1. You have to pull the cam to get the actual housing off. I wouldn't want to machine/weld with the housing still bolted to the engine. It is definitely an option though that I will keep in mind.

2. In the picture I posted it looks a lot better than it is, but the factory plenum is very restrictive and that is the main reason it gets machined off. That and machining it off allows access to be able to port the intake runners. I don't think over 5X the factory horsepower was ever even considered when they were originally designed lol. Out of curiosity, why do you think the ship has sailed in terms of being able to fabricate a plenum only style manifold? The way I see it, I have a better starting point now than just building a box onto the already restrictive factory plenum. I feel like, even if it isn't perfect, it will be significantly better than what the factory one was. I posted on here because I wanted input from others so if I come across like I am discrediting what you're saying or anything, that is not the intent and I apologize.

I have two designs that I have been working on for a plenum only style, side inlet (technically the front of the motor) and a middle inlet that I more or less just started. Both of them would have an open flange where it connects to the head. For the side inlet I was trying to use some of the port angles as guides for the design but the more I mess with it, I don't think I will be able to angle the inlet enough to evenly distribute the air (or at least somewhat evenly) without a bunch of extra bends right at the entrance of it.
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I was looking more at how it was all sitting in the engine bay last night while having a few beers, and thought I might be able to do a center inlet style and go up and over the injection pump as long as I kept it fairly close to the pump. It still will require some bends and whatnot but I think having the inlet centrally located will help with air distribution, even if the ports in the head are angled towards the front. This style should also allow me to make the plenum bigger too and possibly allow me to send the air straight into a flat wall if I change the entrance angles around (as long as I can fit it under the hood still.

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Well ~ I'm not there to see it firsthand, BUT.....it doesn't look that restrictive to me, since it's completely open surrounding the ports, except for the top over the R/H (front) end. And, that portion of the plenum ("shelf") roof could be cut out (even clear to the end, past the angled sealing rib ~ then a new end-rib could be added with A+B epoxy putty).

After which, I envision a pyramid-shaped plenum bolted thereon with a side entry at the top of the "pyramid". The side entry would require the incoming charge air to smack into the opposite wall and (hopefully) disperse evenly to all 4 ports.
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Because, based on the pic below, it appears (at least to me) that there's no longer any way to adequately attach and seal it to the head. The only way I can see to do it, would be to make a long machined/convoluted rectangular head adapter that would serve as one wall of a 2-pc plenum.

Even then, there are some places around the perimeter that appear to have only 1/4-inch or less of sealing width to contain your targeted 100psi boost pressure! <eek> Also, how will you seal it to the head? I ASSume that you intend to make it from aluminum AND seal it with RTV(?). If so, you're gonna have to deal with two metals having vastly different expansion rates, which will PROBABLY "shear" your RTV seal.

BTW ~ I'm not tryin' to dash your optimism as "Debbie Downer" ~ rather, I'm trying to be realistic.

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So something like this? This is how they do some of the aftercoolers in marine applications of these motors (and the 6BT). This style could be made pretty easily and have it bolt to the flange face I have now. My inlet would be on the other side though so it wouldn't be making the 180deg turn like this one would be.
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As for the intake to head surface, it was sealed with RTV previously and that is how all of these style intakes are sealed to the head. On some of the truck pull applications they see 150-200 psi of boost. Some intakes are aluminum where others are stainless but, most of the runner style intakes, like the one I currently have, are stainless.

My plan was, at minimum, to use some sort of epoxy to build up some of the odd shaped areas to make it so I can try and use an oring to seal the flange to the head instead of RTV.

 

YES ~ Something almost exactly like that. I doubt that you'd need that much height, however, and of course, you don't have any need for water running thru it. Also, I would probably add a few interior "pillars" from one side to the other, to prevent/minimize "ballooning".

BUT.....rather than any "upsides", I only see downsides for milling off what was formerly the existing "shelf", since it provided an infinitely better surface for attaching that plenum ~ BUT.....that's just me.

