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 🙂

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!



ITB Build – Part 14

Dropped my engine off last week at the Auto Xperts, they did an excellent job and degreed my cams to the recommend specs. Final adjustments will be made on the dyno.

Picked her up this morning and have been on it since than.

After the crank bolt was correctly torqued, I started on assembling the timing cover and ITBs.

Some close-ups of stuff.

Lightened flywheel and clutch going in.

Engine going back in 😀



ITB Build – Part 13


So big update! I finally got my built head 😀

Final specs:

  • 2001 NB6 head
  • Intake camshaft - 280deg 10.5mm lift
  • Exhaust camshaft - 270deg 9.4mm lift
  • Solid lifters
  • Oversized valves
  • Stronger valve springs
  • Fully reconditioned
  • Extensive porting, de-shrouding etc...
  • Port matched

Intake camshaft is a custom billet profile, and the exhaust is a custom regrind.

Haven't had too much time to work on it, but things will move fast next week.

I bolted the intake gasket to the manifold and port matched it using my Dremel, nothing too exciting 😛


ITB Build – Part 10

Update time! Head isn't finished yet so I've been doing a few odd jobs here and there.

One thing I did was start on the brake prop valve relocation. It's not necessary but does give me extra space for the velocity stacks, might be able to increase it's length later down the track too. So I picked up some angle aluminium plate for $5 and started cutting that up.

Cost me $5, pretty awesome deal I thought.

Measure twice, cut once. Came out exactly how I wanted, the prop valve will than be mounted just above the brake booster. I'll get someone to make the hard lines when engine is out.

Here is the capacitor used for the COPs install, it's needed because the battery is in the boot and can cause voltage drops when the coils fire. The capacitor helps by storing a reserve of power and eliminates any voltage drop. Well that's what I think it does =P

Terminated wiring for the AFR gauge, I used Deutsch connectors and braided sleeving.

Ordered these velocity stack booties from Outerwears, quality seems good but I'm not 100% sure they will provide enough filtering. So might experiment with some foam as well.


Car Parts Make Me Wet

^^ True story...

I've been working on a few small things on the car, but haven't completed any of the jobs so won't post up any photos. I have bought some new parts though =)

First up is a new lightened chrome-moly flywheel that weighs 4kg, which is less than half the weigh of the stock one. I actually had a few lightened 1.8L flywheels, but I didn't want to replace my clutch so sourced a 1.6L flywheel instead.

The drill-outs on the outer edge seem a bit weird, but makes sense that any weight on the outer edges would have a greater affect than weight closer to the center.

Next up is my Toda adjustable cam pulleys, these were sourced direct from Japan. They'll be dialed up with my billet camshafts by an engine builder.

The quality is amazing on these, glad I didn't cheap out on this part of the engine.

This is the intake cam pulley, it's slightly different from most other adjustable cam pulleys because it has the three little trigger knobs for the hall effect cam sensor. I believe this type of cam pulley is required for engines from 99 onwards?

The next part was also ordered direct from Japan, it's a KG Works stainless steel tombstone. It comes with the full face plate, hazard/retractor buttons, vent rings, HVAC face plate and gear surround.



Velocity Stack Stickers!

My mate recently had some of these awesome stickers made up, it's perfect for all of us who run ITBs. I've got them on my car now, just gotta wait till the real ITBs are installed haha!


Below is Ian's ITB Daihatsu Mira rocking the stickers. Three stickers because 3-cylinder 😀


ITB Build – Part 1


Started pulling apart my car today, the head is being removed so I can get that ported. The AC, all wiring, intake, strut brace and fuse box will be removed to make way for my custom tucked wiring harness.

I was planning to port it myself but have decided to send it down to Warren Heath Performance down in Melbourne. The head will received an extensive porting job as well as larger oversized valves, stronger valve springs and re-shimmed solid lifters. The camshaft going in will be 280degree duration and 10.5mm lift.

Didn't get too much done today but photos below.

The operating table where most of the work will be done.

Bonnet off, radiator out and headers moved aside.

Valve cover off to remove the head, full port job on the way with massive cams going in.

The AC condenser removed and a pile of parts that won't be going back in.

That's all for today, covered up and put to bed.


ITB Test Install

My new fuel rail finally arrived, had to replace the M-Tuned rail because it had clearance issues with the fuel rail bracket. And I was able to get myself a B6 cylinder head for free. This allows me to test fit all the parts and I can work on the fuel lines and wiring while my NB6 head is away for porting and cams.

Also did a quick test fit of the ITBs to see if there are any issues that need to be sorted out.


ITB Update

In my previous update I posted up about reassembling my ITBs. I had to use new screws to hold the throttle plates as the old ones were drilled out, they were replaced with socket cap screws but I was recommended to use something with a smaller profile head. I've now replaced the screws with button head socket screws.

The screws were also cut down so not much thread was left sticking out on the other side.

Spent some time over the weekend dialing up the ITB adjustment screws, still a few things to sort out and hopefully they won't cause issues down the track.

Stupid little adjusting screws, very tedious!

Finally received my FPR adapter piece for the M-Tunes fuel rail.

Gave the foot-well plate a good clean.


Synchronising Ian’s ITBs

Well word got out that I was in possession of an amazing device (Synchometer), so Ian dropped by with his Daihatsu Mira Van to sync his ITBs. I've never used a Synchometer or played with ITBs before so it was a good experience.

It's a slightly tedious process because adjustments on one throttle body will affect the others, so it can take a few goes to get it right. Once the ITBs are synced though, the idle speed needs to be adjusted too, with Ian's car the idle ended up being higher.