Building a custom airbox?

I've been looking at building an airbox for the DCOE throttle bodies on my car, but I'm not exactly sure how to go about doing it.

I'm not a fan of leaving the throttle bodies to suck hot air from the engine bay and I need to come up with a filter solution for them.

The production solutions look very nice, but most are $300+ and that is out of my price range right now (unless someone wants some 17x8" BMW wheels)

I was thinking of using some foam blocks to build a mold and then fiberglassing it over with supplies from the local Home Depot Racing Supply Company.

Would this resin stand up to under hood heat well?

What about applying pressure to it in some form of pressurized air?

Another option would be to use aluminum, but welding it is the issue for me.

Use the blue foam insulation from lowes/home depot. Carve it to the shape that you want, including holes for airhorns and intake snorkus. Cover it with a wet-layup of CF--or fiberglass--at least two layers and let cure. Pour lacquer thinner onto the foam to make it dissolve completely--leaving you with a hollow airbox....

Polyester won't be quite as heat resistant as epoxy, but unless it's super close to the header, it shouldn't be an issue. You can always use a heat barrier tape to keep the heat out.

as for pressurizing it---I would think that you could probably make that work, although I'd use an extra layer or two to make sure it was strong enough to handle the pressure.

Per Schroeder wrote: Polyester won't be quite as heat resistant as epoxy, but unless it's super close to the header, it shouldn't be an issue. You can always use a heat barrier tape to keep the heat out.

IIRC 924s have crossflow heads so heat from the header shouldn't be an issue.

Overbuild it. I have seen a few Formula manifolds get destroyed by the pressure. I would personally use CF with Epoxy.

I read an article on a product called HyperFiber in Hot Rod a while back. Fiber-glass with and without wire-reinforcement that has the resins pre-loaded in the matrix. Cut the sheet to size, form it with your method of choice (wire holds the shape) and place the finished part in the sun to cure. Clean and neat.

If you layer some wire mesh (like aluminum window screen) between the fiberglass layers it will add a lot of strength but not much weight. Go in layers: form > fiberglass > mesh > fiberglass > mesh > fiberglass.

I feel like an idiot, but I pulled up the home depot and lowes websites and I'm not sure which kind of foam insulation is actually being recommended.

Number 1: http://www.lowes.com/pd_42864-236-263065_0__?productId=3057515&Ntt=foam+insulation&pl=1&currentURL=%2Fpl__0__s%3FNtt%3Dfoam%2Binsulation%26page%3D1&facetInfo=

or option b: http://www.lowes.com/ProductDisplay?partNumber=15348-46086-201549&langId=-1&storeId=10151&productId=3014183&catalogId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

I'm guessing the latter... but I'd rather just ask and be sure.

wawazat wrote: I read an article on a product called HyperFiber in Hot Rod a while back. Fiber-glass with and without wire-reinforcement that has the resins pre-loaded in the matrix. Cut the sheet to size, form it with your method of choice (wire holds the shape) and place the finished part in the sun to cure. Clean and neat.

THIS.

This stuff is awesome.

I'm using flower foam, used to make flower arrangements. Nice and high density, cheap and you can pick it up when you're out with the S.O.

The mesh idea is interesting and it leads me to another thought about alternative screen material.

I had to replace the aluminum screen material in our screen door due to the cat destroying it. I replaced it with a kevlar/fiberglass screen material that I picked up from Home Depot. I wonder if that might work to strengthen the airbox?

Thanks for the ideas, I'll have to get out to the garage and get to it! I'll see what I come up with and post some pictures.

maybe idears here:

http://www.twminduction.com/airbox.htm

The fiberglass/kevlar screen doesn't have enough rigidity, even when folded or curved. If you put a curve in the aluminum stuff, it picks up a LOT of rigidity.

For that matter, why not make it out of .100 thick aluminum sheet? That's easily bent and riveted, use epoxy to seal the corners etc.

I believe you (I've got zilch for experience), but I'm puzzled by the aluminum screen adding a lot of rigidity to a CF part. I'd have assumed that the main way it did that was by increasing the part thickness and thus more effectively putting the CF or 'glass into tension when force is applied.

I was thinking that for a complex part, it might make sense to lay up one or two layers, then coat the whole part with a slurry of resin mixed with microballoons to provide a lightweight sandwich core, and then do one or two more layers on top.

Whether it's feasible to coat a part evenly enough to not wind up with a big blob I'm not sure...

