# Cold Airbox Mod



## svede1212 (Nov 1, 2005)

This mod lacks the bling of some of the commercial "C"AIs but from what i observed of them they lacked the "cold" part. they all relied on the stock holes in by the radiator cover and the two small holes below the airbox to bring in air. the kay-n-en and that lincoln feller also both had gaps where they could pull in engine bay air when the stock holes couldn't keep up (there's 12 sq inches of cross sectional area in the tube by the TB. i couldn't find that much in total from the stock holes). i have seen many discussions on many boards and claims by manufacturers about horse power increases, whether thru dynos, seat-of-the-pants, drag times, etc. the tests and measurements to back up those claims and the things that are lacking are the "Air Intake Temperature" (AIT) and the pressure drop at the throttle body (TB). the temp can be monitored thru the AIT sensor and the pressure drop can be measured with a manometer at the TB between stock and various other setups. these are the only things that matter and yet not one manufacturer has ever posted such results. in my stock '04 the restrictions were at the Mass Air Flow (MAF) tube and the MAF sensor. the tube on the '04 constricts down in a small square opening plus the accordian creates a whole bunch of turlulence/resistance. i replaced the tube with a 4" ID smooth bore JHP MAF tube. the MAF sensor may get removed if i go to a speed density tune down the road. i replaced the stock panel with a K&N after the stock had 12,000 on it. i figured the long term cost will be less with a reuseable. in actual manometer testing the K&N panel has a slightly lower resistance but the difference between stock, K&N and no filter at all is negliable. anyways here's what i did to really bring in cold outside air. at the strip i really pull hard in the top end with a best trap of 105.99 MPH with all else being stock except for the shifter.

i drilled a hole where the smaller hole below the stock box was. i used a 3" hole saw and had to wedge a board underneath so the pilot bit could center on something. it intersected with the elongated hole that was already there and i used tin snips to cut off the triangle that was left to make an even bigger hole. that's the garage floor underneath.










Then I hacked the inlet "box". it had a baffle that partly blocked the two lower holes. i used foam tape to insulate everything from engine bay heat.











inlet "box" insulated










inlet "box" in car with the hole down below











Modded and insulated filter box. Note i cut that irritating anchor tab off of the front











This shows the insulated IAT sensor











and the finished "snug-as-a-bug" installation


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## flht3 (Nov 16, 2004)

nice job !!..i will be doing something similar, how much was the aftermarket intake tube ?? and were did you get it.... :cheers


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## fergyflyer (Apr 18, 2005)

I did almost the exact same thing. I like the fact that it retains stock appearance. Before doing it in the heat of the Florida summer, I was running 13.8-14.2 at 103-104. After doing it I ran a couple 13.2 at 107, but the majority were at 13.4-13.6 with nearly identical weather conditions. I also enlarged the hole at the bottom of the airbox and it can pull air from below. I then used weather stripping to block some air from the engine compartment.


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## svede1212 (Nov 1, 2005)

thanks. i've been running 13.3 to 13.5 with it. with my trap speeds i know i can get a lot lower if i can ever hook up. DRs are a must. the rears are getting thin so it will be my first purchase next spring. i used the tape to seal everywhere around the box so it can only pull from outside. i had extra tape left over so i taped up the MAF tube. i don't know if it will stay on in the heat of summer (it's rated for 180*) but if it doesn't work i'll glue it with something else. insulating the AIT sensor is a very good idea. it is in a spot that gets heat from the radiator and i think the insulation will prevent heat soak. the tube i got from JHP (at www.JHP.com). it's an aussie company. eMail them for a price. they don't post prices on their page due to fluxuating exchange rates. they are a good company to deal with tho. i should know what i paid but i don't  . they gave me a good price because i bought my GMM rip shifter from them at the same time (the best first purchase you can make).


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## rushhour (Aug 3, 2004)

Not sure if you need to go that big of a hole - but it can't hurt.

The insulator is a great idea. 

I am have been the 2 hole Monaro CAI also (see my pictures) for a year or so now - it works great. Best time so far with a 04 A4 is 13.364, best top end 105.17. I use the 300 KW HSV tube in conjunction with the modified air box.

I agree though - there are a lot better/cheaper ways of getting the car to breath then the "CAI" kits on the market. The Aussies have been doing this for years.


