Making a carbon fiber airbox - input appreciated
 

Hi all,

As I test fit the engine in the latest Gretchen I began measuring and planning for the air filter assembly. This car has an aluminum Carrera intake, and from a rough placement in the engine compartment I have about 6" clearance from the throttlebody to the firewall.

I had used a giant oval-cone K&N filter with one of their 90 degree elbows on this motor in another car in the past and it would fit this car too but 1. it looks ghetto (my diagonal cut to fit the throttle body wasnt clean, 2. it is a heavy mother and 3. it indiscriminately takes air in from throughout the engine bay.


So in the spirit of competely skunkworking this thing, I came up with a plan...my priorities were to address those 3 things above. I have done enough fiberglass work to know I dont have the skills to turn out a piece that would be acceptable to me. So I concocted an approach to use some pre-fabbed carbonfiber pieces and plates to make something.

I drew up plans for and order some pieces. Sorry, I am travelling now and dont have the drawings with me but it is basically a 90 degree 3.5" elbow from the throttlebody to an airbox located over the 4-5-6 cylinder bank mounted on the stock intake bolts. The elbow enters the airbox on the driver's side. The box will measure 5.5" tall x 12" wide by 12" deep. The box has 5 closed sides and its open end facing the rear of the car. A rectangular filter will fit into the open end supported by a 1" CF flange around the perimeter made from the 90* CF angle. Then a lid also with a CF angle flange sandwiches the filter in place, and forms a mouth aimed at a 45* angle right into the decklid grill. I know, a picture is much more helpful...

Here is my list of materials:

90* elbow from carrera throttlebody to airbox:

CF Elbow

http://www.intakehoses.com/mm5/graph...CF90-350X6.jpg

CF plate forming the box and filter mouth:

solid CF prepreg plate 1/16"







CF 90* angle reinforcement for corners and filter flanges:

CF angles for corners and flanges

https://dragonplate.com/images/photo...-angle-sml.jpg


Filter:
Rectangular K&N filter

https://static.summitracing.com/glob....jpg?rep=False

I havent worked with CF before. I found this video helpful in building confidence...lets see if that is misguided...

https://www.youtube.com/watch?v=EWzN6GZeEzs&t=35s

Easy Composites Video

<iframe width="560" height="315" src="https://www.youtube.com/embed/EWzN6GZeEzs" frameborder="0" allowfullscreen></iframe>

I have a bunch of Hysol products on hand for the actual bonding. Initial research incdicated the e120 was the go?


I am interested in input from others about the approach, methods, tips and tricks...

Hi John - sounds like an awesome project. If you end up documenting it in detail, check out this link as you may be interested in becoming one of our DIY Project Experts.

I've also found the below link to give you some ideas/troubleshoot the install that you're going to be doing. Hope it helps and best of luck!

C2/C4 Airbox Modification / Upgrade


-Dmitry

I would like to have a MFI style airbox set up for my Jenvey ITB's. The Jenveys have straight manifolds, and the spacing between each TB is bigger than the MFI/Weber/PMO type set ups. I was thinking of buying an original MFI airbox, cut and space it out to make it fit, and then make molds out of FG. And then make new ones in CF or FG... Have anyone tried this?

Hi Dmitry,
Thanks, I did that to a 993 I owned years ago.

This was a project of mine. i started off building boats at an early age.
http://forums.pelicanparts.com/uploa...1479782926.jpg

That is so cool. You have skills I will never have. Great job!

Agreed - absolutely love it!

+1 looks absolutely incredible.


-Dmitry

What size is that filter? K&N site calculates needing 65 sq in in filter area, yours looks smaller than that? The one I selected above is also slightly smaller, I may return for a Miata filter which is 6.5x12. Same sq in as used in a new AMG C63 so I cant imagine it would choke a 250hp 3.0.

Kudos for the CF effect/build. However, inlet air temps are pretty much ambient in the engine compartment at speed. Use a paper filter. It's cheaper..... and better.

Sherwood

K&N makes more promises than president campaign speech

Yeah, but I see you used one too! What size is it?

The filter will be partially visible with the trunk open, at least the K&N looks OK and does a decent enough job filtering. The paper ones look like crap as they yellow/grey almost immediately.

robust filter sized to fit my project
http://forums.pelicanparts.com/uploa...1480010905.jpg
http://forums.pelicanparts.com/uploa...1480010925.jpg

After seeing what passes through a K&N filter I would NEVER use one on my car... Stock paper element works just fine.

Lo0ks like you have lots of other work on car. why not something like this

AireTEK Fresh Air Induction Kit-HighFlow, 911, 1984-89

Porsche 911 (1974-1989) - Intake System - Page 2

Welcome to Rothsport Racing - Engine Products
K&N

The first one doesnt look like it will clear the firewall with an alu intake and stock throttlebody. Second not sure either will fit the 90mm tb? Both still leave a bit of a .... how do I say this...not the aesthetic I am hoping for.

Thats for the later 964 intake I believe. The twin-chamber like yours. Mine is the simple 86-88 single-chamber alu intake.

