Went Through The Entire GXP Airbox Assembly Yesterday... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 06-14-2006, 01:51 PM   #1
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Default Went Through The Entire GXP Airbox Assembly Yesterday...

I took my airbox out completely yesterday to detail it and the engine bay area underneath it as well as just to see what this thing was all about. And of course, I had my K&N Filter ready to install! It was kinda like that Dodge truck commericial for the MegaCab... GEEZ, that'* a BIG airbox! No wonder there is no off the shelf CAI for these things. Anyway, after looking over everything thoroughly and noting the obvious that the tube linking the 2 halves of the airbox was the limiting factor - I decided to remove it all together and give that a try. As I am sure you have all noticed, the tube is a seperate piece from the bottom of the airbox and it simply slides into its grooves and locks into place with a single plastic piece at the bottom. You just remove the lower portion of the airbox - the computer simply slides out and you can place a towel over the engine and lay the computer to the side - you do have to remove that little housing that holds the - not sure but I think it may be the cruise control module(?) up near the fender and kinda above the rear of the airbox - and move it below the STB and back out of the way - also remove the Throttle body and lay it back on the towel as well as you don't have to unplug it - then remove the 3 star headed bolts that hold the lower portion of the airbox in place and slowly and carelfully remove it from the engine bay. You will see there is a small piece of plastic that pushes through from the tube piece and kinda pops into placeon the underside. Just take a pair of pliers and sqeeze the split ends together and it will simply push back through.and the tube is removed. Now, instead of this little bitty 2 inch or so tube feeding air through to the filter - you have an opening you can put your fist through! It is not smooth like the tube - but this much larger opening will allow so much more air to move through it that it seems it can only be benefitial. But if you decide to replace the tube for whatever reason - you can simply pop it back into its original location without anything more than removing the 2 top halves of the airbox.

I know, I know - you want pics. I have a couple as well as a couple of the upper portion of the airbox that is the lid to the filter where I cleaned it up quite a bit with the Dremel near the opening leading to the MAF. I will have to download them and see if I can figure out how to post them. But feel free to email me if you would like me to email you the pics. Talk to ya'll later...
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Old 06-14-2006, 02:03 PM   #2
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I've done this same mod on my Aurora as well. It did make a slight power increase, even on my 3.5L engine. I didn't like how it was designed, either. I took it a step further though, I also removed the walls that were between the two chambers. (the walls that the tube/snorkle butted up against.) I don't know if the GXP has it, but my airbox also had a resonator on the rear of the second chamber that I also blocked off and it gave my intake a more aggressive sound. I have some pics of my process too..

stock, PCM already removed:


Snorkle removed:
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Resonator blocked off:
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Sides removed/PCM reinstalled:
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Later, I have plans to smooth out the inside of the ENTIRE intake box somehow. I'm thinking about using reflectix because of its heat reflective prooperties. It'd make the airflow smoother, and also it would block out engine heat somewhat if applied properly.
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Old 06-14-2006, 02:50 PM   #3
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Nice going Daytona , We have discussed this several times and i kept meaning to get to it. The cold air intake in back of the headlight is so much bigger than that little snorkel tube. This mod will definately help air flow and I'll bet put a little more giddyup in it'* acceleration. and without ruining a nice looking engine bay. The picture was taken while car was being wet sanded before the Custom paint went on.

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I wonder if Caddys have it also or if it is one of the ways N* governed our engine for Pontiac and Buick use. I will definately be getting that restriction out. Use Photobucket to host images, free and simple. After you set up an account use the message board choice, then just click copy and then paste into your message.

And thanx for the photos Custom, The box is so big, I dont know that it needs smoothing and the Maf screen should settle the air right down as well as the filter itself. I bet some metallic faced bubble pack material would do the job nicely inside the box.
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Old 06-14-2006, 03:28 PM   #4
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I too want to some time mod my Airbox to allow more air flow. My two concerns are will this just make more noise and not a noticable difference in throttle response and will the computer eventually retard the timing to make up for the increased airflow therefore eliminating any actual gain?

The northstar is a high performance engine and I am sure thier engineers would have taken any modifcation that helped it breath better into account. I have a K&N filter in the car now and with it I have noticed for the first time about 1 mpg better mpg and better high speed power. I have put K&n in alot of my cars but this is the first car I have noticed a difference in.
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Old 06-14-2006, 03:29 PM   #5
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if you go with an aftermarket MAF sensor (as Im thinking about) you'll want the airbox as smooth as possible. The MAF screens on the N* engines are VERY restrictive. The holes look like pinholes just about literally. That has to restrict air by a LOT on our engines.

Also keep in mind that the GXP airbox was originally designed for the 3.5 and 4.0 Aurora. The 4.6 I would imagine, would have higher air requirements than both the 3.5 and 4.0 Aurora by quite a bit..
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Old 06-14-2006, 03:37 PM   #6
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Quote:
Originally Posted by Custom88

Also keep in mind that the GXP airbox was originally designed for the 3.5 and 4.0 Aurora. ..

I thought the GXP had a Cadillac airbox not Aurora? Same one is in the STS
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Old 06-14-2006, 03:57 PM   #7
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here'* the engine/airbox on my 01 Aurora... They're identical. The STS didn't have an airbox like the GXP/Aurora. They had a one-peice airbox.
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Old 06-14-2006, 04:15 PM   #8
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Custom88 thanks, I learn something new each day. I had no idea how similar the 3.5 and 4.6 engine bays looked.
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Old 06-14-2006, 04:24 PM   #9
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Custom did you notice any performance difference for better or worse after removing the snorkel? I would think that would actually make it harder for air to be drawn in if it was all in a large area as opposed to running through the tube...but i could be wrong...

due to my air box setup i dont really think i want to gut mine, as their isnt much to gut, and i just dont think it would benefit that much.

Its already pulling air from behind the headlight, and I think if i made a big open area for air it would just heat it up more than anything.
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Old 06-14-2006, 04:26 PM   #10
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throttle response seemed to increase with this mod, though it was a small difference. It made the intake sound more aggressive than stock though.
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