Series 4 owners who prefer to make stuff instead of buying it might be interested in this. It’s part of an article from Autospeed on making a cold-air intake for a Miata. The guy replaced the stock AFM with a Series 4 one and made his own adaptor to fit a 3” ID pod filter.

“The Simota filter uses the ubiquitous 3-inch outlet duct size. While adaptors can be bought cheaply (for about $25) to fit such a filter, I had the materials available to build my own. By notching and pressing a short piece of 3-inch aluminium tube in a vice, the end could be squashed into a match for the RX-7 airflow meter's rectangular intake (the inner circumference of both pieces being almost identical). This provided a very smooth transition with no square edges. This tube was bonded to a flat plate that had suitable mounting holes for the airflow meter, and the adaptor was complete.”

The AFM’s intake is 63mm x 50mm, which give a circumference of 226mm. This is the same as a 72mm circle, so a 3” (76mm) OD pipe with 2mm wall thickness will match perfectly.

This is almost identical to the one I made for my 12AT Cosmo a few years ago, except I folded the transition from a sheet of stainless steel.





And before you ask about that filter, click here.

 

GEE WHIZ WALLY!!!! You mean we have to make something instead of buying it?

Heavy Sarcasism Intended

 

nice nice i like it!

 

this work the other way around wouldn't it?
say you've go no AFM (aftermarket ECU) and you want to keep the std airbox for legal reasons..
its gotta be the same bolt patters just id the 3" pipe clears everything, i guess...

 

Higgi makes some damn nice cast AL adaptors for 20 or 30 bucks shipped. I made mine out of steel (got it free) and would love to give it flight lessons with the addition of a standalone.

Now I just need to win the lottery, but I'm too broke to buy the tickets.

 

I guess so, but if the law says you can't have a pod filter, that doesn't necessarily mean you have to use the stock airbox. The FC's airbox is quite bad, but there are some much better ones around. Late-model Commodore airboxes are a good example, big and cheap.

Jimmy, the point is you don't have to buy one. If you have the tools and material, why wait weeks for one to be sent to you when you can make one in a couple of hours. Besides, some of us just like making stuff.

 

AMEN

 

yeah, good point..
I was going to mod mine by cutting the whole base out of it and making it a bit nicer and also adding a 2nd inlet to the top.. i then concluded that i would be able to make it to the standard i would want due to my dodgy wrist

i just thought i would mention it incase it was of some use for someone out there

My plans have changed yet again as ive just bought a decent FMIC for the 'vert, so I need the room around the std air box anyway.. I'll end up with a pod in some sort of heat sheild that's only open to cold air.

 

hahahaha I have made nearly everything on my car. (so i'm not good enough to make rebuild gasket sets.. who's perfect?)

Higgi makes a kick *** product which might have better results than some peoples attempts at making a 3" tube mate to a 2" square hole. (generalizing here)

You guys havent seen my home made subframe connectors yet.

 

You should've seen the one I made, it was beautiful. It was folded up from 1.5mm SS, and transitioned from 3"dia to 2"sq over a 3" length, and was TIG'd onto a 3mm thick SS flange. I'll see if I can find a photo.

 

Someday I'll have my own tig. I made my adaptor before I got access to the one at school.