Help me design a carbon fiber intake manifold.
 

Background: I'm taking a manufacturing/design program at school and am in my final year. Part of this year is a design/manufacturing project that encompasses the principles taught in the course. This can be anything from CNC machining, welding, tool design, composites, plant layout.... Very wide open.

My project is a carbon fiber intake manifold for the SVX. I may accompany this with a new cold air intake (also CF, of course). I've been doing some research, but by no means am I an expert in engine design, so I'm looking for advice and help with this project. I've got the basic dimensions down and am currently working on my design in CATIA.

In case anyone's wondering why carbon fiber? Lightweight for one, the OEM manifold is quite hefty. I should be able to trim it down to just a handful of pounds. Heat transfer is the second big thing though. I'll have to see what happens once it's installed, but I'm hoping that the CF will keep intake temperatures lower. It may heat soak faster due to the low mass, but once air is moving through it it should cool rapidly.

My questions at the moment:

1. It's too complex to incorporate the IRIS system into what I'm making given my time and ability constraints and this leaves me with the choice of a dual or single plenum system. Should I have the throttle body feeding a pair of smaller plenums, one for each cylinder bank, or should I have a single, larger plenum? The way I see it the dual plenums will have walls facing the runner inlets, given better reflection for resonance, but can the ECU read and compensate for the two banks possibly having slightly different airflow and fuel requirements?

2. Plenum volume? Most of the articles I've found relate to forced induction manifolds and suggest plenum volume be 1.5-2 times the engine displacement, but not many have anything to suggest volume for N/A engines. 0.75 times displacement?

3. Runner length? I'll be keeping the diameter to ~45mm I.D. and will be using raised velocity stacks/trumpets inside the plenum. I'd like to target ~6000 RPM for peak power to combat the EG33's tendency to fall off in the upper rev range. From what I've found so far I should be aiming for ~10" runners above the injector stacks.

Any other thoughts or comments are welcomed, this is going to be a challenging project but also a lot of fun.

Some of the references I've been reading:

http://www.amsperformance.com/pdfs/intakemani.pdf
http://www.velocity-of-sound.com/vel...alculator2.htm
http://horsepowercalculators.net/int...anifold-design

Re: Help me design a carbon fiber intake manifold.
 

This article may or may not be relevant to your interests... and not its not purely honda related

http://www.team-integra.net/sections...?ArticleID=466

Re: Help me design a carbon fiber intake manifold.
 

I think I've come across that article before, it's a good description of the resonance tuning principal, which is what runner length is all about. The concepts are universal to all manifolds, so it's definitely going to be part of mine.

Re: Help me design a carbon fiber intake manifold.
 

Cool project. I'm just trying to imagine how it would look under the hood though. It's going to be a challenge to fit 10" runners with two separate plenums (pleni? lol) in the engine bay.

Re: Help me design a carbon fiber intake manifold.
 

Here's a very rough idea of how it's going to look. This was done before I pulled the intake off my car and took proper measurements, so a lot if going to change.

http://www.subaru-svx.net/photopost/...ium/Render.jpg

I'm going to have the flanges anodized gold to match the BBS wheels, along with the throttle body. Bling bling :cool:

Re: Help me design a carbon fiber intake manifold.
 

Looks good as long as it's low enough for the hood to close, lol. Are you going to be using the stock TB? How are you going do do the vacuum lines and whatnot?

Re: Help me design a carbon fiber intake manifold.
 

Stock TB, keeping the PCV system but getting rid of EGR. I may use a Vibrant vacuum manifold to take care of my vacuum line needs:

http://vibrantperformance.com/catalo.../2690_WEBL.jpg

Re: Help me design a carbon fiber intake manifold.
 

Cool. Care to explain how that thing works?

Re: Help me design a carbon fiber intake manifold.
 

This is just a guess but see that larger opening facing us, that is where you put main vacuum then you just attach nipples to any or all of the other places and route lines to them.

Re: Help me design a carbon fiber intake manifold.
 

If you google eg33 + airplane you will find dozens of custom intakes if your plans aren't set in stone.

Re: Help me design a carbon fiber intake manifold.
 

Figured I'd give you guys an update. Design work is progressing well, I've got what should be close to my final product:

http://www.subaru-svx.net/photopost/...medium/Iso.jpg

http://www.subaru-svx.net/photopost/...medium/Top.jpg

http://www.subaru-svx.net/photopost/.../Left_Side.jpg

This design has runner lengths averaging 6.8". The injector stacks are another 3", plus a few more inside the head ports to the intake valves. Total runner length is therefore around 13-14 inches, which should be near optimal for some high RPM power.

Within the next little while I'll start cutting test parts out of arborite on the CNC mill to check my bolt patterns and then ordering up the aluminum to cut my flanges. I've decided to use braided carbon sleeving for the runners, which should give me the best contouring. When I made my CF swaybar (see the link in my mod list) we wrapped sheets of carbon over the stock bar, and making the fabric contour to the bends in the bar was very difficult. The sleeve should make life much easier.

http://img.alibaba.com/img/imagerepo...web16_4316.jpg

My biggest delay at the moment is deciding how to make the composite parts. I have a number of options, but I'm trying to get to the most realistic for my requirements. I'm also trying to nail down a resin choice. The one my school stocks would turn to goop at the engine's operating temperature, so I need something with good high temp performance.

In case anyone's curious about me selling this as a bolt-on mod in the future... It may be doable, depending on my techniques, but this would not be in any way cheap. If you look at other CF intake manifolds they range from $1200-$5000. Between the time and material cost I doubt I'd hand one over for less than $1000.

Re: Help me design a carbon fiber intake manifold.
 

I don't guess you could make it out of something else. Looks very cool though. I hope you get one made and see the improvement it makes :)

Re: Help me design a carbon fiber intake manifold.
 

To make that in one piece is going to be a big challenge, and this is from someone in the composites business :O

One idea is to make each runner separate, the plenum separate, and then bond them together. You will need some fixtures to do this correctly

Another is to CNC cut the shape out of high density foam, and then laminate over the top of the foam and use acetone to dissolve the foam afterwards.

Lots of work ahead, should be worth an A+ if you can pull it off though.

Re: Help me design a carbon fiber intake manifold.
 

lol! Definitely no intention of making it in one piece. Each runner will be made individually and the plenum will be done in a top and bottom half. I already have a tooling board made to hold the injector stacks in the proper location. I'll bolt the new flanges to the stacks, locate the lower half of the plenum, drop in the runners, and lock down the top half of the plenum.

My current idea for making the runners is to make a two piece mold that is the correct inner diameter. I'll use a ceramic pottery mix to coat the inside, remove and bake that, and then wrap that with the CF sleeve. The reason there is that the high temp epoxies I'm looking for all require an elevated temp cure schedule, and suggest they remain on the mold tool to prevent warpage. After curing I can break out the ceramic and voila, intake runners.

Re: Help me design a carbon fiber intake manifold.
 

If you have two halves for your runner molds, you could skip the ceramic and use an inflatable mandrel instead and make your molds to the OD. Sort of like a backwards form of vacuum bagging.

But hey..this is your homework assignment, not mine :lol::lol: