FD Airbox Build:
 

I'm in the process of making an airbox for my FD. I had the Greddy Airnix kit which fed the turbo only hot air and we all know that on track that's not acceptable. I'm going to get air to it via a NACA duct mounted in the hood and through the bottom of the box.

Here are some pictures of the progress so far:

https://www.rx7club.com/picture.php?...pictureid=3899

https://www.rx7club.com/picture.php?...pictureid=3900

https://www.rx7club.com/picture.php?...pictureid=3901

Looks nice. Where will you be drawing air from?

nice set up.

There's going to be a NACA duct in the hood feeding it directly with another duct in the bottom of the box. I'm going to have diffuser of sorts for the NACA duct for rainy days to direct the rain water down so it won't hit the filter and enter the motor. The bottom duct is there mainly for the rainy days when the NACA duct will be restricted slightly.

Gotcha. It sounded like you were describing two openings and I got confused. But now I understand. :)

Dave

Looks nice so far. I have the same intake and have been planning on doing something similar tailored to my Vmount setup.

How do the filters attach in your current design?
What are those black things?

Thanks, I'm surprised at how well its turning out since I'm new at this fabricating business. I'm going to mount a mesh screen with a filter element on top, I'm unsure of the material of the filter element but I've got some ideas. The black things are actually of the backs of the Greddy filters, I couldn't build a better piece to mount the box to the pipes, I think they are really nice.

Gotcha.

I think K&N will build you a custom filter if you provide the specs. Might want to look into that.

Thanks for the info, I'll check it out.

How about using a couple of Apexi filters inside your box, would it fit?

Nope, there isn't enough room in the box for cone filters. Today I bent up some aluminum screening to act as a backing for a simple foam filter. The foam filter will eventually be replaced by a custom filter that uses K&N filter material. I was going to have K&N make a custom one for me but I've decided to make it myself.

Update: Finished Airbox
 

Here's the finished airbox, I can't get accurate AITs yet since the sensor is still located under the UIM but I'm going be relocating that next week so I'll have the numbers for that soon.

https://www.rx7club.com/picture.php?...pictureid=5573

https://www.rx7club.com/picture.php?...pictureid=5574

https://www.rx7club.com/picture.php?...pictureid=5575

https://www.rx7club.com/picture.php?...pictureid=5576

https://www.rx7club.com/picture.php?...pictureid=5577

https://www.rx7club.com/picture.php?...pictureid=5578

I'm wondering about rain. Do you think there would be any ill effects if you were to drive it in the rain, sucking water into the intake?

Very nice work. A couple of points:

The "black things" AKA velocity stacks will work better if the rounded surface doesn't touch the plate that they're attached to.

Your overall airflow ability is restricted by the size of the hole in your NACA duct. You might get better flow with a duct with a larger opening, and instead of going through a little hole, build the box higher so it's flush with the bottom of the hood and seals with weather stripping or foam or whatever.

I found this article. Hope its useful.
http://www.autospeed.com/cms/A_110281/article.html

Thanks for you're input, I hope I can address your points, let me know how I do and please comment again on it. I'm still learning and like the input. The velocity stacks are actually the backing for the Greddy filters and they were the easiest solution to attach the box to the piping, not ideal but I think they're good enough for now. The NACA duct has a 2.5 inch opening and I think with the flow characteristics of the duct itself there should be sufficient air going to the motor but just in case though if you look at the bottom of the box you can see another intake point which I added, I forgot to mention that with the pictures. You're very right I need to seal it though I wasn't sure how or what I use to make a good seal but as I type this I thought of the solution so I'll post pics tomorrow. Also the box is only about 1cm away from the hole in the duct.

I've decided for now to just cover the duct opening and remove the airbox cover to just let it breath from the engine bay.

Thanks for the link, it was a good article, I wish I had seen it before. The duct according to the formula in the article has an area of 32cm and the second duct (not exact because it is not a a circular pipe) is 7cm for a total area of 39cm. I'm going to look into the device they used for measuring the pressure inside the airbox.