Making a carbon fiber airbox - input appreciated

[JohnJL]

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



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




Filter:
Rectangular K&N filter



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



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...

[Dmitry at Pelican Parts]

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

[Fly911]

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?

[JohnJL]

Originally Posted by Dmitry at Pelican Parts

C2/C4 Airbox Modification / Upgrade


-Dmitry

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

[dsfnctn]

This was a project of mine. i started off building boats at an early age.

[JohnJL]

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

[Rawknees'Turbo]

Originally Posted by JohnJL

That is so cool. . . . Great job!

Agreed - absolutely love it!

[Dmitry at Pelican Parts]

+1 looks absolutely incredible.


-Dmitry

[JohnJL]

Originally Posted by dsfnctn

This was a project of mine. i started off building boats at an early age.

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.

[911pcars]

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

[dsfnctn]

Originally Posted by JohnJL

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.

K&N makes more promises than president campaign speech

[JohnJL]

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.

[dsfnctn]

Originally Posted by JohnJL

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

[GaryR]

Originally Posted by dsfnctn

K&N makes more promises than president campaign speech

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

[dsfnctn]

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

[dsfnctn]

Originally Posted by GaryR

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

Welcome to Rothsport Racing - Engine Products
K&N

[JohnJL]

Originally Posted by dsfnctn

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

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.

[JohnJL]

Originally Posted by dsfnctn

Welcome to Rothsport Racing - Engine Products
K&N

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

[Rawknees'Turbo]

Originally Posted by GaryR

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

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.

[robcf]

Originally Posted by dsfnctn

This was a project of mine. i started off building boats at an early age.

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.