CF? Great stuff and i agree it doesn't need any help, but the OP was talking fiberglass. Three layers of fiberglass cloth will only be around 1/8" thick, it will need some help to withstand, say, 10 PSI of boost.

Got it, thanks!

Wasn't sure what to expect of either, and my all-reading-no-doing background here was fixated on thickness==rigidity...

I was thinking about the fiberglass/kevlar mesh because it would more closely integrate with the rest of the composite and provide strength through its properties and the bonding it has made through the composite.

I would fear the aluminum wouldn't bond properly and could lead to cracking as the part flexes from pressure fluctuations.

Luckily, it is relatively cheap to make, so maybe I'll try both and see what holds up.

I'd love to do a full vacuum layup, but that would have to wait until I have funds to buy the supplies.

I hope you'll post your experiences with whatever you try. I'm still not sure what the induction's going to be on the M42-into-2002 project, but I'm pretty sure anything I learn from your experience will be applicable

I like the flower foam thing. While you are the store getting it.. before sure to get a "hot knife" to help cut it. Basically a heated wire that melts the foam as it "cuts"

edit

Something else to consider. Rather than lots of heavy layers and using mesh for strength. How about adding some internal ribbing. You can use balsa for that and add it after the fact as long as you bond it in properly.. or if you are really good.. form it first and insert it into the foam so that when you lay in the first layers.. it bonds right to it

Here's some interesting info:

http://77e21.info/mstunedintake.htm

I like the balsa rib idea.

I'll definitely share what I come up with. I suspect there will be lots of experimentation to do :)

You can get aluminum to bond to composites but in my experience the best way to do that is with a special bonding agent and I don't remember what it is called. You have to heat it in a vacuum bag when you use it as well. We used it when we where playing with aluminum honeycomb bonded with CF.

mad_machine wrote: I like the flower foam thing. While you are the store getting it.. before sure to get a "hot knife" to help cut it. Basically a heated wire that melts the foam as it "cuts" *edit* Something else to consider. Rather than lots of heavy layers and using mesh for strength. How about adding some internal ribbing. You can use balsa for that and add it after the fact as long as you bond it in properly.. or if you are really good.. form it first and insert it into the foam so that when you lay in the first layers.. it bonds right to it

I would stay away from the flower foam. It's an open-celled foam which means it will more than likely absorb a ton more resin than required. Thus increasing weight and a lot of cursing to clean away.

mad_machine wrote: I like the flower foam thing. While you are the store getting it.. before sure to get a "hot knife" to help cut it. Basically a heated wire that melts the foam as it "cuts" *edit* Something else to consider. Rather than lots of heavy layers and using mesh for strength. How about adding some internal ribbing. You can use balsa for that and add it after the fact as long as you bond it in properly.. or if you are really good.. form it first and insert it into the foam so that when you lay in the first layers.. it bonds right to it

used to make of glass subwoofer boxes.a dn speaker pods. and believe me a couple of layers is plenty to hold pressure. first flower foam is great. you can cut or mash it with your fingers

You can use rope for internal ribbing. make grooves int foam and lay the rope in before you wrap the foam. with cloth.

scooterfrog wrote:

mad_machine wrote: I like the flower foam thing. While you are the store getting it.. before sure to get a "hot knife" to help cut it. Basically a heated wire that melts the foam as it "cuts" *edit* Something else to consider. Rather than lots of heavy layers and using mesh for strength. How about adding some internal ribbing. You can use balsa for that and add it after the fact as long as you bond it in properly.. or if you are really good.. form it first and insert it into the foam so that when you lay in the first layers.. it bonds right to it

used to make of glass subwoofer boxes.a dn speaker pods. and believe me a couple of layers is plenty to hold pressure. first flower foam is great. you can cut or mash it with your fingers You can use rope for internal ribbing. make grooves int foam and lay the rope in before you wrap the foam. with cloth.

Maybe for a sub box but remember this is a race car. Strength to weight will matter somewhat.

In reply to Merc:

I think the foam is just acting as a mold and will get removed at the end.

There are appear to be two different types of flower foam. The white stuff is more open and could be problematic for a nice finish and the green/brown is more closed and should provide a nice finish.

Either way, from the reading I've done on Instructables.com and other sites, if you wrap it in clear packing tape, you can improve the surface finish and make it easier to remove the foam as it all dissolves from the solvent.