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Cold air intake DIY for Si.

6K views 19 replies 9 participants last post by  Digger 
#1 · (Edited)
Here it is guys, a DIY for making your very own 3" or 3.5" Custom Cold Air Intake. For my project I've made a 3.5" CAI the Cost is roughtly 130$ if you have the tools needed. I hope you guys like it, this is my first write up. If you have any questions do not hesitate to contact me. Product Pipe Copper Muffler Auto part
the almost finished custom CAIFinished product
Here are the parts needed: *45 Degree bend pipe either 3” or 3.5” - 1*U bent Pipe, 3” or 3.5” - 1 ( you can also purchase a J pipe with a U bend and 45* bend)*Couplers, 3.5 straight, 3.5-3.0” Reducer 1 each( you will need two 3.5 straight couplers for ZDX TB)***Because the pipe was fairly cheap I purchased a 4’ section of straight 3.5 inch steel aluminized pipe, This will make good pipe for connectors if you need to use a angled coupler at the bottom of the fender well, if you wish to angle the filter without welding.
Tools needed: -Multi-tip screw driver,-Power Drill(cordless is up to you), -Drill Bit set, -Small flat pry tool, or hacksaw blade (for separating mold), -Hack Saw, or cutting wheel, -Grinding bits, or metal Cutting Bits(I used to expand circumference of the MAF opening) Step 1 Take the U bent pipe cut it in half
Step 2 mock up the angle you will need, Mark and Cut the angle. (as you can see I also did a dry run of the mock up on the couch before I test fit the pipe.)
Step 3. Test fit the System, as you can see the 45* pipe is angled back slightly. I was doing this in an attempt to avoid contact with the radiator hose, which is difficult. You can see where it sits looking through the Foglight opening, some slight trimming is needed. (this will be done soon)
*Making the MAF mount is the trickiest part, and this is my second one so I am a little more confident in my skills. (the first one I made was all hit n miss and I did pretty well.)
*This may seem unorthodox, but I used the Plastic tube the steel stick comes in, it is the same size as the MAF port, put the MAF in there and see for yourself, I then used that plastic piece to create a circle on the piping in the location I desired (pics soon) I drilled a Hole, and then Started to grind the opening to the proper diameter, I basically used the tools I have so it’s nothing complicated.
Almost Fits!
I then used a smaller drill bit, and drilled some holes into the pipe for the putty to grip(I did not break through, just made small dips, you can drill completely through if you wish), and scratched up the surface of the opening in order to try and make a better surface for the Steel Stick to grip onto. *You will first need to remove the top of the stock air box, remove the MAF sensor, rub Petroleum jelly all around the area as a release agent, Johnson’s Wax will work as well.
Then take some Qwuik Steel, or JB weld steel stick, and mix the putty very very well(this part is important or your mold will suck and have no strength) then you will need to press the Mold over the opening, and around the mounting studs make sure you get a good impression of the opening, go inside and flatten the putty so it makes a good shape and fills the opening from the inside.
Wash your hands immediately after handling, if you use bare hands.(the stuff gets hot when it starts to set)Then wait 5-10 minutes but in my opinion you should not pass 15 minutes. The next step is to pry the Mold off of the stock box take care, and pry all sides you will need to use moderate force...
Take said Mold after 1 HR(time to cure, the longer the better) and prep using the Wax, or Petroleum jelly, next mix up more Steel Stick, and fill the MOLD taking care to fill the channel within the impression itself
then Take the Filled mold and carefully place over the opening you cut into the pipe until the circle presses into the hole cut into the pipe.
Clean up excess inside. Then wait 5-10 mins again, next your mission is very very critical, CAREFULLY separate the mold from the freshly set Steel stick or Quik Steel without removing the new Jbweld from the pipe. You can achieve this by using the hacksaw blade or screw driver, work around the edges to release the mold. If you have applied the release agent well enough this will be fairly easy, but it will still take work.
Your next step will be to Even out the Mounting studs, using a grinding bit to flatten down the tops is a great method, or you can use a file, just be sure to take your time. Next you will want to drill small holes(Bit size will be added soon). Then tap the holes with a small thread tapper. If done properly this should yield a product that will hold the MAF firmly in place.For the finishing touch I cut about 2.5" off of the end that goes down into the fenderwell, I feel 1.5 would have been perfect.
A look at the filter placement from the opening for the Fog light.
Removing the bumper would make placing the filter much more comfortable if you have the time for that, but I was in a rush, so I decided to try this.
Remove the lil Pop rivet dealios there are two of them, and the Plastic piece can be manipulated out of its seating to make a hole big enough for the filter to slide in. There you have it. This is how I made my own CAI
 
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#8 ·
Not sure but without air moving freely you probably would have an oiling issue if it were air tight there would be little room for oil to move around


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#7 ·
I am still thinking about that. I will most likely just put on a breather for the time being.

I used a U bent pipe cut in two then I trimmed for the appropriate angle it will all be in the write up.


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#10 ·
Okay like I said I don't know, I don't see how it's off emissions that's no exactly an EGR but perhaps it serves the Same purpose.



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#13 ·
when your motor is cold piston clearance is different as combustion happens and since the clearance between the wall and rings are different you get blow by... now there is pressure in the oil pan and cant escape... so the air trys to find a way out.. if it cant it would just blow gaskets left and right... BUT thats why we have the valve cover breather all this build up leaves right there... unplug that port on a cold start up ur motor is gona throw out air from here as it warms up it the pressure goes down... thats he best i can explain it lol
 
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#15 ·
Its about 6-7 inches away. Updated, still a work in progress..
 
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#19 ·
Its done. Enjoy guys, if you have any quesitons message me. Its easier than it seems, and it works!!!
 
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#20 ·
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