As said, however, I also would've entertained removing the "top" of that shelf at the front, all the way to the end. One of the so-called "advantages" you claimed for milling off the shelf was porting access ~ BUT......the OEM ports look cavernous ~ DUNNO.

 

Ok I will work on a design similar to that. I'll probably only go high enough for clearance over the injection pump then. Definitely will be adding some support to prevent ballooning. As for the ports, they have already been heavily ported and many of the large casting obstructions that are normally there, have been removed. That's why they look so large (I did not do this part though). I will see what I can put together for a design. I appreciate the input.

I really wish there was a better way to get good distribution instead of the whole killing the air velocity thing. It definitely makes sense but my mind keeps telling me you want to maintain velocity and direct it, not kill it. You can't argue with results and data though

 

Loss of velocity is most certainly one of the results of making the ports so large. That's why I initially suggested using the A+B epoxy to fill 'em to a more uniform size from their opening "mouths" to the area surrounding the SSR (short-side radius) above the valve pockets.

I'm convinced that a trapezoidal plenum similar in shape to the marine unit you posted, would have pretty decent distribution if the floor dumped into the stock full-length opening or trough (would necessitate removing the "roof" at the front, as prev mentioned) above the original "shelf". BUT........that's just THEORY and intuitive speculation w/o any actual testing with a velocity probe.

As for mounting the plenum to the original "shelf", I probably would've made an adapter, retained by flathead Torx bolts, that allows the plenum's mounting flange to be positioned wider and longer than the cast "shelf", thus allowing the plenum ID to match the ID of the (full-length/width) "shelf" opening. BUT.......as said, that's just speculation, based on my limited understanding/knowledge of CFD. GOOD LUCK!

 

I was able to make some progress on this and would like to get a bit of feedback and suggestions if possible. I thought about it a bit more and decided to just modify the current runner style intake manifold I have to make it a side feed, similar to the marine style one I posted above, instead of the front feed. I have the angle portions chopped off but have not made the hole for the inlet tube yet. I might end up cutting more off the angles to have it follow the hood line a little better, but it does fit under the hood now. Volume wise, I have gotten it to about 173% of the displacement, not including the runner portion in the head. This also only includes an approximately 1in long stub coming out of the plenum where the inlet pipe attaches via a v-band. In addition, I am going to use A+B epoxy from goodson’s to reshape the ports to match those of the intake manifold runners instead of the dramatic change they are now.

I did some CFD on the original manifold, so I had a reference to compare my new design to, and unsurprisingly, the rear cylinders were heavily biased. As far as the CFD parameters go, I made the assumptions that the air coming out of the intercooler and into the manifold would be at 100 psig, 150°F, and dry. This gave me an air density of approximately 2.56e-4 lb/in3. I will more than likely be using water injection to aid in the interstage cooling so the air technically won’t be dry but for the purpose of comparison, it will work.

With my engine parameters and power goal of around 600whp I am going to need around 80lb/min of air to achieve this, or approximately 1000 CFM at atmospheric temp and pressure at my location. Using 1000 CFM going in as an easy number, the outlet CFMs from rear to front were 308, 284, 224, 180 so a total spread of 128 CFM (for the initial manifold). The outlet boundary conditions were set at 0 psig. Seeing as this is a mechanical diesel, I don’t have an easy way to control individual cylinder fueling to compensate for uneven air distribution so, I want to get it as even as I can.

I did a couple iterations of this design but have gotten the outlet flows from back to front to 235, 268, 267, 225 (total spread of 43 CFM). Iteration changes with results noted below. It is worth noting that the front two cylinder ports are slightly closer to one another than the rest so that is why rev2 has the inlet in the center of the two middle runners vs the center of the plenum.
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Here are the visual results from the simulations as well.

