length of the air column going into each cylinder. The only way the later is going to happen is with a tube intake setup and to fit that under a standard hood would be some work. So when it comes down to looking at the various plenums etc I do believe big power has been made with the various designs. so the difference in perf is at the very least negligible. These are not naturally aspirated engine here. That is at least the conclusion I reached about this things.

 

[Worstenemy453]

Even though there is no room, i wonder if a spyder'd intake manifold set-up would work if the turbo was relocated.

Also just getting back to the roots, an engine is an air pump, it takes air in and pushes it out. The more free flowing that this can be achieved the more efficient and powerful it will be. The turbo just masks the poor head flow IMO.

 

[Big Bore]

As usual, Charles explained it, and still people don't get it. Oh well.

Available volume of compressed air. Very simple concept. Just like your air tools and compressor. Available volume of compressed air.

My one complaint about my beans billet intakes is how hard it is to get the boots and spyder on. Big deal.

Also, color me skeptical about the new o-ring units. For a race motor that might need to be disassembled/reassembled for whatever reason, they might have an advantage, but with reduced volume over stock?

 

[Worstenemy453]

As usual, Charles explained it, and still people don't get it. Oh well.

Available volume of compressed air. Very simple concept. Just like your air tools and compressor. Available volume of compressed air.

My one complaint about my beans billet intakes is how hard it is to get the boots and spyder on. Big deal.

Also, color me skeptical about the new o-ring units. For a race motor that might need to be disassembled/reassembled for whatever reason, they might have an advantage, but with reduced volume over stock?

LOL True.

 

[Tom S]

Who are you two saying does not get it?

 

[Charles]

As usual, Charles explained it, and still people don't get it. Oh well.

Available volume of compressed air. Very simple concept. Just like your air tools and compressor. Available volume of compressed air.

My one complaint about my beans billet intakes is how hard it is to get the boots and spyder on. Big deal.

Also, color me skeptical about the new o-ring units. For a race motor that might need to be disassembled/reassembled for whatever reason, they might have an advantage, but with reduced volume over stock?

I machined the lip on ******s down to like 0.0625" or so IIRC. If it was 0.125 I made it 0.0625, or if it was 0.250 I made it 0.125. I cut it in half basically.

I machined receiver grooves in the flange to allow the I-Gray to form a mechanical lock between bolts too. I don't know that any of it was necessary, but it was simple and quick to do, while installing them again would be a PITA in comparison.

 

[Big Bore]

Who are you two saying does not get it?

The ones saying not to worry about the intake volume/flow because the heads only flow so much.

 

[Ron's Power Stroke]

Fluorocarbon (Viton®) o-rings have an unlimited shelf life. The materials used in fabricating o-rings varies and that can lead to them lasting or not. If you are worried about them degrading you should also worry about the ones in the pedestal and turbo flanges. Those are standard AS568 Viton o-rings and they can fail too. Any seal has the opportunity to degrade over time, even the RTV That is used to seal the OEM or aftermarket plenums can and does breakdown over time. I was pretty shocked at how easy my plenums were to remove with very little surface cleaning required on the head when I installed billet plenums.

O-rings are normally used anywhere there is a machined part interface where the part fits as close to perfect as it can. RTV is normally used where you have inferior part interface, like the OEM plenums, oil pans and such. Stamped steel does not provide the near perfect surface that machined parts do. Neither does cast aluminum unless it is machined afterwards. That is the biggest reason that o-rings can be used in this application over RTV that makes a mess. If you are a die-hard RTV fan, you could always remove the o-ring and then the o-ring groove machined into the plenum would make a nice channel for the RTV to squeeze into making a good seal too.

Quote
(Viton®) o-rings have an unlimited shelf life.

you are correct..I put the fuel bowl and the feed lines on the shelf 5 years ago and them orings still don't leek...its to bad there shelf life ends when you put them on a motor and bake them a few times.. also doesn't work out well making them work in -20* weather....

quote
If you are worried about them degrading you should also worry about the ones in the pedestal and turbo flanges.

don't need to worry about them..I tossed them out already...

quote
The materials used in fabricating o-rings varies and that can lead to them lasting or not.

that is my point...RTV works 99.9% of the time for life...so for 100 bucks more, not only do I get a good clamping point..but all 8 of my cylinders are getting all the air any part out there at this time can give me plus I don't have to worry about ever getting in there again to replace a 50 cent oring..RTV isn't messy...its the installer...do a little cleaning when you put things back together..it only take a couple minutes...

 

[OSCS]

As usual, Charles explained it, and still people don't get it. Oh well.

Available volume of compressed air. Very simple concept. Just like your air tools and compressor. Available volume of compressed air.

My one complaint about my beans billet intakes is how hard it is to get the boots and spyder on. Big deal.

Also, color me skeptical about the new o-ring units. For a race motor that might need to be disassembled/reassembled for whatever reason, they might have an advantage, but with reduced volume over stock?

Who said anything about RR plenums flowing less than stock?

 

[Ron's Power Stroke]

As usual, Charles explained it, and still people don't get it. Oh well.

Available volume of compressed air. Very simple concept. Just like your air tools and compressor. Available volume of compressed air.

My one complaint about my beans billet intakes is how hard it is to get the boots and spyder on. Big deal.

Also, color me skeptical about the new o-ring units. For a race motor that might need to be disassembled/reassembled for whatever reason, they might have an advantage, but with reduced volume over stock?

Who said anything about RR plenums flowing less than stock?

read it again..

 

[Big Bore]

Who said anything about RR plenums flowing less than stock?

No one. Internal Volume.

 

[Big Bore]

read it again..

Beat me to it. LOL

 

[Powerstroked162]

No one. Internal Volume.

It doesn't change performance one bit. Been tested. Been proven. Many, many, many years ago when this crap mattered. Good for riff raff and their new design. I hope they come up with regulated returns and boost foolers to go with it

 

[OSCS]

I see what charles is getting at now. Only solution i see to the plenum issue is no plenums at all.. Some one needs to design an actual intake manifold to equally deliver airflow over each cylinder. I realize this would be hard to do with a turbo in the way but with one designed and some head work I think it would yield some nice results

 

[Big Bore]

It doesn't change performance one bit. Been tested. Been proven. Many, many, many years ago when this crap mattered. Good for riff raff and their new design. I hope they come up with regulated returns and boost foolers to go with it