AP9engineering

A rare Saab part is now a CAD model.

This started as an idea to preserve the original Carlsson intake duct, but it quickly turned into a full reverse engineering project.

✔ 3D scanned
✔ Rebuilt from scratch in Fusion 360
✔ ~7 prototype prints

The best part isn’t the print - it’s having an editable model that can evolve into future designs like brake cooling or oil cooler ducting.

The full project is now up on my website (link in bio).

ReverseEngineering 3DPrinting

I finally finished a project that's been on my list for a while: reverse engineering the Saab 900 Carlsson front bumper intake duct.

The goal wasn't just to make another copy. I wanted to recreate the original as a fully editable CAD model so I can reproduce it whenever needed and build on it in the future.

That meant:
• 3D scanning the original duct and bumper with an Einstar Rockit
• Rebuilding the entire part from scratch in Fusion 360
• Around 7 prototype prints before I was happy with the fit

One thing I didn't expect was discovering that the original ducts and even the bumper itself aren't perfectly symmetrical.

I wrote a full article covering this process

👉 https://ap9engineering.com/saab-900-carlsson-intake-duct/

I'd love to hear what you think. If you own a Carlsson, would you keep it as is or be interested in some actual ducting to the brakes or oil cooler? Or you prefer the fog lights entirely?

Reverse Engineering the Saab 900 Carlsson Air Intake Duct - AP9 Engineering One of the things I enjoy about reverse engineering is that, once you’re finished, the part isn’t just another reproduction but it’s a design you own. That’s what led me to the Saab 900 Carlsson air intake duct. I’m planning to produce a small number of carbon fibre Carlsson bumpers, and r...

The shop is open!

After a few years of selling parts through messages and emails, AP9 Engineering finally has its own website.
First of all, thank you to everyone who’s supported my work so far. Your trust is what made taking this next step possible.
The website is more than just a shop. I’ve also started a blog where I’ll be sharing the engineering behind the parts, ongoing Saab projects and the problems I’m trying to solve along the way.
If you’re restoring or maintaining your own Saab 900, I hope you’ll find something useful there.
🔗 Link in bio

The shop is open!

After a few years of selling parts through direct messages and emails, I've finally launched the AP9 Engineering website.

Before anything else, thank you to everyone who's supported AP9 Engineering so far. Your trust and encouragement are what made taking this next step possible.

It's more than just a shop however. I've added a blog where I'll be sharing what goes into developing some of these parts, along with other ongoing Saab 900 projects - the problems I'm trying to solve, the design decisions behind them, and the engineering process. I wanted to share the thinking behind the work, not just the finished product.

Some parts have stayed simple and practical. Others have grown into much bigger projects, because once I get into a problem, I can't stop until I've found a solution I'm happy with.

That's really how AP9 Engineering came to be, and now it has a proper home online.

If you've been restoring or maintaining your own Saab 900 and have run into the same challenges I have, I hope you'll find something useful there.

www.ap9engineering.com

This part started as a problem on my own car.

Original rear hatch trims for the Saab 900 Classic are almost always warped or shrunken — so I developed a proper reproduction to OEM standards.

After testing and installing it myself, I decided to produce a small run.

Saab 900 Classic Hatchback – 3 & 5 door

Available now.
DM for info.

Recreating Saab 900 Carlsson Wheel Arches – A Different Approach

One of the biggest challenges of keeping an older car on the road is finding quality replacement parts, especially when originals are no longer available. That was the case with the wheel arches for my Saab. While there are some great aftermarket options out there that provide affordable solutions, I wanted to take a different approach—one focused on achieving the highest possible accuracy and durability that I can.

The aftermarket wheel arches I previously used were made of polyester resin and fiberglass, which is a common material choice for small-scale production. While it works for many applications, it does have limitations, such as shrinkage, brittleness, and reduced weather resistance. On my car, cracks and blisters developed not long after painting and installation. Instead of trying another set, I eagerly wanted to engineer my own solution.

Finally, just recently, I was able to source brand-new original wheel arches, which allowed me to create precise molds. Using high-heat epoxy and carbon fiber I did just that. From there, I used prepreg carbon fiber and the correct processing methods to recreate these parts with OEM-level accuracy. In addition to the overall shape and curvature even the original part numbers are embedded, and the surface finish is just like the factory parts even though I realise the parts will eventually be sanded and painted over. Still, thanks to the choice of materials and process, these arches maintain their exact shape and exceed OEM durability—handling even extreme temperatures up to 120°C without issue.

For me, these small projects are never just about making replacement parts but also about pushing quality and precision as far as I can.

You know it’s time for an upgrade when your suspension parts look like they belong in an archaeological dig. Since the original control arm bearing anchorages are extinct (or just hopelessly corroded), I've stepped in and started to design brand-new CNC-milled reinforced replacements.

Why? Because with the beefed-up braking system, I need a chassis that won’t fold like a lawn chair under pressure.
Braking hard shouldn’t feel like rolling the dice on whether your suspension holds up. So, I'm making sure everything stays exactly where it should—no surprises, no sudden disassembly. 💪⚙️

Recently created this short video of the process of making the caliper cooling ducts. If anyone is interested in seeing what has gone into making such a part then feel free to take a look.

Making carbon fiber brake cooling ducts Sharing some insight what goes into making rally inspired carbon brake cooling ducts for a restomod project.

Half way update for the front rotor cooling. The new caliper adapter arrived from manufacturing recently and as I 3d printed the duct models in advance I was able to work on making the moulds as well as one of the parts in carbon. Now it was just bolting them on and obviously they fit perfectly just like they do in cad.
This small carbon part here is just half of the rotor cooling duct. The second half will come to life very shortly as well and then I have completed all the hardware for the front brakes. Apart from brake lines and the ducting hoses themselves. I guess I'm not finished with this at all... But I'm getting closer.
All the carbon parts for these brakes are made with prepreg carbon in an autoclave.

I've been designing this brake setup for quite some time now. And things change along the way. A good example here is the brake caliper bracket which I was happy with until I realised that there is not much room in this area to accommodate the disc cooling duct and the best place for it is next to the caliper cooling duct. So eventually a new bracket needed to be designed that in a way integrates the disc cooling ducts which guide air directly to the center of the rotor.
While I wait for this new bracket to be machined I can work on the ducts and create stiff and lightweight carbon versions of those. On the table are MJF printed PA12 Nylon versions which is my go to plastic printing solution due to it's good surface finish and more accurate features.

After this the front brakes should largely be finished. Next I'll dive into creating new brake lines throughout the car while also creating some brackets and routings for the air hoses themselves.