cheap stock airbox mod
 

Hi guys,

I just completed a stock airbox mod for my FD. The results feel really good. The car pulls a lot stronger. I fabricated a shield, opened up the box, threw in a new K&N and that was it. I bet that this mod gives as good a performance increase as the expensive intakes, at a very low cost. When it is done, you can't see it at all, and neither can the smog guys.

Does it look alot like the one I have posted on my web site?
http://home.earthlink.net/~maxpesce/index.html
and used to be in the Forum Galleries when they were working.

It accomplishes a similar goal as yours but is designed a lot differently. It also uses different materials and mounts differently. I don't have a website. or any photos. If enough people are interested, I suppose I will have to get a website together. I don't know much about computers.

Max,

what kind of HP increase did you get when you put yours in? An estimate will do if you don't have any dyno numbers.

I dont have any dyno #s but did notice a reduction of turbo lag and better throttle responce w/ a 0.5<>1psi increase in BOOST, so I am guessing 10<>15hp gain BUT I also upgraded from the stock airfilter to a K&N at the same time as the airbox mod.

The car goes thru the first 2 gears so fast that it is harder to tell. I really feel a big difference in 3rd gear. It seems to pull a lot harder than before. I have not wound it up very far in 4th..........yet

This isnt about me, but I'll share my mod. I went to home depot and bout 17 inches of a thick heavy vinyle tubing. I think it has a 2.5 inch diameter opening. I dremeled a hole in the bottom of the box about the same size as the hose.

I removed the front passenger plastic piece that is in the nose of the car. I routed this flexible rubber hose between my KOYO and the chassis and eventually into the air box. Then I took some 4 inch tin piping and connected to the hose for a large 4 inch opening and sealed the gaps.

Keep in mind that before I did this mod I got 104.8's for my trap and 13.7's in my 1/4. After I did this mod I got 106.5 to 106.6 in my trap speed and 13.50 in my 1/4. (I run 13.0 @ 108 with my nittos now).

Anyway, it costs under 20 bucks and really works. I can tell it works also becuase my air filter is dirty as hell where it touches the hose, so it must be doing something!

Sounds like a good cheap mod. Mine opens a space in the box a lot larger than yours, and the shield pulls cool air in from the front.

I would like to have a larger opening, but it does bring in cold air and it also leaves the stock intake intact so I do get extra air. I'm no expert, but I would guess that there is a bottleneck somewhere in the Manifold or piping that will dictate a maximum amount of air. In otherwords at some point extra air is not going to help (bottleneck). I dont know if I have reached that yet. I have other plans at some point to do additional things to the intake and I will see if it has any difference.

You are right, there is a maximum amount of air that the system can use. I don't know how much that is either. I just want to let it take all it wants without having to suck too hard.

Just installed Adam's mod! It works great. I'm showing about 1PSI of extra boost and can really feel the extra air ... especially when the secondary kicks in. The car is a bit noisier, but it's a pleasant Vroom Vroom ... kind of goes with the Mazda Zoom Zoom ;)

The best part of this mod is that a CA emissions inspection will never catch it! When the air box is re-installed, it's totally invisible.

I have pictures for anyone who is interested. In a few weeks (if only we had 8 day weeks) I'll have my WWW server back up and will post a link.

Adam did a great job with the shield. It’s very obviously hand made, but also very clean. It fit easily and came with instructions for installation. Adam even fashioned the shield to use an existing (and unused) stock pre-threaded bolthole … he included the bolt.

lets see some pics....im interested...

ready for the shield
 

before the shield and with the radiator foam removed

the shield before installation
 

Notice the excellent reading material in the upper left corner ;)

More later ... gota get the door ...

paranoia ques. Is throwing on any type of intake system gonna be okay with out fuel management? Even putting on a high flow filter and the cold air setup that adam is doing, showing an increase in boost or 1 psi? I wanted to do a hardpipe kit with some filters attached for each turbo, but was wondering if this could be a direct contribution to a lean condition, keeping in mind that my car is completely stock, with a DP happening very soon.

There seems to be a consensus that more than two mods (DP, intake, or catback) will put you in jeopardy of running lean. I personally recommend upgrading your fuel delivery before the second mod, especially if you are going to do the third mod anyway.

James, thanks for the nice write-up, and for posting the photos. I would have posted some if I had a digital camera.

Adam

pic three - almost in
 

Ya know … I’m babying a broken o-ring. It’s only a matter of time until I need a rebuild. My goal is to add on all of my performance mods (DP and this airbox) before the rebuild. If I detonate and puke an Apex seal … no big loss, I was going to rebuild anyway. Now I’m saying this as I also bought a PFC piggyback computer from Wade (great guy!), on this forum. Part of my goal is to do my tuning (adjust the computer) before the new motor. Again, the idea is to do it now, when it doesn’t matter if the motor blows. This doesn’t make the airbox a bad idea, it just explains my willingness to try it.

If my motor was in good working order and I didn’t have the PFC to tune the extra 1PSI of boost down … yes, it would make me nervous.

I’ve read all sorts of opinions about how far the car can be modified without a way to manage the fuel / timing / boost, but considering the cost of a rebuild I would go after some sort of boost controller, computer mod, etc. before I went after a DP or intake. Now doing a DP and intake together … forget it. I’ve met a couple of people on the forum that are getting a 12-8-14+ boost pattern from a DP and intake. This is too much for me to rest easy. At the very least, watch your boost gauge …

Anyway, here is another photo. More later … time for bed and posting with photos takes so long!

almost in 2
 

OK ... the last one went fast ... one more ... then sleep!

in and bolted down
 

Notice the bit of duck tape ... I'm paranoid that it’s going to rub threw my radiator hose.

How difficult is this to install? Do you have really user-friendly directions?

drilling the box and instructions
 

I thought Adam's page long instructions were easy to follow, but you do have to be willing to bend and drill the aluminum shield once. Also, the airbox has to be drilled / cut out. Here is another picture ... two more to come as I have the time.

Adam, if you don't mind I'll scan and post your instructions.

Set me up with the template baby! Who is adam and were do I get this dimensions for this work of art! I was going to fabricate a rectangular duct with essentially two of these template pieces spaced the width between the radiator and the frame, but I think this piece is quite nice.

One thing that could be modded to the mod is to provide a bend towards the bottom that helps "ramp" the air upwards.

bottom of the box
 

Adam is the designer and started the thread ... I got mine from him ... you'll have to PM him or talk him into posting the template. He charges $80 for the finished product. I think that it's worth it. Lots of time to desighn this / fabricate it.

He's more interested in sharing his creation than making money, I suspect that he'll let go of the template ... but ask.

Here is another pic ...

I'll cut my own airbox, that's not the prob, I'll even cut the Al. I'd just like the template.

Adam - any chance of giving/selling the template? Could be some easy/quick $ via paypal and don't have to deal with those nasty rough edges & shipping - eew

Personally, because I hate shipping (the outragous rates of places like Mail Boxes etc and the long lines from the "stay at home" moms shipping crap at UPS) I'd figure shipping as being 50% of the hassel.

The problem is the whole IP (intellectual property) issue. Then he would have to make better one's (ceramic coating anyone) :)

OK, it doesn't look too hard with the right tools I guess. Would I be OK if I go to Sears and pick up a rotary tool? Is that all I need?

last pick ... installed less the K&N
 

Ya know ... a drill and file worked just fine to cut the holes in the air box. That's assuming that the shield is taken care of.

James - why did you go through all the extra work and cut those circular holes vs. larger rectangular holes?

Hi guys,

Cutting the stock air box can be done in any number of ways. It looks like James wanted to be sure to keep the integrity of the box more solid, so he left some of the ridges. I used a cutting wheel attached to a drill, and made one large hole. If you wanted to do a "ghetto" cut, you could even use a soldering iron, and just melt the plastic away. Damn, why didnt I think of that the first time. That would work great!!

Adam

The one rectangular hole in my box was an accident ... I slipped while drilling.

The reason that I cut the smaller hole has to do with the ridges that Mazda engineered into the box. Since the engineers felt that the box needed extra structural support (the ridges), I didn't want to remove them. I.E. I wanted to leave some support behind.

There reason that my cuts are round is that I used a drill to do the dirty work ... I.E. the tool cuts round holes by its nature.

When I did my Mod I cut out rectangular holes and left the stock ribbing intact - Figured to keep some structural integrity to the box.

Me thinks the box is quite hardy to hold a filter without the hassel of the holes. Hell - have you used the door handles? They could've used some of those ridges for "additional support".

My Humble $.002 pesos

I kind of wish I had left the ribs, not for support, but for additional protection against large objects being sucked in through the opening...

I didn't feel that there was a structural problem with the box. It seems pretty tough. With the increased flow of air from this mod, the pressure on the box is reduced to almost nothing.

The other benefit form the larger opening is that anything that gets in can easily fall out.......just kidding.

Adam

Good point ... the next time I have the air box out ... Mr. Dremel will meet Mr. Ridge ...

James, Please try the soldering iron. I would really like to know how it works.

Was thinking about it ... I have a cutting tip for my Weller iron ... maybe this weekend.

Soldering Iron
 

Well ... my other half was working late tonight and I took advantage of it.

My 100/140 Watt Home Depo Weller soldering iron with one of it's included cutting tips worked great. It takes some patience and an open area as this makes allot of smoke. :smoker: I've used an iron to cut plastic before and noticed that the airbox is very slow going. I have a feeling this is due to the heat resistant plastic.

Here is a pic of the bottom. Note that I filed everything smooth, the iron left blob-like pieces of melted plastic along the edges.

I have a second installed photo that I'll post tomorrow morning ... unless the forum's server decides to move fast ...

Soldering Iron
 

Here's the installed photo. The next time I'm at Home Depo, I'm going to see what sort of foam they have to fill the gaps between the airbox and the frame. I.E. between the shield's bolt down point and the airbox.

What's the part # of the K&N filter? Also James, how much are those Weller irons at H.D.?

K&N and Iron $$$$
 

If you don't have another use for the iron, you might want to buy a Roto Zip or the like. I.E. something that you'll get some use out of. I happen to use the soldering iron to ... well solder. OK, $$$ I think that it was about $30 but I don't remember. These things last forever so it's worth the $. My dad still has the same model that I do ... it's 20+ years old and works great.

I bought my K&N from Martel Bros . It's the third K&N that I've bought from them. I think the filter is $48. Hard to beat considering that there is no tax and no shipping. Oh and the P/N should be in thier online catalog. It will walk you to it ... just pick Model, Make, etc.

Ok I just got Adam's intake shield. First impressions - it is what it is a bent, cut piece of aluminum. Second, once your intake has little to no exposure to radiator "exhaust". Close to none, I suppose.

Total install time ~ 30 minutes - max. 10 min to remove intake, 1 min to dremel with the router bit from dremel, 1 min to torch the rough edges to smooth them out, 3 min to install, 10 min to replace the intake.

All in all, I am pleased. I did see something similar for 43 dollars on another site, but that was after I spent $80 from Adam. No matter.

From a performance/drivability perspective I noticed the following. Keep in mind that I didn't try driving the car with just the intake holes. I only drove it with the holes & shield.

Previously my mods included:

K&N Drop in
PF exhaust
PF downpipe.

First Impressions:

- Exhaust is now 30%+ QUIETER! Can't explain it other than the car isn't running as rich or something. It is weird.

- Backfires - 85% less. Again has to be associated with the o2 sensor not being able to lean out the combustion. Maybe the disparity of the exhaust & intake was too great. Don't know.

- Time to boost 50% quicker. 1st gear is insane - I was staring at the boost gauge - looked down then noticed I was almost at redline.

- Boost. I'm getting 1psi more. While being pretty careful, I hit right around 11.5 psi -12 psi. (I don't have an ecu, so I am interested in the experts input as to the issues) (the temperature is around 48 F.

- All in all the car is much more "harmonized" probably like it was initially. I'll never know though as I already had the aforementioned modifications prior to me owning it.

-- just to be clear, I cleaned out the entire area - like the above picture - the box is certainly rigid enough to support this small hole. - Plus it looks cleaner.

Comments are welcome.

quieter with new cutout ... and more boost
 

Brentis, I've also noticed that my car is quieter with the larger cutout. The holes that I drilled earlier must have created some sort of weird reverberation.

Also, there was about 1/4 PSI more than before. Enough to warrant one click lower on my PFC computer. For those of you that have one, I presses "1 to lower" once on the primary boost screen and once on the secondary to bring it back to 10PSI.

I'm anxious to try the foam pipe insulation that I saw a few weekends back at Home Depo. I'm hopeful that it will prevent hot air from being drawn as well as eliminate more noise ... I'll let everyone know what the results are

James, Interesting thoughts. With my car, I never had the small holes, only the one larger hole. Needless to say my wife agreed, without me asking. I have the PFS exhaust - must have tuned it with an intake or something.

One thing I did was cover the edges with electrical tape to minimize scraping and any wear. What I found was the resonance of the piece was significantly dampened. You may want to try that. I equate it to the approach of putting a rubber grommet in a tennis raquet.

So do are you planning on putting the foam piping around the coolant piping?

p.s. I don't have a pfc - yet! Tell me - what are your mods? Also why did you decide to get the pfc? Any HP #'s?

I just have a cat back, downpipe, and modified air box. I plan on a mid pipe, pulley, and intercooler. - then I should be done....

With catback, DP, and intake, you should definitely be due for a ECU upgrade. We all say that we will get certain mods, and then we SHOULD be done, but with the FD, that never seems to be the case. A Power FC would definitely be on my Christmas list if I were you.

Thanks 2Furious. I am mixed between a SMIC vs. a power FC. I just spoke to Don at MarvelSpeed and he suggested the intercooler first and the pfc or ecu mod second. He is also a mechanic @ Mazda. He said when speaking with the rx7 design engineers at mazda the car is designed to have peak boost of 8-14 psi depending on temp/etc. He said the boost spike of 15-17psi is what kills the engine. Either way I think I'll be getting them both pretty close together because I'll be paranoid.

ECU and mods
 

Here's what led me to the PFS piggyback ECU. I'll be happy to answer any questions about it. Just remember that I've only had it for about 6 weeks.

My mods so far are (performance only, reliability not listed):
Airbox mod (this thread)
PFS (see the thread above)
Intercooler (planned when the motor is rebuilt)
Downpipe (planned when the motor is rebuilt)

I could probably get away without the ECU, but I don't want to be rebuilding motors every six months. I plan on driving the car (daily) with an 8PSI boost setup and then 10 or 12 for canyon running / stoplight races.

I don't have any HP numbers yet, but I will when TRI point tunes the setup ... after rebuild.

Brentis,

I'm glad you liked the airbox mod. It looks like a lot of good things happened when it was installed. I would like to take credit for all of it..............so I will!! Just kidding. I did the home depot boost controller mod a few weeks ago. It was easy to install, and worked very well. Cost me less than $10. You get an adjustable valve to set the boost where youwant it.

http://www.rx7turboturbo.com/robrobi...controller.htm

If you do this, buy the thicker vacuum hose. That way you can use the existing spring clamps.

How does the car feel now that you have had a chance to get around in it a little?

Adam

http://www.jt-imports.com/U.S.Atop.htm

Hear is another shield. Called the RE cooling panel. $43. Shipping is probably a good bit though.

Brent,

I looked at the shield you mentioned. It is designed to keep the radiator heat away from the airbox, and nothing else. It also allows heat from the rear of the engine compartment to come forward, and blocks airflow from under the car. It's a shield that is placed in a similar location, that performs a completely different function than mine.

My shield keeps the radiator heat from entering the airbox. It also keeps the heat from the turbos and exhaust away from the intake. It allows airflow from the front, and the underside of the car.

Not the same at all.

Adam

Adam I modified my airbox for about $16. It's a bit more labor-intensive than your mod obviously, but it's just as effective. I basically took a 2.75-in. hole drill, and three sections of 2.75-in. diameter accordion-type pre-heater hose from your local auto parts store that extend to a maximum of 18 inches. I drilled three holes in the bottom of the airbox, then inserted the hoses into them (running a few zip-ties on the top so that they can't pull back out). Crawling under the car (up on ramps) after bolting the bottom airbox half down temporarily, I pulled down the three tubes so that one inhales from just outside the plastic bellypan, one pulls air from the hole for the right side oil cooler (don't have, my FD is a touring), and the other pulls air from a small gap (like yours) between the radiator and frame rail. The hose breathing from the radiator gap needed to be pinched slightly so that it would fit into said gap, and it was a bit difficult to get my hand in there to fit the hose into the gap. I have a K&N drop-in filter also, and found similar performance gains to everyone else.
Just thought I'd mention this for those real cheapos out there...:cool: