Hey guys,

had a student of mine been helping me try to make something. I'm wanting to make an adapter to fit the stock air filter box to a BNR upgraded turbo. I have in the past used an O'Reilly special, just a silicone elbow with some metal pipe in it to go from the turbo to the upper elbow. It looked crappy and took a good amount of RTV to get to be airtight but it worked. Drove this way for many years. I'm wanting to make this adapter to provide a stock-like appearance as well as a direct fit. Here is a picture of the silicone elbow I was using, as well as the initial model for the adapter in green, and the current iteration of the adapter in white. The white one fits well. I just need a couple of small feature adjustments. The question I have is how could we make one? What material is suitable?




If you guys have any ideas on how to make something like this, please let me know. I know its a small amount of people who would be interested, but I think it would be a cool contribution. On a separate note, does anybody have a spare of the ring that goes in between the upper and lower elbow? We moved last year and my engine bay was apart and I cannot find that thing for the life of me.

 

If you need flex, TPU is great if you dial in your printer for it - I've prototyped numerous things that are still in use using Overture TPU including gaskets that see more than their fair share of petroleum products and heat, also a few air box adapters.

If you don't need flex you can both A. get rid of those ribs (unless its for aesthetics) and B. use something like CF Nylon. I've built a few throttle body adapters from Polymaker PA612. Again, your printer will have to be set up to use it properly.

 

It does need a little bit of flex. The three baffles in the middle are to give the inlet duct some flexture since the engine moves in its mounts independent of the chassis. It's that way on the stock elbow as well. It also helps compensate for inconsistencies in manufacturing. I can try printing a TPU version. How do they hold up with the heat and time?

I have been trying to identify the material the stock elbow is made of, but I can't find any markings on mine that would tell what it is. If I knew that, that would get me quite a ways. I do know that it is about 90 durometer Shore A. That and the ribs give it quite a bit of stiffness so the turbo can't collapse it, but it still has some flex. I asked the FD guys if they had any markings on their turbo inlets and they came up with P-TE as the identifier. https://www.rx7club.com/3rd-generati...ation-1167607/. I have yet to match a material to this identifier.

The stock elbows look like they were molded from sheets of rubber squished in a die. The lower elbow has two halves joined at a seam, while the upper elbow appears to have three sections that are seamed together. Buna-N and Neoprene are sold in sheets and could be material candidates.

Again, appreciate all the help

 

if you bought a new duct, it would be way softer. whatever they used gets harder as it ages.

 

a couple of ideas,

HKS made an RS Intake, which won't work, because the casting is 60mm. i wish they would have made the casting 70mm (or whatever) and had a boot to make it fit the stock turbo. the big end is 100mm
3d print out of whatever works in an engine bay


and then this is what Knighsports gave you, maybe its not as simple as it could be

 

Again, Overture TPU will do what you want if you can print it. It's 95 Shore A and if layer adhesion is dialed it lasts in an engine bay as well as resists petroleum products. That said you do still have the option of just piecing together hard pipes and silicone couplers.

 

I'm happy to see people still finding new ways to keep these things on the road.

Once you get the material worked out, you could probably sell a bunch of them in stock dimensions, too. They're all brittle and cracked by now, and new ones from Mazda are $200+.

 

Alright guys, here's an update. I haven't had time to fit this version of the part in the engine bay, but we did get it printed from TPU. We might tune in some settings but this is where we are at right now. Flexture seems like it would work good at room temp. I wonder how flexible it will become at operating temp. So far I'm impressed. Let me know your thoughts, or if there is something we can adjust better. Also, does anyone have a spare one of the internal metal rings that join the two halves together? Mine seems to have gotten lost when I moved houses.

 

Here's an update on this project. I tried the elbow that was printed, as shown above, and it fit pretty good and had good flexure to make everything line up between the turbo and the MAF. I did have some concerns that the large surfaces on the elbow curve would be able to be crushed in once the engine was warmed up. A buddy of mine got a new 3d printer and wanted a good test to get it set up. The resulting new elbow was also printed out of TPU. He did increase the wall thickness and used a gyroid pattern for the few sections that needed infill. This made the print much more rigid, and it feels like it has the same amount of give as the stock rubber elbow. This printer was also able to give a better finish inside and out. Here are some photos of the new elbow, a list of 3d printer settings, and the 3d model files for those of you that want to give it a shot. Let me know if you guys get to try it out!

 

This is great. You did a nice job on the production! On my 6 port Turbo project I ended up using the NA intake tube, flipped it around and attached to my BNR stage 3 turbo. on the other end I attached an AEM cone filter that is resting under my airbox. Everything "looks" OEM as possible under the hood. ' I eventually fabricated an insulated box from 1" thick fiberboard to go around the cone filter assembly and everything still fits under the MAZDA boxlid.

 

Appreciate it. If I'd had your idea, I would have probably done that. I still like the end result. Here are a couple of pictures with the elbow installed

 

Appreciate it. If I'd had your idea, I would have probably done that. I still like the end result. Here are a couple of pictures with the elbow installed