There are a few people running VVT motors in NA miatas here so I thought I would post this even though it isn't turbo related. I have been working on a 3d printed intake duct that draws in ambient air from the front bumper (similar to the joefis intake).
Basic specs for the intake:
*Inlet side has an ID of 65mm, the exit of the intake has an ID of 67mm.
*The total intake tract length from the tip of the duct to the throttle body ends up being about 26" with the ability to shorten the intake by about 2 inches on the inlet side. This is slightly longer than I had hoped, I may end up making a new design that wraps at a different angle for a shorter length.
*The area of any given cross section from the intake should only deviate by a few percent.
*This cost me $35 to print in ABS plastic using a local printer found on MakeXYZ. I can direct people to him if they are interested.
I am uploading the 3d model for people to print their own versions or make alterations to. If you do print one, I would suggest you user either ABS or nylon. PLA will likely fail at these temps. Also, I am considering this a prototype so far. I have been talking with the printer about doing a very thin walled version in PLA, then fiberglass over top, and then solvent melting the PLA away from the model. The ABS version appears to be fine in the short term. The plastic doesn't melt or deform from the heat, but I think getting heat cycled it will eventually become brittle and break.
Dunning Kruger Affect is going to A/B dyno test this over the winter. The part is designed for auto-x where you will be idling in grid with no airflow before launching. My hope is that directly drawing in ambient air will help with IATs at the start of a run.
I am linking to a large image showing the design and construction process. Note that this is printed in several sections and I had the printer focus all finishing efforts on the interior surface. The exterior has not been heavily sanded or vapor treated. Also, that isn't tape at the joints, it's solvent bonded ABS wrap.