A typical carbon fiber cold air intake requires expensive tooling to make, including machined matched aluminum tools and a custom bladder. An individual requested we make a beautiful intake for a 2010 Mustang GT as quickly and inexpensively as possible.
Using just some cardboard and MDF board, we mocked up the general shape we were looking to create and made sure it would fit inside the car. Our friends at Ozzy Motors lent us the car for one day, so it was important to make sure we got these all right before we had to say goodbye to her.
We transferred the dimension of the filter outlet and the throttle body inlet onto the two pieces of ¼” MDF and then sanded them to the correct size. We did this so that we could ensure that the final carbon part would fit exactly onto the necessary components.
Starting with a large block of high density foam, we drew out the general shape of the intake, including both end dimensions, and began trimming down the edges. It is important to go slow here so that you don’t cut out too much material off. It is a whole lot harder to fill holes than sand high spots.
After a bit more work with the hand saw and surform blades, the part began to take shape. Once the dimensions were close, it was test fit in the car to see where it interfered with other components and where it needed to be trimmed down.
A few iterations of this and the part was ready to go! All dimensions lined up and a quick final sanding left the foam plug looking just how we wanted it.
A plug is typically sprayed in a sanding primer and then sanded to final perfection. One gallon of this primer typically costs $130. A tricky way to save some money and still get a nice surface finish is to use electrical tape. Electrical tape acts as a release film and no epoxy will stick to it so it is great for many composite applications. In this instance, we wrapped the entire plug in it, making sure each layer overlapped so that no foam showed through (of course we somehow missed a small spot...).
Missed a picture here, but if you look closely at this picture you will see that the end of the plug is now bulked up and changes contours. These were two additional pieces of foam sanded to the shape of the MDF boards so that the end of the part would be flat. This allowed the hose clamp around the rubber seals to sit properly on the final part.
With the plug ready to go, it was layup time! Before getting the carbon wet, we cut the carbon to the perfect shape so that it would wrap around without too much overlap. On this particular intake we used three layers of 6K twill carbon fiber. We did the first two layers on this first layup, and then followed with a third layer to cosmetically skin it. All excess carbon was trimmed so that limited wrinkles would be introduced to the part.
The part was then placed in an envelope vacuum bag and sealed. We used a 4:1 epoxy resin system with a medium length cure time so we left the part under vacuum for approximately 4 hours and then let it sit for an additional 10 before opening.
As mentioned above, we planned to do one final skin layer after the first two had cured. This gave us the opportunity to sand any wrinkles out of the first two layers so that the final layer would be perfect. The image below is of the part after one round of sanding.
The final layer was then applied in a single vacuum bag with no additional release or breather bleeder. This method allows for the vacuum bag to be spread tight across the part and wrinkles eliminated. We also made sure that the seam of the carbon and the vacuum bag were on the bottom of the part with the vacuum port on the open end.
The result directly out of the bag follows. As can be seen, the surface finish is decent, but one last sanding and a clear coat will make it truly shine.
Of course, it’s hard to use an air intake if it is full of foam. The next step required removing all the foam from the inside with drills and hand tools. Once started, the electrical tape could be used to help peel the remaining material out.
The interior can be seen in the following picture just after the electrical tape was removed. It creates a slightly ribbed surface finish, but that can be quickly sanded smooth with some light sand paper.
With the foam removed and the interior walls cleaned up the part was ready for a final trim, fitting, and some clear coat.
As the part is used within the engine bay of this Mustang alongside a 4.6L V8 engine we knew it would get a little warm. For this reason we decided to do the final clear coat in 500oF rated Engine Enamel. This would provide an extra layer of protection for the carbon as well as a nice sheen!
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