Velocity Stacks & Airbox Prototyping.


This is going to be a big photo dump of my latest adventures into 3D printing, both for prototyping and hopefully end usage. I purchased myself a 3D printer, Wanhao Duplicator i3, and I'll do a separate post for that soon. For now let's talk about my experiences with the intake parts I'm prototyping ūüôā

I have no real knowledge in both 3D printing/modelling and engine intake theory, I'm just learning as I go, so there will be mistakes here and there. And therefore, not entirely sure if these parts/designs will make any measurable performance gains, but it's all fun anyway!

In my last post, I had just commissioned some prints of velocity stacks. Well I did some redesigns, and they can now be found on, again it's still all a work in progress and I'm not expert in the design theory.

The velocity stacks are 105mm tall and designed for Silvertop AE101 throttle bodies.


Next up was designing an airbox for the ITBs and 105mm tall stacks, I pretty much modelled it using the same external dimensions as my Pipercross filter. I did this because I know for sure that it would clear all the brake and clutch parts in the engine bay and I also wanted the ability to easily change from filter to airbox. I can and will make a better design once I have this design fitted and tested.

For the Pipercross filter and this airbox to clear the stacks, a new mounting plate needed to be made. So I chose to print out a spacer that would be sandwiched between two laser cut plates, you can see it in the previous screenshot.


Below is my ideal design, will work on that soon.


The printed spacer for the filter mounting plate, had to be printed in multiple pieces due to the limited build volume of my printer (200mm x 200mm x 180mm).


Before doing the actual prototype print I decided to use some rubbish filament for a test print without support material, just to see how far it could go. It failed pretty quick when it got to the dome part, it recovered slightly towards the end though.


Here you can see the rear section of the airbox being printed, tried to minimise the usage of plastic and support material. This was printed at mostly 200micron layer height and the curved sections were printed at 100micron layer height, varying the layer height like this helps reduce print time as well as reduce support material for the sections with overhang.


Mid section being printed, by far the easiest part. Only needed support material for the mount flanges, this was printed at 280micron layer height.


And this is the front section being printed, all printed at 280micron layer height. This part had some design modifications to improve print-ability, also to reduce plastic usage and support material.


Since this is a prototype for test fitting, sections are glued together using Cyanoacrylate. Final part will either be epoxied or plastic welded together, not sure yet. Or maybe just use the print as a mold for carbon fibre?


It's amazing seeing this all come together as one piece, nearly 500mm total length. So happy!


Photo trying to show the internal clearances with stacks installed, minimum distance to walls is 25mm.


Some lessons I learned during this entire print are that overhangs causes prints to look like crap. So I've made the following design changes to help reduce overhangs.

  1. I added a chamfer on the inside surface to reduce the overhang angles under the "dome", this allows me to print with minimal support material, and the chamfer being only 20% solid means I use less plastic overall.
  2. The highlighted flat sections at either ends of the flange remove the overhangs and allows my printer to simply bridge that section, which my printer does very well. This makes the print look cleaner and also reduce support material.
  3. I found that printing holes on a vertical plane produces nasty overhangs and causes imperfections in and around the hole, so I opted to print only dimples instead of a through-hole. This improves the finish and I can just simply drill the holes post print anyway.



I also modelled this catch can and printed it out for test fitting. Unfortunately, the filament ran out before it completed printing. Was still able to test fit though!


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  1. John that is fucking awesome mate! Can’t wait to see the finished product. I’ve been planning to build a plenum for mine with aluminium but this looks great!

  2. just read the build thread from start to finish, great work. will be buying some stuff in the near future! silly question about the stacks, wouldn’t the front one get way more air than the back?

  3. Thanks Dennis!

  4. Hey Matt.

    From discussions with a few people, apparently that doesn’t happen. And even some airbox designs have a taper with the front being larger than the rear, the photo from Speedhunters shows this really well.

  5. interesting. will read on with interest!

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