I've been using them for 30 years on every machine I own (bikes, cars, diesel truck, race and public roads) and have never had a problem with dirt getting past them.

Would you mind sharing how you made the manifold?

Did you make a female mold or a core to lay up the carbon?

How did you manage the seams, lap joints?

Thanks,

Looking forward to your feedback.

I have build many variations of the resonance flap airbox. this version was resin infused with a male part. see in the picture the advancing line of resin as it gets drawn across the part under vacuum. very cool to watch.http://forums.pelicanparts.com/uploa...1480176851.jpg

How did you manage the seams, lap joints?

started out taping the seams then with the infusion in an attempt to cut down the cost went to just bonding with flangeshttp://forums.pelicanparts.com/uploa...1480177662.jpg
http://forums.pelicanparts.com/uploa...1480177689.jpg

Yes, they are made for (originally) racing and racing lumps are rebuilt often.
I know what passes thru K&N even if washed/oiled per sched...in the Az dry countryside so much dust/dirt came thru a K&N it would clog the idle jets on my carbs to the point it would not run and simply stall out.....you could scoop the grime out on your fingers.
Replaced with a paper element and have never had that issue and the carbs are clean.
K&N sucks in fine particles and if you are good with that ok.

Wish list...carbon fiber CIS airbox.

Thanks for the feedback, very detailed! It looks like your also bonding aluminum flanges to the manifold for the rubber couplers. Did ever consider building these features into the the manifold itself (there appears to be sufficient draft) or does the geometry make it not possible i.e stepping up to the larger OD and maintaining the ID?

I have a friend of a friend making skiffs using the resin infusion technique. He has much better control of the fibre to resin ratio, reducing mass and cost, increasing the strength of the boat. It did take some time to identify the resin feeds and vac locations.

Thanks for sharing.

When I started to make the 997 GT3 airbox I did incorporate building the coupler nipple into the ends of the halveshttp://forums.pelicanparts.com/uploa...1480210263.jpg

center sectionhttp://forums.pelicanparts.com/uploa...1480210617.jpg

Not to break up the vacuum-layup pornfest, but I have a few open questions on constructing a simple box from CF panels, elbow and flanges.

The pics above have certainly motivated me to make mine look as nice as possible, thats for sure. I wont be matching that level of proficiency though.

A few questions;
- would love to see some somple boxes, for intake or other purposes
- I am planning to cut the straight edges with either a table tilesaw with a smooth diamond blade, or my tablesaw with 100 teeth.
- Then straightening/finishing the edges with fine paper on a straight sanding block
- Using L-section cf angle to reinforce the corners. I would put the angle on the outside if I cant get the edges perfect, otherwise the angles bonded on the inside of the corners?
- Hysol 120e as a recommended bonding agent?
- Rough up the gloss panels at the bonding surfaces?
- Anyone use dzuz fasteners with CF? I need a way to "sandwich" the filter between the main box body and the intake piece. What have people done? I usually use rivets to fasten the dzus springs but I dont think CF likes being riveted.

Love the pics and help. And yes, I am listening. I may toss the K&N...

I have some spare fancy-dancy titanium 5mm bolts, any recommendations for 5mm captive nuts or threaded plates made to be bonded to CF or fiberglass panels at each corner instead of dzus fasteners? A quick flick through aircraft spruce didnt have what I think I am looking for?

I imagine the section through coupler nipple inner diameter isnt constant, it follows the outside profile?

BTW how did you lay up the centre section, is there a foam core to fill out the heavier sections?

@JohnJL - why do you plan on using plat CF panels, the advantage of using composites over sheet metal is that you are able to create a unique form.
I have used dzus fasteners with carbon fibre and it rivit's fine as long as you us a large head or backing plate to distribute the force.
However if you shall add an insert you'll need to use something which will not crush the CF, in boat building ply is often used at hard points.

Perhaps dsfnctn can provide us with some images of threaded inserts and attachment points.

This is a cheat sheet that I made to show a product line that I use in some of my builds. http://clickbond.com/
They are very well thought out. I like the nutserts with the rubber holding devices. They are cool because the nut is captive in the plate with a clip that allows it to float and also replace if buggered.You just dril the hole and the rubber tube holds it in place until the glue drys ,then you yank the rubber. also the ones pictured with the holdig devices have double backed tape to hold in place and more important when they are designed for the exact amount of squeeze out glue. I have used rivits , rivnuts etc what ever it takes I find my guys bugger riv nuts when they hurry and don't have the hole exact they strip real easy.

The rubber coupler ends on the 997 part are made by whipping the ends with uni directional carbon and then when it starts to cure put the rubber coupler on and it makes the imprint . You get that?
foam core radius between tubes


http://forums.pelicanparts.com/uploa...1480291925.jpg

Those click bond fasteners are very cool, certainly simplify fastener installation. Thanks I forwarding them to my bud.

Regarding the coupler ends, assuming your using a male mold as shown before, you are locally building up the end of the tube with uni and then pushing the rubber coupler on to make the imprint. You may also be doing this once the two halves of the mold are bonded together and then completing this process.

Would you mind sharing images of the 997 intake molds?