DISCLAIMER: This is what I did on my vehicle and had great results with it. However, I am not liable if anything happens to your car because of this.
The airbox/intake modification:
I did this for the performance of course, but the sound that comes with it is unbelievable. You will have heads turning left and right when they hear it. I have not heard another naturally aspirated 12V VR6 that sounds as incredible as this.
Some sound clips:
To prove the gains for this airbox modification, I provided a link of my dyno with such minimal modifications (176whp/177wtq)(http://forums.vwvortex.com/zerothread?id=2899452). My track times also show the success from modifying the airbox. (It's a 14.4 second car and it's near stock).
You are almost definitely losing power with a cone filter, instead of the airbox in place, because of all the hot air that the cone filter is exposed to. Cone filters work on either a cold air intake or when being used with a heat shield. To further prove to you the power loss of a cone filter in place of an airbox, here is a dyno test from Techtonics Tuning of an open-element conical filter versus an airbox. There is quite a drastic loss in power with the conical filter. http://www.techtonicstuning.co...7.JPG
First, buy a high-flow drop-in air filter of your choice.
What I did, and what many others do, is modify the stock airbox. All you really need is a dremel, or maybe a utility knife, if that may work [I used a dremel].
Next, is cutting out part of the front/fender side of the airbox. I used a ruler and straight blade to slightly draw out where I wanted to cut exactly. I used many of the airbox’s lines to cut the cleanest looking cut. Some people swiss cheese the airbox, which in my opinion, is not the best method to go about this. You can just cut a whole clean piece out of the airbox. It will allow more air and look much more professional and clean. You honestly can't tell the airbox is modified if you do it in this manner.
Here is my setup:
Here with K&N panel filter inside...
In the upper airbox, there is a velocity stack'd duct in the upper section of the airbox that I removed. The difference in diameter after removing the duct is noticeable. The bore is quite bigger and the intake pipe now receives more air from the entire airbox panel, rather than a portion before.
To remove air duct, take two flatheads and stick them in between the duct and upper airbox, unplugging the tabs. Leave the flatheads in there after unplugging the tabs. Then, take small pliers and grab a nice hold of the duct and pull out with some force.
NOTICE: Some people say this duct basically acts like a velocity stack and that it helps directs air to the MAF. Velocity stacks do amazing things for air flow, but in this case, I'm willing to sacrifice this piece by looking at the bore of the intake after removing it.
With the velocity stack in the upper airbox...
Without the velocity stack. Notice the difference?
And the velocity stack removed from the airbox.
I removed this plastic honeycomb piece from the MAF. It's there to give the MAF the most accurate readings, but I’ve been running without this piece for a long time without any problems. If anything, I would say it helped. Remember, this piece pops right out, so you can always push it back in if you ever want to re-attach it. It is not a permanent modification to the MAF.
Take the following from someone on the 300zxclub.com forums:
"Removing the mesh on the mass airflow sensor (MAS) will up the boost on turbo'd vehicles a couple pounds....this allows for more air to enter with less restriction...did this on my skyline...probably do some good for NA too.
But... the mesh is there for a reason....the mesh channels the air through the MAS and onto the sensor...without it, there is an argument that the sensor may be getting an incorrect reading...but it worked for me....its up to you...
On the 300ZX if you do the mesh removal, you will increase air volume from 300cfm to about 700cfm. It will increase your boost and your response, and will get rid of most of your hesitation problems...... oh, and it should lean her out a bit too, good for those of you with hight boost.
And iv'e seen articles where LS1's are being dyno tuned with the mesh removed."
That plastic piece removed gives you a straight through MAF…
Remove this duct from the front of the airbox. This piece is pointless now that the airbox is opened up and there is no velocity sucking air from it anymore (imagine a house vacuum with a hole in the pipe...it will lose much of the air velocity that picks up dirt). This pipe just blocks air from the front of the airbox. I removed it completely.
Remove this piece from the fender area. There is no point of it now that the duct is removed. It also gives a little more air from the fender area.
And the result of that being removed is more air from the fender area…
And some shots of how the airbox sits…
Modified by Breezy. at 1:28 PM 9-17-2008