Initial:
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Rev1
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Rev2 #ad


Rev3
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I do need to run another simulation with the curved inlet coming into my new manifold to better represent how the air is going to be distributed when it enters the plenum as the air is going to be biased a bit towards the back after the turn in the pipe. I am also going to try and put together a complete model including the runners to see if anything changes. I have a couple more things I would like to try to get the distribution even closer as well but wanted to see if you guys had any other suggestions before I cut the hole for the intake pipe and weld it all up.

 

I'm very impressed with the improvements in distribution that you've tentatively made, as evidenced by the CFD simulations!! IMHO, the ones you obtained with the original design were horrific, lol. As you found (and, as others have confirmed), flow is usually biased to the rear runners of a front-entry log-style manifold.

Since you've apparently not chiseled the final design in stone, and ~ just for shits & giggles........is it possible to run a simulation with the air entering into the plenum from the opposite side (charge pipe over v/covs)?

Outta curiosity......is the CFD program you're using available for a reasonable cost (or free)? TIA! Even if it's not perfect, having real data to back up my intuitive thoughts has gotta be better than just talkin' outta my ass, lol.

 

Yea I can swap it around for shits and giggles but it won't fit under the hood then for sure unless I squish the pipe to an oval and would require me to redo a large portion of my intercooler piping. I was also considering seeing how it would do if I made the inlet on the bottom, between the middle two runners, even though I know it wouldn't fit. I am wondering if moving the inlet closer to the floor of the runner inlets will help with distribution since it will force more air up to swirl it around. I think I am also going to try and extend the pipe into the plenum some more to see what it does.

The CFD program I am using is called Simscale. It is cloud based and it is free to a point. You get 10 free simulations (limited options) that will give you numerical data for trials before you have to sign up for the package. After that you can still run the simulations until you are out of "core" hours but they are purely visual as far as outputs go. So far I am pretty impressed with it and I am considering signing up for the actual package.

 

How would an oval entry hole affect it?

ks

 

I tried a reverse cone style transition from round to oval and it didn't seem to make much of a difference in the flow distribution. The flow more or less just stayed in the round shape and didn't spread out much in the transition. Let me see if I can find the results. Granted, I did it with one of the previous manifold styles I was trying but I would think it would be relatively similar.

 

Well the next iteration didn't really turn out well. The standard deviation and total spread are still around the same but now the second cylinder from the back has a decent bit more flow. CFM numbers from back to front are 232, 279, 255, 233. STDEV is 19.1 and spread is 46.5. This is still better than the initial manifold but a little worse than the last iteration. The changes I made were increasing the internal extension from 1.9in to 2.9in, cut a little more off the angles to make it fit the hoodline better (this reduced volume to 168% of displacement), and added the pipe geometry for how it will come into the plenum. I might try shifting the inlet towards the front again (no longer centered on the plenum) to see if I can get the majority of the airmass to be in the center again.

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I did a few more iterations and got to a point where I feel pretty comfortable with the distribution. This revision still has the increased top cuts (for hood clearance) but now the extension into the plenum is 2.4". CFM distribution from back to front is 247.6, 258.7, 258.0, 234.4 with a spread of 24.3 CFM (initial spread was 128 for reference). The standard deviation of the population is 9.9 CFM which is significantly better than the initial 50.2 that I started with. Air velocity in the ports are also significantly closer. Initially the spread for velocity magnitude at each port was 1203 in/s for the max values and 1125 in/s for the average. The last revision has a spread of 333 in/s for the max values and 162 in/s for the average values.

I am very happy with that result so the next task is to weld it all up and then epoxy the runners in the head to match.

Here's the CFD pictures:
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I left all the parameters the same as the last but I swapped the inlet to the other side with just the straight inlet I initially had. The results weren't all that great as it biases the outer cylinders by a good bit. CFM distribution from front to back is 299.3, 204.2, 195.1, 299.3 with a spread of 104.2.

And the pictures:
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Got the manifold all finished up and got the intake pipe changed to fit. Next step is to bend up the injector lines. I can't wait to be able to put my billet valve covers on since the factory ones are pretty ugly haha.

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Also got the head epoxy pretty much complete. I have never used that stuff before but it is pretty awesome, messy, but awesome. Using water on your hands makes it 1000x easier to shape as well. It does make a huge mess though.

Picture of the head with my scanning spray all cleaned off and in the middle of cleaning/grinding for epoxy prep.
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After port matching the runners with epoxy from a template I made from the manifold. I need to do a little bit more to fill in the last few low spots but I am almost there. I also added some epoxy around some of the lower bolt holes to bring them all up to the same face. You can see in the before picture that they don't all have full support around them.
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I am on the fence for what I want to do for a gasket now though so any input would be greatly appreciated. Normally people just use RTV for this which I am not a huge fan of. Ideally I would use o-rings but I don't think there is enough material there on the top and front edges. I need to do some measuring and whatnot still to find out. If I can't make o-rings work, I am wondering if a solid copper gasket would work better than RTV. Another option I have considered is just using Hylomar as the gasket but I haven't been able to find out if it works as a pressure seal. Thoughts?

 

Had to go back to pg. 26 to find this conversation. Can't believe it's been 5 years. Lol. I took your advise to cut back the runners about an inch, which leaves about 2.5 inches from the cover plate, then I was able to make bellmouth entries which was a total pain trying to weld this cast intake. Runners opened up to about a 2.41³ CSA, had to cut the intake in half to reach the entire tract. I'm about to start welding it back together but before I do so I had a question about adding the oval tube to bring the air charge to the bottom plate. If I extend it about 2.5" from the bottom plate the exit will be right next to a couple of the runner inlets. Do you see a problem with this? I'm afraid of overfeeding those closest to it. Take a look at the pics and tell me what you think. Thanks.

 

Awesome project! You've done some really cool work.

Also, you can get small o-rings. 1/16" diameter cord stock for example and then just glue together whatever length you need. I assume at that size cross section you could seal the head even in the thin spots.

If cutting the o-ring groove would be too difficult I would try the copper piece. I bet having it laser cut wouldn't be that expensive. I would try to maintain a uniform width to maximize crush on it. Since it's all in CAD you could pretty quickly estimate compression forces/pressures from the bolt loads and optimize gasket area accordingly.

Annealed copper has a yield strength of about 11ksi according to google so I would target that.

You might start your own build thread. I know I would be interested to follow the whole project along.

Now I'm rambling but I updated a random shape 2"x20" with a bunch of holes into www.sendcutsend.com and a .040" copper piece is $60 for one. Seams reasonable to me. I'm not sponsored, just a happy customer.

 

Thanks! I really should do a build thread at some point but there is so much to cover that it would take me forever to put together a post haha.

I would love to do o-rings but there really isn't a lot of area in some of the smaller cross sections. I found some metric sizes that might work though but that would require me to machine grooves in the manifold. Even with a small 1.5mm CS o-ring (so I don't have to make my own size with cord), some of the places on the head would only have around 0.040" of area after the outer edge of the groove and I don't know how I feel about that. I only have access to manual mills currently so cutting a nice o-ring groove is going to be a bit difficult unless I outsource it, which I would rather not do.

If I go the solid copper route I would definitely be using SendCutSend as I love that place. I have used them for a ton of stuff on various projects.

I am still working on bending new injector lines so I have time to mess with different ideas and whatnot. Been rather busy with other stuff in life too so that slows progress a bit as well.

 

The distribution problems you are seeing are mostly associated with the velocity of the air entering the plenum. Where possible, the pipe should be taper up to the maximum possible CSA as it approaches the plenum.

 

We will be doing a small production run of these in CNC'd Billet + sheet metal fabricated if anyone with a coyote is looking for a good boosted manifold.
It'll look far better, but we do not yet have a final rendering.

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