Help me design a carbon fiber intake manifold.

[Crazy_pilot]

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/velocity_of_sound/calculator2.htm
http://horsepowercalculators.net/intake-manifold-design/intake-manifold-design

[StatGSR]

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

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

[Crazy_pilot]

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.

[icingdeath88]

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.

[Crazy_pilot]

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/data/500/medium/Render.jpg

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

[icingdeath88]

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?

[Crazy_pilot]

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/catalog/images/2690_WEBL.jpg

[icingdeath88]

Cool. Care to explain how that thing works?

[92 SVX]

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/catalog/images/2690_WEBL.jpg

Cool. Care to explain how that thing works?

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.

[michael]

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

[Crazy_pilot]

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/data/626/medium/Iso.jpg

http://www.subaru-svx.net/photopost/data/626/medium/Top.jpg

http://www.subaru-svx.net/photopost/data/626/medium/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/imagerepos/cn/20/cn209765981/1269235296664_hz_myalibaba_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.

[STeeL25T]

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 :)

[Stevebsy]

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.

[Crazy_pilot]

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

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.

[Stevebsy]

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:

[Crazy_pilot]

I've thought about that too, using an inflation bladder, but the problem again comes when I need to bake the layup. Every part of the mold and bladder would need to be able to stand up to 350 degrees or more, and making the mold out of a heat resistant material instead of whatever I happen to have at hand would up the cost significantly.

[Stevebsy]

I've thought about that too, using an inflation bladder, but the problem again comes when I need to bake the layup. Every part of the mold and bladder would need to be able to stand up to 350 degrees or more, and making the mold out of a heat resistant material instead of whatever I happen to have at hand would up the cost significantly.

What Resin are you thinking of using? There are bagging/bladder materials that will take the high temp so that shouldn't be much trouble.

Just curious, have you (or anyone else) measured the actual temp of the intake under operating conditions? That could help you pick the right resin system.

[Crazy_pilot]

I've been exchanging e-mails with Aircraft Spruce, who have suggested De-Comp's HT212 system (link (http://www.decomp.com/resins/laminate/212_38699.htm)). It has a 290*F distortion temperature and some flexibility (better vibration resistance vs uber-rigid/brittle stuff).

I probed my engine with an IR thermometer before I parked the car for the winter and the highest temp I could find, short of aiming it at the exhaust, was 92*C (198*F), so I think 225*F is a good starting point for my epoxy search.

[svxfiles]

Just curious, have you (or anyone else) measured the actual temp of the intake under operating conditions? That could help you pick the right resin system.

Normally the intake manifold does not go over 200°f, even in the summer on a 100°f day.:)












MMMmmmmmmmmmm, 100°f day!:cool:

[Johnybeas]

Interesting project. Can't wait to see the results.

[Crazy_pilot]

Bit of an update. I spent a bunch of time in the machine shop today turning billets of aluminum into piles of chips, and MDF into sawdust. The results, 2 MDF molds to make the plenums, 2 flanges that will bolt to the injector stacks (one attached in the pictures), and a flange that will allow the throttle body to bolt on:

http://www.subaru-svx.net/photopost/data/500/medium/IMG_0189.JPG

http://www.subaru-svx.net/photopost/data/500/medium/IMG_0193.JPG

http://www.subaru-svx.net/photopost/data/500/medium/IMG_0194_1_.JPG

And the big beast that helped this all happen:

http://www.subaru-svx.net/photopost/data/500/medium/IMG_0192.JPG

I have 3 yards of twill weave carbon sitting beside me and a gallon of PTM&W 2520 epoxy, which has a service temperature rating of over 300*F. In the mail currently is 5 yards of 2" braided carbon sleeve to make the runners. (No pictures of the jig to make those, but it's ready)

This weekend will involve sealing and prepping the molds. Lay-up to commence next week.

[Cam]

Very nice work on the aluminum pieces. Mold looks promising as well. Very nice progress. :cool:

I recommend anodizing for the aluminum parts. One of the things that happens between aluminum and carbon fiber is, since they are dissimilar materials, they will corrode. More specifically the aluminum will corrode. You will effectively stop this if you anodize the part and/or paint the mating surfaces between the stacks and the plenum. Otherwise your beautiful machine work will be for nothing.

Aluminum and Steel, Aluminum and Titanium, CFRP (carbon fiber reinforced plastic) and any of the above can all cause corrosion simply from small amounts of moisture between the parts.

[svxfiles]

HMmmmmm, can you whip up a carbon fibre 4.0 H-6 block?


I'd trade you my soul for it.:o

[Hocrest]

HMmmmmm, can you whip up a carbon fibre 4.0 H-6 block?


I'd trade you my soul for it.:o
Wow!!!! Talk about a lopsided deal :rolleyes: :lol:

[Crazy_pilot]

I recommend anodizing for the aluminum parts. One of the things that happens between aluminum and carbon fiber is, since they are dissimilar materials, they will corrode.

That's the idea. The flanges are all going to be anodized gold to match my BBS wheels.

HMmmmmm, can you whip up a carbon fibre 4.0 H-6 block?


I'd trade you my soul for it.:o

:lol::lol: I'll get right on that.

[Johnybeas]

HMmmmmm, can you whip up a carbon fibre 4.0 H-6 block?


I'd trade you my soul for it.:o

+1.... papapalease??? hahahahah

[svxfiles]

Wow!!!! Talk about a lopsided deal :rolleyes: :lol:

Like anyone HERE would believe that I actually HAD a soul!:lol:

[svxfiles]

:lol::lol: I'll get right on that.