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## svede1212 (Nov 1, 2005)

yeah, i wanted to make sure i had in excess of 12 sq inches of opening to the outside. as i stated, that's the cross-sectional area of the MAF tube. also as i stated i think the aftermarket CAIs are at best as good as my mod and more probably not quite as good due to the limitied amount of outside air they pull in. the "dyno tests" are the biggest hoot. remember folks the only things that matter are pressure drops and temperatures. i challenge any CAI manufacturer to publish those results.


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## Holden (Sep 10, 2005)

Good post im on board!!! Like JHP also. Thanx for PICs.


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## 6QTS11OZ (Mar 27, 2005)

svede1212 said:



> yeah, i wanted to make sure i had in excess of 12 sq inches of opening to the outside. as i stated, that's the cross-sectional area of the MAF tube. also as i stated i think the aftermarket CAIs are at best as good as my mod and more probably not quite as good due to the limitied amount of outside air they pull in. the "dyno tests" are the biggest hoot. remember folks the only things that matter are pressure drops and temperatures. *i challenge any CAI manufacturer to publish those results*.


I did similar kind of mods to my air box too before I got my LPE CAI. Throttle response is much more noticeable with the CAI though. But seriously, you don't think a major CAI manufacturer would waste their time challenging something as insignificant as this do you?


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## svede1212 (Nov 1, 2005)

no because then they wouldn't sell their over priced stuff. "noticing" isn't very scientific. the insignificance is that they couldn't post anything that would make you part with your money besides the bling factor. i think the noise they make is the seat-of-the-pants that's noticed. before and after dyno runs are taken right at install and not after the comp has had time to adjust after 100 miles. has anyone looked at their "CAI" and looked to see where the "Cold" air it is taking in is coming from? are there extra areas opened up? i just saw the same openings that were there with the stock set up. does it chill the air somehow? do they insulate the AIT sensor? seriously the parts for them are the smoother tube (on an '04, not even that on an '05) and an oversized air filter, the major "restriction" in the path is not the air filter but the MAF sensor. tests have been done with stock filter, K&N and no filter. the K&N is almost like no filter. the air box on the stock setup is not sealed well against engine bay air but neither are the aftermarket ones. the ones i looked at had small gaps by their sides. you can seal the stock one a lot cheaper. with the lincoln feller you do get that cool little window tho. i think we should all get them because everybody's doing it.  if you have money to burn, follow the got to have it factor and like bling, go for it. i'm saving the money i spend on my car on something that makes it go faster.


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## 6QTS11OZ (Mar 27, 2005)

svede1212 said:


> no because then they wouldn't sell their over priced stuff. *"noticing" isn't very scientific*


I don't think that most are worried about theories of operation or scientific explanations. Who cares how it works? I just want it to work. When someone make comments on their installed performance parts, mods, or whatever the first thing they say is they "noticed" or didn't "notice" any gains. Not, "Oh I wonder if the molecular bonding was adequately rotating at the projected force from turbulent input.... Why make changes if you're not expecting to "notice" any improvements? But as always, to each his own.


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## flht3 (Nov 16, 2004)

i agree !!!! just like the 80.00 plug wires... do you honestly think they make a difference?? hell no !!!!! also.. bolting on a non funtional, scooped hood..just doent seem right...adding heavy rims also kills me...and lastly..the reduction pullys{which acually add some hp} with a whopping stereo..and a conventional water pump..you can see your lights blinking with the bass, as you overheat in traffic !!!


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## svede1212 (Nov 1, 2005)

ok, i noticed a...
Best ET/MPH: 13.385 ET, 105.99 MPH, 2.067 60ft
Best 60ft: 13.391 ET, 104.85 MPH 1.981 60ft
... on stock tires :cheers


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## rushhour (Aug 3, 2004)

The bottomline is what works on the street & track. 

Like svede - I just use a modified stock airbox (you can see my setup in the pictures section). The only thing I didn't do is put a hole in the bottom & insulate the tube (this will be fixed - great idea). I did spend a lot of time sealing up the piece in front of the airbox to keep the heat out. Total cost to me about $135 - mainly the cost of the HSV tube. 

With the set up & tune - I have hit a 13.364 @ 104.77 and also had a 105.17 in an 04 A4. Historically - even on hot & humid days I have always been in the 13.7-13.9 range. So the stock box is doing it's job. Not to many guys with aftermarket CAI's beating me, unless they are running cams & heads of course.


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## PhantomGTO (Dec 8, 2004)

anybody notice the gap under the front lip of the hood?? has anybody made something that would draw the air from there? there isn't much room, but made properly, i would think it should work well.


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## svede1212 (Nov 1, 2005)

that gap is where the inlet on top of the radiator cowl is drawing from. for those of you you like to think about such things remember that bends and surface area greatly restrict air and you need in excess of 12 sq inches. there are companies that make over the cowl intakes but although they look cool and like they would work they have been impartially tested and don't work that well.


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## 6QTS11OZ (Mar 27, 2005)

flht3 said:


> i agree !!!! *just like the 80.00 plug wires... do you honestly think they make a difference?? hell no !!!!! * also.. bolting on a non funtional, scooped hood..just doent seem right...adding heavy rims also kills me...and lastly..the reduction pullys{which acually add some hp} with a whopping stereo..and a conventional water pump..you can see your lights blinking with the bass, as you overheat in traffic !!!


It truly amazes me that there are so many performance specialists on this forum. If you think that 8 or 9mm aftermarket wires by Accel, MSD or JBA doesn't performed better than stock you really don't know as much as you think you do. Most of you think that if a product doesn't give you gobs of horsepower then it's not worth it. It's not always about horsepower. What happened to *quality*? Or a product that will last longer? There have been many tests on K&N filters versus stock filters. And on most tests that I've seen there have been very little or no performance gains for the K&N. But with the K&N, I don't have to buy another filter as long as I own my car. So the cash I save is more important the lack of horsepower I'm getting. If I were to make my own thought out changes to my car for performance gains, then cool, I open myself up for debate. But to challenge a *proven* aftermarket company on their product is amazing.


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## Guest (Nov 7, 2005)

I agree. But you have to understand where they are coming from 6QTS. Granted if you get wires, an air filter, a muffler, and some pulleys, you will NOT run 11's but by the same token, if you buy a GTO and add 1000 pounds of stereo, ground effects, neon, and a grocery store spoiler, you wont be as fast as stock either, MUCH slower.

What these guys need is guidance, which is why people like us are here, to help them. I prefer to educate, instead of intimidate, and with a little instigation, these guys can learn from us and realize what DOES make a difference and what is just an appearance mod, with no performance gain at all.

Just me .02


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## svede1212 (Nov 1, 2005)

got the K&N panel for just such reason, didn't get the "C"AI 'cause i didn't want the appearance mod. this thread was to show some that cared about such things that just as good of result (or perhaps better with cooler air) can be obtained for less money, keep the stock look and have fun in the process.


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## svede1212 (Nov 1, 2005)

6QTS11OZ said:


> challenge a *proven* aftermarket company.


i thought you didn't care about facts. proof is AITs and pressure drops. show them to me


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## Guest (Nov 7, 2005)

And we all appreciate your efforts and ingenuity! At least, the die hard racers do...

:-D


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## 6QTS11OZ (Mar 27, 2005)

svede1212 said:


> i thought you didn't care about facts. proof is AITs and pressure drops. show them to me


Look, I'm not here to prove anything to no one. Just stating my opinion. And opinion is all it is. And not one time did I say anything about caring about facts. I spoke about "noticing" versus "scientific". This shouldn't become a pissing contest. If you're happy with your mods that's all that's important.


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## svede1212 (Nov 1, 2005)

i didn't post this to start a debate either. it was for the stated reasons. there are tons of people with "C"AIs, several of my acquaintences have them and that has allowed me to think it over. i don't think they are fools but i saw the strengths and weaknesses of the commercial setups. the biggest weakness was that they don't pull in any more cold air than stock. if they're happy with them fine. if others would like to see things a different way and not accept things on face value but dig deeper, then i hope to have them thinking. expert? no, but i have researched, looked over and drive a '04 GTO. opnion is one thing, stating that something's proven just begs for the proof. enough said.

peace


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## flht3 (Nov 16, 2004)

first off...a couple less ohms per foot, on an aftermarket wire dont mean squat, on a ignition thats allready more than nessassary...and your stock wires will last a LONG time...the only reason for a increased ignition is a blower or a turbo, as the charge is more dense with these...AND the plug wires are super short..it used to make a difference when a wire was 3 feet long...so you might want to rethink your ideas????you could go out and get a titanium set of rods...are they better...yea...do they make a difference...NO...unless your building a full race motor ??????? :cheers


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## 6QTS11OZ (Mar 27, 2005)

flht3 said:


> first off...a couple less ohms per foot, on an aftermarket wire dont mean squat, on a ignition thats allready more than nessassary...and your stock wires will last a LONG time...the only reason for a increased ignition is a blower or a turbo, as the charge is more dense with these...AND the plug wires are super short..it used to make a difference when a wire was 3 feet long...so you might want to rethink your ideas????you could go out and get a titanium set of rods...are they better...yea...do they make a difference...NO...unless your building a full race motor ??????? :cheers


Cool. You've rebutted my last opinion. Point well taken. Let's move on. :cheers


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## Guest (Nov 8, 2005)

damn its cold today!


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## flht3 (Nov 16, 2004)

6QTS11OZ said:


> Cool. You've rebutted my last opinion. Point well taken. Let's move on. :cheers



sorry man... its just that you kinda called me out, on that wire deal..... :cheers


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## Guest (Nov 8, 2005)

Brrrrrrrrrrrrrrrr, chilly in this office.


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## 6QTS11OZ (Mar 27, 2005)

flht3 said:


> sorry man... its just that you kinda called me out, on that wire deal..... :cheers


Trust me. I don't agree with you. We just need to move on... again.

You're right big_mike. It's chilly in my office too.


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## svede1212 (Nov 1, 2005)

how far we've strayed from my mod...


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## Supersoldier (Aug 24, 2014)

I really hate to wake up a 9yr old thread. But Ive had my goat for almost a year now. I'm still rocking the stock air box. And just by reading I've done most of the air box mod accurately. However I still need to drill a hole in the fender behind the fog light. Trying to be as close to what SVED did it's been blinding without the pics. Or at least I can't seem to get them to pill up at all is it possible for them to be reposted so that I can finish it up. I'm hoping doing this will allow me to have a bolton H/C car without having to buying a cold air intake because of restrictions. Thanks.


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## svede1212 (Nov 1, 2005)

Those pictures were stored on a sever that went out of business. I don't know if I stored any of then locally. I'll try to look. In the mean time I can try to answer any questions


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## Supersoldier (Aug 24, 2014)

Thanks, I did cut my airbox the bottom portion of it but it's more toward the engine side which is where I think I made the biggest mistake. I may try to seal that side off with a piece of sheet metal or just use a holesaw to drill a hole behind the fog light to offset the engine heat some. Also I relocated the factory IAT to the front of the airbox behind the filter. I also put insulation tape on the side of the airbox that's facing the engine. I also replaced the MAF pipe. Is this somewhat on par with what you did?


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## svede1212 (Nov 1, 2005)

Yes although I drilled a 4" hole in the triangular flat piece behind the headlight. I kept adding to it with even a "scoop" below it to catch air under the car.


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## Supersoldier (Aug 24, 2014)

Thanks, I believe I've got everything squared away. At this point all I'm missing is the fast acting IAT & I'm not so sure I need that with my IAT sensor relocated to the front right of the airbox behind the headlight.


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## svede1212 (Nov 1, 2005)

Well the idea behind that is the incoming air will not be the same temperature all of the time. When sitting for instance at a traffic light or starting tree temps will rise and the sensor body gets heated up. When you get moving (especially like a race) the incoming air will cool down quickly but the mass of the sensor will lag in the reading of that cooler air. A faster acting one will help get correct fueling and timing closer to real events. It's not a huge deal but let's think of the 1/4 mile. If the sensor lags by 15 seconds the race is already over.


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## Supersoldier (Aug 24, 2014)

I see, then I will definitely get one of those on order then. Thanks for the advice!


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## Supersoldier (Aug 24, 2014)

Okay, I used a holesaw & drilled a hole behind the fog light. I also ordered the 3000ohm thermistor I believe it is & modded my IAT. All I can say is it made a believer out of me lol. I know it's cold outside however before I could put the gas to the floor and light the tires up without popping the clutch when first driving out. As time went on driving I couldn't break them loose like that to save my life. Now the car consistently smokes them with ease after sitting in traffic like I do at times. I'm definitely satisfied & am sure This modded air box setup won't hold me back once I get my cam.


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