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Scratchbuilt L6 EFI Intake Manifold

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After a heap of procrastination, I decided to have a go at a carbon fiber plenum...






CF has a number of attractive qualities that make it a nearly ideal candidate for manifold use. Aside from the obvious weight and thermal advantages, it has a nearly unlimited fatigue life. Fatigue resistance is one of my primary motivations as a boosted plenum is subject to significant stress. A well built CF plenum should survive many lifetimes. Add in nearly infinite shaping possibilities and an audible resonance that can't be duplicated by any other material.


Of course CF comes with its own drawbacks, mainly cost, manufacturing complexities, and a limited heat range.


Anyhow, the first step is to build a plug that mimics the final shape. A mold resembling the 'silhouette' was constructed, filled with 8lb expanding foam, and the plug extracted...

















Next up, hand shaping...

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One of the critical elements of the plug is the TB interface. A bonded aluminum flange is the plan (a proper bond will shred the CF before the adhesive fails). Dimensionally, I have some wiggle room in machining the flange to final diameter. But, the plenum needs to be ROUND for the adhesive to work correctly. An easy way to get it close was to remove the backside of a hole-saw, and power by hand...









Its not *exact*, but its close enough to finalize during the finishing steps.





Blended in the new inlet...












About another hour or two of roughing in and it will be time to start the finishing stages.

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Fortunately, I came to my senses and realized I was making this harder than need be. New strategy...






As round as round gets.


Where the aluminum 'cap' begins is where the CF will visually end and the TB flange begins. This will give me a short, perfectly round neck to bond to.

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Was it scrapped for a different design?


Yeah, it was scrapped for a BMW manifold...














The CF plug is sitting high on a shelf. When I'm feeling nostalgic I may pull it down have another go at it. The BMW conversion comes first, as well as one other large project, so it may be a few decades :wink:

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