REALLY?!:eek:

OK, Great, got my soul right here,,,its never been used,,,
I'll keep it in a box for ya,,,









TEEHEEHEEHEE, snort!

[httrdd]

That soul comment reminded me of spongebob when mr krabs has a line of people with IOUs waiting for his soul. Is it the same for you too? Anyways carry on!

[Stevebsy]

Very nice work on the aluminum pieces. Mold looks promising as well. Very nice progress. :cool:

I recommend anodizing for the aluminum parts. One of the things that happens between aluminum and carbon fiber is, since they are dissimilar materials, they will corrode. More specifically the aluminum will corrode. You will effectively stop this if you anodize the part and/or paint the mating surfaces between the stacks and the plenum. Otherwise your beautiful machine work will be for nothing.

Aluminum and Steel, Aluminum and Titanium, CFRP (carbon fiber reinforced plastic) and any of the above can all cause corrosion simply from small amounts of moisture between the parts.

Ditto on the anodizing, very necessary to have some sort of coating inbetween the CF and the Aluminum.

Seal those molds really really well. MDF will suck in whatever sealant you apply. Shellac works pretty well. If you do not seal it really well, then you will be chipping the mold off of your part :( I have learned this the hard way a couple of times unfortunately... Also..I hope you put some draft angle into those molds :)

What will you use for your mold release?

I'll be interested to see how you are doing the runners.

Looks good so far!

[Cam]

I would go as far as to find an industrial strength primer that you can paint the tops of the stacks with. It doesnt need to be noticable, but all the mating area plus about .050". Hardly anyone would see it, and you would be sure not to have corrosion (at least for a long time :rolleyes:).

Can't wait to see this get completed.

EDIT : Also, what are you doing for gaskets between the manifold and the stacks?

[Crazy_pilot]

Ditto on the anodizing, very necessary to have some sort of coating inbetween the CF and the Aluminum.

Seal those molds really really well. MDF will suck in whatever sealant you apply. Shellac works pretty well. If you do not seal it really well, then you will be chipping the mold off of your part :( I have learned this the hard way a couple of times unfortunately... Also..I hope you put some draft angle into those molds :)

What will you use for your mold release?

I'll be interested to see how you are doing the runners.

Looks good so far!

Don't worry, we've been pounding out MDF molds all month. One of the other guys is making a CF cargo roof box, another is making a CF suitcase, all from MDF molds.

The runners are going to be tricky as ****, but I think I've got a process nailed down reasonably well. I'll do a full update on that aspect in a bit.


I would go as far as to find an industrial strength primer that you can paint the tops of the stacks with. It doesnt need to be noticable, but all the mating area plus about .050". Hardly anyone would see it, and you would be sure not to have corrosion (at least for a long time :rolleyes:).

Can't wait to see this get completed.

EDIT : Also, what are you doing for gaskets between the manifold and the stacks?


Gaskets are just going to be the OEM ones. I haven't goofed with the dimensions of things or ported the runners out to the point that I would need different gaskets.

[Cam]

Even between the cf and aluminum?

[Johnybeas]

bump any more pictures??

[Crazy_pilot]

lol, nothing super new at the moment. Molds are now sanded, sealed, painted, cleared, wet sanded, polished and waxed. I have all my CF and epoxy ready to go and am planning on laying up the plenum halves tomorrow night (if I have time... Going to some musical thing for the girlfriend). I'll take some shots of the molds, layup, and runner jig tomorrow.

[Crazy_pilot]

Update!

Molds painted and prepped:

http://a7.sphotos.ak.fbcdn.net/hphotos-ak-snc6/190751_10150471023820721_514340720_17767414_200509 8_n.jpg

One plenum half laid up and bagged:

http://a5.sphotos.ak.fbcdn.net/hphotos-ak-snc6/196957_10150471024010721_514340720_17767417_210428 0_n.jpg

Got it out!

http://a6.sphotos.ak.fbcdn.net/hphotos-ak-snc6/200193_10150471024195721_514340720_17767418_299255 9_n.jpg

Got the second one too! (this one brought a bit of its mold with it)

http://a7.sphotos.ak.fbcdn.net/hphotos-ak-ash4/188954_10150471024735721_514340720_17767423_872778 _n.jpg

And the runner layup tool. The vertical plate has six different holes on the back the correspond to the individual runners. Bolt the upper mandrel in place, fill the gap with foam, and voila, runners.

http://a5.sphotos.ak.fbcdn.net/hphotos-ak-ash4/188630_10150471024345721_514340720_17767420_292417 3_n.jpg

[Blacky]

Nice work, looking good!:cool:

[icingdeath88]

So are you sure you can't make another one??

[Crazy_pilot]

There's nothing stopping me from making a second one, other than time and money, and access to a CNC mill. I doubt it'll happen though, I only need one and it would cost quite a bit for someone to commission me on a second.

[Crazy_pilot]

Small update: No new parts made since I've been working on the report that accompanies this project (currently 32 pages long... my fingers hurt), but I have an estimated final weight for the manifold.

*drum roll*......

5 pounds.

And that's a conservative estimate, I weighed the parts I have which are untrimmed, and the flanges I've already machined, and extrapolated a bit. I wouldn't be surprised if the weight actually turns out to be closer to 4 pounds.

[icingdeath88]

What's the stock manifold weigh?

[Cam]

What's the stock manifold weigh?

If I had to guess I would say 15 pounds. Total shot in the dark, though.

[Jay Wrix]

very pretty. I want!

super great work, sell a couple! I really wanna get into CF work.